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Permanent-Magnet Optimization in Permanent-Magnet-Assisted Synchronous Reluctance Motor for a Wide Constant-Power Speed Range
Abstract
A permanent-magnet (PM)-assisted synchronous reluctance (PMASR) machine exhibits both high efficiency and high flux-weakening (FW) range. However, the best performance is achieved after a machine design optimization. In industry applications, the design of PMASR machines requires to satisfy an increasing number of limitations. The key points are lamination geometry, material property, and control strategy. This paper analyzes the influence of PM volume (flux level) on the motor performance, although lamination geometry and stack length are kept fixed. Thus, the PM volume inset in the rotor is optimized. The considered PMASR motor is designed for a very high FW speed range. The study is based on a finite-element (FE) analysis. The accuracy of the FE simulations is verified comparing their results with measurements on a prototype. The FE model is then used to study the different cases.
... On the other hand, it is also renowned for poor power factor (pf) and torque ripples [8,9]. The PMSynRM has a combination of reluctance (dominant) and magnetic torque components with improved pf and torque ripples in a compact size compared with its counterparts [1, [10][11][12][13][14][15]. ...
... PMSynRM exhibits better machine characteristics in all aspects with wide constant power speed range (CPSR) [12,15,16]. An optimized rotor flux guides, PM size and proper placement can compensate the drawback of synchronous reluctance motors [17,18]. ...
... On the other hand, if the machine is not properly optimized, it can have higher cogging torque. It also produces a high voltage at the terminal end due to the larger constant power speed range (CPSR) as the controlled fluxlinkage at this region may be less than the PM induced flux-linkage [9,15]. The drawbacks of PMSynRM can be overcome by adequate optimization of the anisotropy model and properly placing PMs. ...
This paper presents the characteristics of permanent magnets in a synchronous reluctance machine by employing analytical and finite element methods. Four possible designs are studied and their characteristics are compared against a base synchronous reluctance machine with linear barriers to reveal machine characteristics. Then, the paper proposes a novel optimization topology to optimize permanent magnet synchronous reluctance machine as a single object for better machine performance. An explicit investigation is conducted to reveal the operational behavior of the machine such as torque, power factor and torque ripples with various machine parameters and compares them with the base design. The study reveals that permanent magnet synchronous reluctance machine can be optimized to have significantly high-power factor and torque with acceptable torque ripples.
... synchronous reluctance machines SyRMs, [1]) or to the high torque density, power factor and/or high constant power speed range when the internal structure of the rotor presents one or more permanent magnet (PM) layers (i.e. permanent magnet assisted synchronous reluctance machines PMaSyRMs) [2]- [5]. ...
... where B r is the PM residual flux density, w i P M and h i P M are the PM width and height and µ P M is the PM permeability (which is consider to be constant regardless the load conditions). The resolution of the magnetic circuit can be performed still adopting the procedure described in the section II and using (5) where F also include the PM contributions in terms of magnetomotive force. ...
This paper proposes an accurate hybrid FE-analytical model for synchronous reluctance machines with and without permanent magnets capable of taking into account all the machine non-linearities. The hybrid approach consists in solving the d- and q-axis magnetic equivalent circuits in a non linear fashion so to consider the saturation effects. The cross-coupling effects are taken into account by adjusting the analytical flux maps with the results obtained FE-simulating few operating points in the full d-q current plane. The proposed approach allows to obtain an excellent estimation of the direct and quadrature axis fluxes for a wide range of operating conditions including the overload ones with a negligible computational effort when compared to a full finite element approach.
... However, because of the high cost of rare-earth PM, the objective to achieve high torque density by minimizing rare-earth materials and acceptable anti-demagnetization ability has been a critical concern. Many types of motors have been studied for this purpose [5][6][7][8][9][10]. Kim et al. [5] compared interior PMSMs with different PM shapes and dimensions to evaluate torque density. ...
... Multi-phases PM motors, e.g., a six-phase interior PMSM (IPMSM) [7] and a nine-phase consequent pole PMSM [8] were proposed with higher torque density compared to three-phase PM motors. Barcaro et al. [9] optimized PM volume for two PMa-SynRMs (i.e., one with rare-earth PM and the other with ferrite PM) to achieve a torque per stack length of 40 Nm/m and 15 Nm/m for low and high speed, respectively. Bonthu et al. [10] proposed and compared external-rotor PMa-SynRMs between rare-earth-free and rare-earth cases to satisfy the high torque and power density requirements. ...
This paper investigates the flux intensifying (FI) feature of permanent magnet assisted synchronous reluctance motor (PMa-SynRM) in order to achieve high torque density with a small amount of permanent magnet (PM). This motor is thus denoted “FI-PMa-SynRM”. The performance of the developed FI-PMa-SynRM is compared with that of two other counterparts, i.e., an inset surface permanent magnet synchronous motor (SPMSM) and a synchronous reluctance motor (SynRM) to highlight the strengths of the FI-PMa-SynRM. In addition, an analysis on partial demagnetization and torque density of the developed FI-PMa-SynRM is conducted to demonstrate its advantages. The finite element method (FEM) is employed for the analysis in terms of flux linkage and inductances so that the effectiveness of the FI characteristics is validated. The analysis shows that a high torque density (24.79 Nm/L or even greater) can be achieved with a small amount of PM (0.72% motor volume). The ability of anti-demagnetization is also fulfilled. Furthermore, experimental results are provided to validate the analysis findings.
... The optimization of electrical machines is a multi-objective, multi-physics, highdimensional, highly non-linear and coupled problem challenging both industries and research communities [1][2][3][4][5][6][7]. An electrical machine dedicated to automotive applications, has to be designed against driving cycles rather than against one single point [8]. ...
... In the same way of reducing computation time of FE calculation, some approximate models have been developed such as response surface models (RSM), radial basis functions models (RBF), Kriging model and artificial neural network models [7]. Response surface models (RSM) is the most popular optimization methodology to design an electrical machine for EV/HEV. ...
This paper presents a comparison between two design methodologies applied to permanent magnet synchronous machines for hybrid and electric vehicles (HEVs and EVs). Both methodologies are based on 2D finite element models and coupled to a genetic algorithm to optimize complex non-linear geometries such as multi-layer permanent magnet machines. To reduce the computation duration to evaluate Induced Voltage and Iron Losses for a given electrical machine configuration, a new methodology based on geometrical symmetries and magnetic symmetries are used and is detailed. Two electromagnetic models have been developed and used in the design stage. The first model was the stepped rotor position finite element analysis called abc model which considered the spatial harmonics without any approximation of the waveform of flux linkage inside the stator, and the second model was based on a fixed rotor position called dq model, with the approximation that the waveform of flux linkage inside the stator was sinuous. These two methodologies are applied to the design of a synchronous machine for HEVs and EVs applications. Design results and performances are analyzed, and the advantages and drawbacks of each methodology are presented. It was found that the dq model is at least 5 times faster than the abc model with high precision for both the torque and induce voltage evaluation in most cases. However, it is not the case for the iron losses computation. The iron loss model based on dq model is less accurate than the abc model with a relative deviation from the abc model greater than 70% at high control angle. The choice of the electromagnetic model during the optimization process will therefore influence the geometry and the performances of the obtained electrical machine after the optimization.
... En la Tabla 1 se dan los valores de un IM y de un SynRM semejantes, ambos de clase de eficiencia IE4. En esa tabla se muestra que, si bien el SynRM tiene una eficiencia mucho más alta, presenta un factor de potencia notablemente menor, y una corriente nominal marcadamente mayor, con la consecuencia de necesitar un AFV de mayor capacidad y consecuentemente, de un costo superior (Viego & Gómez, 2018 El tipo ferrita logra menos incremento de la eficiencia y del factor de potencia, menos reducción de la corriente, aunque tiene un mayor riesgo de desmagnetización debido a su menor fuerza coercitiva (densidad remanente de flujo aproximadamente menor a 0.5 T) que los basados en tierras raras: NdFeB (aleación de neodimio, hierro y boro), SmCo (imán de samario y cobalto), etc. (Barcaro, Bianchi & Magnussen, 2011;Vartanian, et al., 2012;Baka, Sashidhar & Fernandes, 2018). ...
... . Motores sincrónicos de reluctancia asistidos por imán permanente para arranque directo a la línea con cargas constantes Con el objetivo de lograr arrancar los SynRM y los PMa-SynRM directo de la línea cuando se opera con cargas constantes (evitando el empleo de AFV o arrancadores suaves que resultan muy costosos), se han desarrollado el DOL Start SynRM (Barcaro, et al., 2011;Gamba, at al., 2013;Abramenko, Petrov, et al., 2017); y el DOL Start PMa-SynRM (Kurihara & Rahman, 2004;Mingardi & Bianchi, 2017;Viego, et al., 2020). ...
A basic comparative study on construction characteristics, fundamental parameters and some applications of high efficiency synchronous motors without windings in the rotor was carried out. These are, for variable speed loads driven by variable frequency drives, synchronous reluctance motors and synchronous reluctance assisted by permanent magnet. For constant loads with direct start to the line, reluctance and reluctance assisted by permanent magnet were developed. The latter was studied briefly. A case study with economic analysis was conducted for a Cuban company, demonstrating substantial savings compared to the use of a high efficiency asynchronous motor.
... In the existing literature, several different studies on reviewing/ comparing the electromagnetic performance characteristics of different machine technologies can be found [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Different electric machine topologies have been compared and it is concluded that the PM machines, particularly having IPM topologies, are one of the best rotor topologies suitable for the electric vehicle (EV)/hybrid electric vehicle (HEV) and aerospace applications [5,6]. ...
... In addition, it has also been shown that the PMaSynRMs has also comparable performance characteristics with IPMs, particularly when the cost becomes more important criteria [5][6][7]. The influence of winding structure, magnet shape optimisation, using much cheaper rare-earth magnets; such as ferrite, different rotor topologies, flux barrier geometry optimisation etc. on the performance characteristics have also been investigated [7][8][9][10][11][12][13][14][15][16][17][18][19]. It has also shown that the switched reluctance machines namely DSRMs has also potential to be used in the aerospace applications [20][21][22]. ...
A novel winding topology comprising semi-overlapped windings has been proposed in this study. The main
advantages of such winding over conventional-distributed (overlapping) and fractional-concentrated (non-overlapping) windings
are having very short-end winding lengths and significantly low magnetomotive force harmonic content, respectively. The key
design rules, basic properties, and other merits and demerits of the proposed novel winding topology are justified. The key
performance characteristics of the proposed winding topology are disclosed through an interior-permanent magnet (IPM)
machine. The obtained electromagnetic analysis results are compared with those of other IPM machines having conventionaldistributed
and fractional-concentrated windings. It has been demonstrated that the proposed winding topology promises
significant superiorities such as improved efficiency with substantially reduced total axial length, low eddy current losses, and
low risk of irreversible magnet demagnetisation over other winding topologies. The analysis is verified by finite-element analysis
results and experiments on a prototype novel semi-overlapping winding IPM machine.
... In the existing literature, several different studies on reviewing/ comparing the electromagnetic performance characteristics of different machine technologies can be found [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Different electric machine topologies have been compared and it is concluded that the PM machines, particularly having IPM topologies, are one of the best rotor topologies suitable for the electric vehicle (EV)/hybrid electric vehicle (HEV) and aerospace applications [5,6]. ...
... In addition, it has also been shown that the PMaSynRMs has also comparable performance characteristics with IPMs, particularly when the cost becomes more important criteria [5][6][7]. The influence of winding structure, magnet shape optimisation, using much cheaper rare-earth magnets; such as ferrite, different rotor topologies, flux barrier geometry optimisation etc. on the performance characteristics have also been investigated [7][8][9][10][11][12][13][14][15][16][17][18][19]. It has also shown that the switched reluctance machines namely DSRMs has also potential to be used in the aerospace applications [20][21][22]. ...
In this study, the compatibleness/effectiveness of the proposed novel semi-overlapping winding (NSW) topology has
been investigated by implementing into different synchronous machine technologies, namely interior permanent-magnet
machine, synchronous reluctance machine (SynRM), permanent-magnet assisted SynRM, and double-salient reluctance
machine. All considered machines have also been designed with different winding topologies; i.e. integer-slot distributed
winding, fractional-slot concentrated winding (FSCW) in order to reveal the merits/demerits of the proposed NSWs. A
comprehensive electromagnetic performance comparison has been presented. It has been validated that the proposed winding
topology promises significant advantages; such as improved efficiency with substantially reduced total axial length, low eddy
permanent magnet (PM) loss and low risk of irreversible magnet demagnetisation over conventional winding topologies. It has
also been revealed that the implementation of proposed NSWs into the reluctance machines results with higher torque and
power output than that of FSCWs.
... Among the available motor technologies, permanent magnet assisted synchronous reluctance motors (hereafter called PMaSyRMs) represent a flexible solution since it is possible to properly size the PMs to be inserted within the rotor slots so to reach a particular target: the widest constant power speed range or the maximum torque given the outer envelope. The design of this particular machine topology has been investigated by several authors in the last few decades, either adopting analytical approaches [12], [13] or FE aided optimizations [14], [15]. The approach presented in [12] is effective for design purpose as it allows to obtain a reasonable design for a given outer envelope, targeting a predefined performance index for the PM insertion, with a limited computational effort when compared to brute-force design optimizations. ...
Permanent magnet assisted synchronous reluctance motors are becoming a promising solution for electric vehicles, thanks to their high power density, efficiency and increased constant power speed range. The design of the rotor geometry, in terms of amount of PM to be inserted within the machine rotor slots, constitutes a challenging task which has to considered the requirements in terms of speed and torque during a typical electric vehicle driving cycle. This paper presents a comparison among different permanent magnet assisted synchronous reluctance motors for electric vehicles, by also investigating the influence of the number of pole pairs on the main performance indicators. The selected machines are therefore compared in terms of overall efficiency and operating limits, thus leading to some design insights for a given outer envelope.
... Heavy loss in an HPMSM will make it unable to drive the load and will threaten the safety of the system [6]. To obtain better performance from an HPMSM, developing its optimized construction has become a research hotspot [7]. the solution of them. ...
In this paper, a novel bat algorithm based on the quantum computing concept and pyramid neural network (PNN) is presented and applied to the electromagnetic motor optimization problem. Due to the problems of high loss, high temperature rise and threatening motor safety, it is necessary to optimize the design of high-speed permanent magnet synchronous motor (HPMSM) structure. In order to use less training data and avoid the problem of large computational costs due to repeated finite element simulation in the electromagnetic structure design, this paper adopted a performance-driven method to establish the PMSM model. This model could effectively reduce the dimensions of the parameter space and establish an effective high-quality model within a wide range of parameters. For the purpose of obtaining a reliable proxy model with less training data, this paper adopted a pyramid-shaped neural network, which could reduce the risk of overtraining and improve the utilization of specific problem knowledge embedded in the training data set. The quantum bat algorithm (QBA) was used to optimize the structure of the PMSM. Compared with the classical GA and PSO algorithms, the QBA has the characteristics of a rapid convergence speed, simple structure, strong searching ability and stronger local jumping mechanism. The correctness and effectiveness of the proposed PNN-based QBA method were verified using simulation analysis and a prototype test.
... Among these machines, PM brushless machines exhibit higher efficiency, simple control, robust structure, and high-power torque density; however, the fear of extinction and rapidly increasing prices of rare earth magnets make the PM machines a luxury for industrial as well as commercial applications [1][2][3]. Therefore, the researchers are taking more interest in the cheaper and alternative ways where less or no magnets are required, i.e., hybrid excitation synchronous machines and wound-rotor synchronous machines [4][5][6][7][8]. ...
This paper presents a topology for the brushless operation of a wound-rotor synchronous machine based on the subharmonic excitation technique by using two sets of multi-pole windings on the armature as well as on the rotor. The armature windings consist of a four-pole three-phase main winding and a two-pole single-phase additional winding, responsible for the generation of fundamental and subharmonic components of magnetomotive force (MMF), respectively. The rotor contains four-pole field winding and two-pole excitation winding. From the generated air gap MMF, the additional winding is responsible for induction in excitation winding, which feeds DC to the field winding through a rotating rectifier without the need of brushes. Then, the interaction of the magnetic field from the main and the field windings produces torque. The proposed topology is analyzed using 2D finite element analysis (FEM). From the analysis, the generation of the subharmonic component of MMF is verified, which helps in achieving the brushless operation of the wound-rotor synchronous machine. Furthermore, the performance of the proposed brushless multi-pole topology is compared with the existing dual three-phase winding multi-pole topology in terms of current due to induction, output torque, torque ripples, and efficiency.
... S a high torque density electromagnetic energy conversion device with low cost and simple structure, the permanent magnet (PM) motor is widely applied in various applications, while its performance is directly related to the performance of permanent magnets [1]- [2]. At present, the application of high-performance PMs such as NdFeB has significantly improved the efficiency and torque/power density of PM motor Manuscript [3]- [4]. However, as a non-renewable resource, NdFeB material is directly affected by market supply and resource reserves [5]- [6]. ...
Permanent magnet assisted synchronous reluctance motor (PMA-SynRM) is a kind of high torque density energy conversion device widely used in modern industry. In this paper, based on the basic topology of PMA-SynRM, a novel PMA-SynRM of asymmetric rotor with position-biased magnet is proposed. The asymmetric rotor design with position-biased magnet realizes the concentration of magnetic field lines in the motor air gap to obtain higher electromagnetic torque, and makes both of magnetic and reluctance torque obtain the peak value at the same current phase angle. The asymmetric rotor configuration is theoretically illustrated by space vector diagram, and the feasibility of high torque performance of the motor is verified. Through the finite element simulation, the effect of the side barrier on output torque and the Mises stress under the rotor asymmetrical design are analyzed. Then the motor characteristics including airgap flux density, back EMF, magnetic torque, reluctance torque, torque ripple, losses, and efficiency are calculated for both the basic and proposed PMA-SynRMs. The results show that the proposed PMA-SynRM has higher torque and efficiency than the basic topology. Moreover, the torque ripple of the proposed PMA-SynRM is reduced by the method with harmonic current injection, and the torque characteristics in the whole current cycle are analyzed. Finally, the endurance to avoid PM demagnetization is confirmed based on the PM remanence calculation.
... In the case of an X-EV traction motor, which has a wide range of operating speeds, current phase control is used to extend the operating speed range [5][6][7]. As the ratio of the d-axis current to line current for high-speed operation increases, the eddy current loss in the PMs tends to increase. ...
We designed and analyzed an interior permanent magnet synchronous motor (IPMSM) to prevent irreversible demagnetization of the permanent magnets (PMs). Irreversible demagnetization of NdFeB PMs mainly occurs due to high temperature, which should thus be minimized. Therefore, it is necessary to reduce the eddy current loss in the PM through optimal design. The shape of the rotor core was optimized using finite element analysis (FEA) and response surface methodology. Three-dimensional (3-D) FEA is required for accurate computation of the eddy current loss, but there is huge time, effort, and cost consumption. Therefore, a method is proposed for indirectly calculating the eddy current loss of PMs using 2-D FEA. A thermal equivalent circuit analysis was used to calculate the PM temperature of the optimized model. For the thermal analysis, the copper loss, core loss, and eddy current loss in PMs were estimated and applied as a heat source. Based on the results, we confirmed the stability of the optimum model in terms of the PM demagnetization.
... After this first stage, the effects of the PM insertion are evaluated with analytical or finite element tools. In particular, the PM quantity is dictated by the adopted design criterion, i.e. obtain either the widest constant power speed range or the maximum torque increment [9], [10] subject to the constraints imposed by the demagnetization phenomena [11]. The distribution of the PMs within the rotor flux barriers is instead selected so to reduce the harmonic content of the resulting airgap flux density and consequently the torque ripple. ...
The design of synchronous reluctance machines with and without permanent magnets assistance constitutes a challenging engineering task due to the numerous design variables and performance indexes to be considered. The design complexity increases even further when the application requires high speed operation, with consequent rotor structural constraints and and related effects on the electromagnetic performance. Structured as two-parts companion papers, this first part proposes a comprehensive design procedure able to consider all the non-linear aspects of the machine behaviour, greatly reducing the number of independent design variables, without worsening the computational burden. In particular, the non linear behaviour of the rotor iron ribs and the effect of the permanent magnets on the structural design are all taken into account with the proposed iterative design procedure targeting the achievement of a desired power factor. The proposed method will be then used to draw some preliminary design considerations highlighting the several trade-offs involved in the design of high speed permanent magnet assisted synchronous reluctance machine. Part I is setting the theoretical bricks that will be further expanded and experimentally validated in the companion paper Part II.
... The interior flux barriers are placed in the q-axis direction (L d > L q ). In order to increase the reluctance torque component, the rotor anisotropy is maximized by introducing more than one flux barrier [49]. This topology shares similar features with IPM in terms of constant power achieved during flux-weakening operation. ...
In the last decade, the trend toward higher efficiency and higher torque density electrical machines (EMs) without permanent magnets (PMs) for the industrial sector has rapidly increased. This work discusses the latest research and industrial advancements in synchronous reluctance machines (SynRMs), being the emergent motor topology gaining wide acceptance by many industries. This article presents an extensive literature review covering the background and evolvement of SynRM, including the most recent developments. Nowadays, SynRM has found its niche in the EM market, and the reasons for that are highlighted in this work together with its advantages and disadvantages. The key journal publications in SynRM topics are discussed presenting the biggest challenges and the latest advancements with particular regards to the design methodology. This article aims to provide a thorough overview to the research community and industry about SynRM. There is a clear potential for SynRM to take over a significant portion of the EM market in the near future to meet efficiency standards in industrial applications without the use of rare-Earth PM technology.
... Besides the radial flux topologies, recently a concept for an axial flux SynRM was proposed [7]. Finally, the last evolution step for further enhancing the capabilities of these type of machines was to insert permanent magnets in their rotor structure [8]. The motor produces the torque based on solely the reluctance principle, therefore in order to increase its torque/power density, the so-called saliency ratio, which is the ratio between the quadrature inductances (ξ = ⁄ ) has to be maximized. ...
In this paper a side-by-side comparison between synchronous reluctance machines (SynRMs) with concentrated and distributed windings is performed. The characteristics, parameters, and the installation space of a permanent magnet synchronous machine (PMSM) with concentrated windings used in a 13 V automotive cooling fan system (CFMs) are used as requirements and specifications. For that, eight SynRMs with different stator and rotor topologies are investigated and optimized by means of FE-based electromagnetic optimization. Knowing the challenges associated with the development of mechanically stable SynRM rotor structures, for two selected cross-sections in view of being prototyped, designs checks are performed to ensure robust operation at up to two times the required operating speed. The simulated results were verified by means of measurements performed using two different types of loading systems, i.e., with the real ventilator and using a DC machine as a load. Based on this, the relative differences between all three motor technologies in terms of important quantities (e.g., torque-speed characteristic, torque ripple, efficiency, power factor and ultimately the size) are highlighted.
... Adding ferrite PMs to the rotor, PMSynRM exploits the peculiar rotor characteristic of SynRM and the high performance of PMSM at the same time, as shown in Reference [63]. These motors have a desirable performance at higher speeds than base speed, fulfilling the constant-power speed range requirements [64,65]. The currents for the same torque are decreased in PMSynRM. ...
Recent studies show that synchronous reluctance motors (SynRMs) present promising technologies. As a result, research on trending SynRMs drive systems has expanded. This work disseminates the recent developments of design, modeling, and more specifically, control of these motors. Firstly, a brief study of the dominant motor technologies compared to SynRMs is carried out. Secondly, the most prominent motor control methods are studied and classified, which can come in handy for researchers and industries to opt for a proper control method for motor drive systems. Finally, the control strategies for different speed regions of SynRM are studied and the transitions between trajectories are analyzed.
... Nonetheless, there are some problems, such as the vibration and acoustic noise in SRMs [13][14][15], and low power factor in SynRMs [16][17][18][19]. Moreover, rare-earth PMs can be partially replaced by low-cost ferrite magnets [20][21][22][23][24][25][26][27][28][29][30][31][32]. Although the performance of electrical machines with ferrite magnets can be improved, there are still some shortcomings, such as low power factor and low torque density due to low remanence of ferrite magnets. ...
In this paper, a novel permanent magnet-assisted synchronous reluctance machine (PMASynRM) with rare-earth PMs and ferrite magnets is proposed. The performance of PMASynRM is discussed with respected to the different magnet ratio of rare-earth PMs and ferrite magnets. Some characteristics including the flux density, output torque, cogging torque, output power, power factor, torque ripple, loss, efficiency, and demagnetization are calculated by 2-D finite element analysis (FEA). The analysis results show that the excellent performance can be obtained by using hybrid magnet of rare-earth PMs and ferrite magnets with the suitable magnet ratio, and provide some desirable cost-performance trade-off.
... However, the limited supply and increasing price of permanent magnet (PM) material has significantly increased the cost of these machines [8] - [12]. Therefore, there is a need to search for alternatives to PMSMs that require a low volume of permanent magnets such as hybrid excited synchronous machines [13] - [16] or machines that do not require permanent magnets at all, such as wound rotor synchronous machines (WRSMs) [17]. In [18], different machine topologies including those of PMSMs, induction machines (IMs), and WRSMs have been studied for EV application. ...
This paper presents a novel dual-mode wound rotor synchronous machine (DWRSM) for variable speed applications. The proposed machine combines the advantages of both the conventional wound rotor synchronous machine (CWRSM) and the brushless wound rotor synchronous machine (BWRSM). Unlike the existing BWRSM, through the dual-mode operation of the proposed machine, constant torque is achieved in the constant torque region by operating the machine in mode-I, i.e., as a CWRSM, and constant power is achieved in the field weakening region by operating the machine in mode-II, i.e., as a BWRSM. The mode change is performed through an additional thyristor drive circuit. The airgap magnetomotive force (MMF) in both modes is derived analytically. To verify this principle, finite element analysis (FEA) and an experiment on a 1- horsepower prototype machine was performed, and key influential factors were verified. The transients in the stator currents and torque during the mode change was analyzed. The test results validated the correctness of the theory and the FEA results.
... With the improvement of permanent magnet (PM) performance and development of manufacture techniques, the PM machines have attracted increasing attention in academia and industry, offering the merits such as higher power density, toque density and efficiency [1] [2]. ...
The field winding based flux adjustable permanent magnet (FWFAPM) machines, including the hybrid excitation topology and the memory topology, can offer excellent capabilities in terms of flux regulation, wide constant power operation as well as de-excitation (flux-weakening) under fault, thus, they are capable for using in More Electric Aircraft (MEA) generator systems. First, this paper probes four basic hybrid excitation modes, and based on that, a general method deriving PM machines to hybrid excitation machines is established. The basic characteristics of each hybrid excitation mode considering the relationship between S-pole and N-pole are obtained for the first time. The performance differences of each hybrid excitation mode combined with different PM machines are summarized. Then, this general topology derivation method are extended for the memory topology, The unified derivation method of the single-PM topologies, the double-PM topologies and the triple-PM topologies for memory machines is systematically established.The general laws of the electromagnetic performance of each double-PM mode and triple-PM mode considering different relationships between NdFeB and AlNiCo are summarized for the first time. Finally, the control strategies for voltage regulation of aircraft generator systems are discussed based on the different critical control variables and controller types, a torque impulse balance control method which shows excellent dynamic performance for both target control variable and critical control variable has been achieved experimentally.
... The PMA-SynRM design and control have been proposed in several publications. Most of the research focused on the rotor's geometry based on machine design and optimization aspects [6][7][8][9][10] as well as the PM element [11][12][13]. Potential control methodology has been discussed in recent literature [14]. ...
It is necessary to find the suitable d - and q -axis reference currents to control PMA-SynRM motors with high efficiency. This paper presents the maximum torque per ampere (MTPA) to minimize the copper losses of the system and utilizes the field weakening control to operate above the rated speed of the PMA-SynRM. The copper losses equation and electromagnetic torque are used to optimize the d - and q -axis current references. A small-scale 1 kW prototype PMA-SynRM was designed and manufactured to test and examine the proposed control in the laboratory. The proposed algorithm was digitally carried out using the MicroLab Box dSPACE. The simulation results show that the copper losses of the machine with the MTPA algorithm are lower than those without the MTPA algorithm. The PMA-SynRM operates above the base speed of ~ 70 % in the constant power region by mean of field weakening control.
... In recent decades, many research works on PMSynRM are carried out in traction applications [3]. This machine has a desirable performance at high speeds, fulfilling the constant-power speed range requirements [16]. In addition, the usage of ferrite PMs has provided a reliable and low-cost choice for manufacturers. ...
Since the dominant induction machines and permanent magnet synchronous machines are well-established in the industry, the reluctance machines require more research work and investigation to substitute the conventional technologies. This paper analyzes the synchronous reluctance machines and permanent magnet-assisted synchronous reluctance machines in terms of the effect of permanent magnets in the model and the performance characteristic of the machines. The machines are designed and the parameters are measured. The vector diagrams of the machines and the equivalent circuits of the machines are analyzed. A comparison of the machines in terms of power factor, efficiency, and torque of the machines is provided based on the measurements. The study presents a notable improvement in power factor and efficiency in the case of inserting permanent magnets in the synchronous reluctance machine's rotor.
... The required load torque is determined by the gearbox specification. The motor speed response can be analyzed to calculate the average speed under load torque profile in each system by the integration of the BLAC vector control system [22], [23], as shown in Fig. 8. A 2D FEM is also used to analyze the motor control parameters, such as flux linkage and inductance, considering the nonlinear magnetic saturation characteristics of the core. ...
During motor production processes, the influence of motor manufacturing tooling costs on motor prices is mostly negligible and considered to be insignificant. The manufacturing cost, particularly the molding cost, may not be a significant issue for mass production, but it would become a crucial issue for modern small-scale application-oriented design. When the total number of motors produced per motor manufacturing tool such as stator and rotor pressing tool is reduced, the effect of the motor manufacturing tool cost on the motor price can be greatly increased. To reduce the cost, we present a new design approach of a brushless AC (BLAC) motor that shares motor manufacturing tools, unlike many previous studies on low-cost designs. The design approach of a BLAC motor is applied to integrated electric brake (IEB) systems of various specifications. In addition, to analyze the motor performances in IEB systems, the BLAC vector control system, FEM, design of experiment, and moving least square method are used. Furthermore, to predict the available operating time of a motor, a heat compensation coefficient that uses the experimental data of an existing motor is proposed. By implementing this design approach, we have effectively designed motors that satisfy performance requirements such as speed response, available operating time, and total harmonics distortion (THD) of back EMF with minimum stator core volume, in the IEB systems, and achieve a 25.5% reduction in cost through sharing of motor manufacturing tools.
Permanent magnet assisted reluctance (PMAREL) machine possesses a promising application prospect in the aircraft starter/generator (S/G) system. This paper presents a high-performance generation control strategy for a dual-three-phase (DTP) PMAREL S/G system. By studying the DTP machine models in the synchronous frame, a generation control framework suited for the DTP PMAREL machine is provided, which consists of a current-control inner loop and a voltage-control outer loop. For the current control, the negative effects of the magnetic saturation on the conventional current-control method are studied. To eliminate the negative effects of the magnetic saturation and to achieve good high-speed control performance, an improved flux-loop-based internal-model-control (IMC) current-control method is proposed. The performance and robustness of the proposed method are analyzed. For the voltage control, the load power feedforward technique is adopted to improve the dynamic performance of the generation control. Based on a prototype of DTP PMAREL S/G system, experiments are conducted and the results verify the correctness of the analysis and the effectiveness of the proposed method.
In this paper, a driving cycle design optimization approach using the dimension reduction method is proposed for a less-rare-earth permanent magnet (LRE-PM) motor. In order to improve the efficiency of driving cycle optimization, the k-means clustering method, sensitivity analysis, and principal component analysis are utilized to reduce the dimensions of operating points, design parameters, and optimization objectives respectively. Furthermore, based on multi-objective genetic algorithm, improved motor performances of the whole driving cycle can be realized, including relatively high output torque, low torque ripple, low motor loss, and high demagnetization withstand capability. In addition, motor performances over the driving cycle before and after optimization are compared in detail. Finally, a prototype motor is built and tested. Both simulation and experimental results indicate that motor performances can be improved efficiently and comprehensively, which provides a potential research path for high-efficiency driving cycle optimization.
Due to the trade-off between rotor mechanical strength and magnetic leakage, the high-speed capability of interior permanent magnet machines (IPMSM) is severely limited. This paper proposes a novel rotor topology capable of delivering 5 kW at 100,000 rpm using commercialized electrical steel laminations. By implementing the mechanical analysis in an iterative evolution process, two promising new topologies were developed. The first topology uses smooth compound curves (CC) to minimize the stress concentration and will be referred to as CC-type; the second topology is developed based on the CC-type with the aim to strengthen the structure further using the concept of a double-tied arch bridge (DAB) and referred as the DAB-type henceforward. After comparing the designs obtained from a detailed multiphysics optimization process, the DAB-type design was found to outperform the CC-type in all aspects, especially the mechanical robustness. This design was selected for experimental verification and a prototype was constructed. The mechanical and electromagnetic performances of the design were fully verified experimentally. The DAB-type prototype has achieved 2.31×10
<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup>
rpm√kW, which is 1.5 times higher than other laminated rotor high-speed IPMSM designs found in the literature.
Currently, electric automobiles are predominantly powered by interior permanent magnet electric machines which possess high efficiency and torque density in comparison to alternative machine types. Although the performance benefits are undisputed, the use of rare earth permanent magnet materials has historically been a commercial risk. To mitigate the potential issues, the automotive industry is considering alternative electric machine designs, which will either use none or a minimal amount of rare earth material.
In parallel, synchronous reluctance machines are "magnet-free" electric machine type currently the focus of process industry. Electric power take-off was selected as the application niche for the introduction of synchronous reluctance machine to the automotive sector. The goals of the thesis are to improve the synchronous reluctance machine optimization process by reducing rotor radial cross-section parametric complexity, and to create a software framework for the rotor geometry feasibility validation.
The research concentrates on a novel approach of defining rotor geometry on a shape object level, instead of the classical approach which uses geometrical primitives like points, lines, and arcs. This methodology allows simple and robust feasibility validation and robust calculation of at least one point inside every object, which is extremely important for assigning the material to different regions in the finite element analysis tool. The presented solution can be applied on any electric machine type.
Furthermore, the thesis defines a set of absolutely feasible synchronous reluctance machine rotor geometries using a minimal set of parameters in order to reduce design complexity. Consequently causing a reduction of overall optimization time due to the smaller number of parameters that define the optimization problem.
After selecting the geometry and commencing optimization, the optimization system (software code) must be able to detect if generated geometry is unfeasible (e.g., rotor barriers are overlapping). One of the proposed solutions is a novel concept of forced feasibility, where every unfeasible design is forced to change parameters until reaching feasibility. Otherwise, the infeasible candidate is rejected, which can affect the optimization convergence. Both approaches were compared concluding that forced feasibly causes faster optimization convergence.
Synchronous reluctance (Syn-Rel) machines with embedded permanent magnets (PMs) are research hotspots in variable speed motor drives due to their robust rotor structure and wide constant power speed range (CPSR). In this paper, the potential of PM-assisted Syn-Rel machine to be next generation heavy duty traction motor solution has been investigated, with special attention put on one key geometric parameter, i.e., airgap length. Careful machine design and optimization has been conducted based on geometric parametrization including airgap length variation, for 15000rpm peak speed and 350kW peak power output. In low speed operations, the influence of airgap length on different torque components has been analyzed in detail based on the frozen permeability method. In field weakening region, the variation trend of several key parameters such as output power, torque ripple, and power losses have been investigated along with airgap length. It is found that with high electric and magnetic loading, reducing the electromagnetic airgap length is not always beneficial. There exists a suitable airgap length value to comprehensively balance torque/power density, cooling capability, efficiency and reliability. Numerical FEA and experimental tests of the prototype are combined to verify the conclusions.
Permanent magnet assisted reluctance (PMAREL) machine possesses the potential as the aircraft starter/generator (S/G) for its high power density, high efficiency and tolerance to short-circuit faults. For aircraft S/G systems, the voltage build-up is a prerequisite for power generation. However, the voltage build-up of the PMAREL S/G system may fail if the initial DC-link voltage is low and the control is fast-response. In this paper, the mechanism of the voltage build-up failure is clarified. The conduction feature of power devices in the power electronic converter when the DC-link voltage is clamped at 0 V are explored. Conditions for clamping the DC-link voltage at 0 V all the time is determined. An integrated control method is proposed to cope with the voltage build-up failure as well as improve the dynamic performance of the S/G system. Based on a prototype of PMAREL S/G system, the correctness of the analysis and the effectiveness of the proposed method are verified through experiments.
According to air-gap field-modulation theory, multiple field harmonics are responsible for high torque density of field modulation (FM) motors. However, abundant field harmonics will undoubtedly increase motor losses, especially iron loss and PM eddy-current loss. Therefore, a harmonic-analysis-based loss minimization (HLM) method incorporated into model predictive torque control (MPTC) for efficiency improvement of FM motors is proposed in this paper. First, by analyzing the loss generation mechanism, a harmonic-based online loss calculation model is built to serve for loss minimization control. Then, the reference flux for MPTC can be derived from the proposed HLM method, which avoids complexity of equivalent resistance tuning and improves accuracy of loss calculation compared to the conventional model-based loss minimization method which lacks attention on the harmonic-based loss analysis. Consequently, the HLM-MPTC strategy is finally determined and then applied in a flux-concentrating field-modulation permanent-magnet (FCFMPM) prototype to verify its validity. The experimental results evidence that the proposed HLM-MPTC can effectively achieve loss reduction and efficiency improvement.
This paper deals with the finite element analysis of Hybrid Excitation Permanent Magnet Synchronous Motors, that is, synchronous motors characterised by a rotor including both permanent magnets and an excitation winding. Such a winding is adopted to modulate the rotor flux so that the motor exploits the maximum torque for any operating speed. The higher benefit is obtained at speeds higher than the nominal speed, i.e. during the flux weakening operations. Thus the focus is to determine the performance of different topologies of hybrid excitation PM synchronous motors, considering compared to those achieved with a standard interior PM synchronous motors. The possibility to vary the rotor flux in the hybrid excitation PM motors allows to design the motor with a high no-load flux linkage, necessary to get high torque at low speeds, and to get high torque in a wide speed range.
This article proposes a novel dual-three-phase high-power high-speed permanent magnet assisted synchronous reluctance starter generator (PMaSynR SG) for aviation application, which has the characteristics of high efficiency, high power density, high reliability, and excellent antishort-circuit ability. The proposed PMaSynR SG can obtain higher efficiency and power density by embedding permanent magnet in the rotor topology compared with the synchronous reluctance generator, and has better antishort-circuit ability compared with the permanent magnet synchronous starter-generator. Moreover, design of dual-three-phase winding is adopted, which not only reduces the phase current, but also improves the reliability. In this article, the topological structure, characteristics and principle of PMaSynR SG are systematically studied at first. Second, a simplified
dq
-axis equivalent magnetic circuit model is established, and the expressions of
dq
-axis inductance and permanent magnet flux linkage are derived on the basis of the basic parameter selection. Then, combined with parameter sensitivity analysis, the influence law of rotor structural parameters on antishort-circuit ability and electromagnetic performance is revealed. Finally, a 40 kW 24 000 r/min PMaSynR SG is designed and manufactured. The simulation and experimental results show that the proposed PMaSynR SG has excellent electromagnetic performance with the power density of 3.1 kW/kg and the efficiency of 94%, while the short-circuit current is only 59% of its rated value.
In this study, it is aimed to design an external rotor permanent magnet synchronous reluctance motor (PMSynRM) for an electric vehicle (EV). In recent years, developments in EV technology have increased the need for electric motor design. Electric motors designed to be used in EVs are considered to have high efficiency, high torque and high power density in a wide speed range. Considering these situations, one of the recently designed electric motors is the synchronous reluctance motor (SynRM). However, the disadvantage of a synchronous reluctance motor is the torque ripple. In this study, a 2-kW, three-phase, eight-pole, 24-slots hub motor with an external rotor (PM-SynRM) with a rotational speed of 750 rpm is designed. The design was modeled using the finite element method (FEM) and the necessary analysis was performed. When designing the flux barrier Ld/Lq rate was considered. By using permanent magnets in the design of electric motors, torque and efficiency values have been increased. For this reason, in our PMSynRM design, Neodymium Iron Boron (NdFeB) permanent magnet material is placed in the rotor flux barriers to increase torque. In addition, it is aimed to reduce the torque ripples at low speeds by selecting the distributed winding in the stator windings. Simulation results show that high torque is obtained with low torque ripple. In addition, good results were obtained in terms of efficiency, current, speed and power density.
This paper proposes an analytical method for the selection of the machine parameters and inverters power ratings of a synchronous motor operated in Open-End Winding (OEW) configuration with one of the two Voltage Source Inverters (VSIs) connected to a floating capacitor (FC) in order to meet a specific torque-speed profile. With the derived normalized expressions and curves all the suitable synchronous motors operated with an OEW-FC and a standard 2L-VSI drive can be easily compared according to the power rating and desired speed-torque characteristic.
With the growing demand for interior design solutions that are friendly to the green environment, there is a growing awareness of interior designers around the world to the sustainability strategy. Most of the traditional interior design and construction process consumes many natural resources in the manufacturing and installation process. This will harm the environment. Interior designers adopted a sustainable design technology, the opportunity to improve the healthy indoor air quality. To achieve sustainable solutions, materials, construction methods, furniture by selecting the lighting design options. Despite much sustainable design research, discussion of the interior design of sustainability criteria there little. Essential for sustainable standard interior design solutions to support the responsible interior designer. Therefore, this study aims to propose a set of criteria for selecting based on sustainable indoor network processors and embedded system design solutions to ensure a sustainable and consistent product mix of 3DWeb representation of interior design solutions thing. Finally, to enhance its functionality, come to an end because of the importance of effective standards.
Embedded applications like electric and hybrid vehicles are increasingly using electrical machines with a very high power / mass ratio. In this context, the design of such machines, very often operating at high speeds, becomes essential. However, in order to remain economically attractive, these machines cannot use rare earth magnets but at best include (low cost) ferrites. In this context, a significant number of publications have shown that reluctance synchronous reluctance machine (SynRM) may be a good choice. However, this type of machine gives poor performances due to the difficulty to get high saliency ratio. This saliency ratio may be improved by the use of low cost ferrites. The determination of the height of the magnetic bridges becomes then a problem of the prime importance to ensure both high-speed integrity and high saliency ratio. This paper proposes a fast model based on the Beam Theory Method (BTM) which is intended to be integrated in an electromechanical optimization process. This method will be compared to another one that has been previously introduced for this type of problem: the Equivalent Ring Method. The maximum mechanical stress at critical regions of the rotor of the assisted synchronous reluctance machine can then be calculated for different rotating speeds and rotor iron bridge thicknesses. By adopting the concept of stress concentration, both methods are compared with the results of finite element analyses. Finally, a prototype of the assisted synchronous reluctance machine is used to validate these results from finite element simulations.
While electric vehicle (EV) technology has been established in passenger vehicle sector, commercial multipurpose vehicle (MPV) penetration is strictly related to the niche end-markets, like medium-duty, short-haul and last mile applications. Some of the examples of short-haul applications are electric multipurpose vehicles (eMPV) like refuse, hook-loader or vacuum trucks. eMPVs, apart from electric traction, have to actuate additional body systems by the means of electric power takeoff (ePTO). Taking into consideration that the machine needs to be affordable and reliable, synchronous reluctance machine (SyRM) has been selected for ePTO actuation. This paper will present SyRM parametrization, design constraints and optimization via improved differential evolution (DE) algorithm .
In this article, a new controllable leakage flux multilayer barrier permanent magnet (PM) motor is proposed by adopting a new design concept of controllable leakage flux, where the PMs are uniquely placed in the
d
-axis magnetic circuit of the synchronous reluctance motor (SynRM). Compared to the conventional
q
-axis PM placement SynRM, the higher PM utilization and better flux-weakening capability can be obtained. For further comparison and verification, both of the controllable leakage flux multilayer barrier PM motor and the motor with traditional
q
-axis PM setting are designed. In addition, a multiobjective optimization method based on the correlation analysis method is proposed to obtain the optimized output torque and flux-weakening performances. Then, the performances of the two optimal motors are analyzed and compared in detail. Finally, two prototype motors are manufactured and tested. Both the theoretical and experimental analyses verify the effectiveness of the flux-weakening enhancement design and the proposed motor.
In this paper, a novel High Power Density Permanent Magnet Synchronous Machine (HPDPMSM) is proposed. The flux-weakening ability and efficiency at high speed are improved by the proposed bypass-ribs added in the flux barriers. The working principle of the bypass-rib is analyzed and the effects of main parameters of the bypass-rib on the characteristics are investigated. The performances of the proposed HPDPMSM are analyzed and compared with that of the HPDPMSM without bypass-rib on 2D finite-element analysis (FEA), including the cogging torque, output torque, constant-power speed range, losses and efficiency. The results show that both HPDPMSMs generate comparable output torque and have the same maximum output power, while the proposed HPDPMSM has lower torque ripple, wider constant-power operation range and higher efficiency in the flux weakening operation region.
A predictive torque and flux control algorithm for the synchronous reluctance machine is presented in this paper. The algorithm realizes a voltage space phasor pre-selection, followed by the computation of the switching instants for the optimum switching space phasors, with the advantages of inherently constant switching frequency and time equidistant implementation on a DSP based system. The criteria how to choose the appropriate voltage space phasor depend on the state of the machine and the deviations of torque and flux at the end of the cycle. In order to obtain an appropriate model of the machine, it has been developed on a d-q frame of coordinates attached to the rotor and takes into account the magnetic saturation in both d-q axes and the cross saturation between both axes. Therefore, the torque dynamic is improved and its ripple is reduced. Simulated and experimental results using a DSP and a commercially available machine show the validity of the proposed control scheme.
This paper deals with the flux-weakening control of surface-mounted permanent-magnet synchronous motors, taking into account the influence of the resistive voltage drop in the stator windings, whose effect is usually neglected in similar studies. First, the motor equations exploiting the optimal torque-speed limits in the flux-weakening region are evaluated and discussed. Then, the influence of the resistive voltage drop is pointed out, highlighting its effect on the setup of the flux-weakening strategy. Hence, a simplified approach to flux-weakening motor control is presented, useful for the practical implementation in microcontrolled drives. Finally, experimental results are shown, using a position tracking application as a test case.
Synchronous machines that are optimally designed using finite-element (FE) software, and control of such machines using powerful digital signal processors (DSPs), are commonplace today. With field-orientated control, the maximum-torque-per-ampere control strategy for unsaturated voltage conditions (below the base speed) is well known; the field-weakening strategy, however, could be rather complicated. In this paper, a straightforward torque control strategy for the entire speed range is proposed and demonstrated. Practical implementation of the method is very simple since the calculations are done offline in an automated process and are therefore removed from the load of the DSP. The process relies on machine-specific data from FE analysis and therefore includes nonlinear effects such as saturation and cross coupling. Simulation and practical results for a permanent-magnet and a reluctance synchronous machine show that the torque is controlled effectively in the entire speed range using this generic method.
Software organizations have increased their interest on software process improvement (SPI). In high maturity levels, SPI involves implementing statistical process control (SPC), which requires measures and data that are suitable for this context. However, this has been pointed in the literature as one of the main obstacles for a successful implementation of SPC in SPI efforts. This paper presents an instrument for evaluating the suitability of measurement repositories in order to support software organizations implementing SPC.
With ever-increasing concerns on our environment, there is a fast growing interest in electric vehicles (EVs) and hybrid EVs (HEVs) from automakers, governments, and customers. As electric drives are the core of both EVs and HEVs, it is a pressing need for researchers to develop advanced electric-drive systems. In this paper, an overview of permanent-magnet (PM) brushless (BL) drives for EVs and HEVs is presented, with emphasis on machine topologies, drive operations, and control strategies. Then, three major research directions of the PM BL drive systems are elaborated, namely, the magnetic-geared outer-rotor PM BL drive system, the PM BL integrated starter-generator system, and the PM BL electric variable-transmission system.
Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.
This paper proposes a novel speed-sensorless direct torque and flux control scheme for an interior permanent-magnet synchronous motor drive. The drive uses a new stator flux observer based on the extended rotor flux concept. Due to the simultaneous implementation of stationary and rotating reference frames, the proposed observer does not require any speed adaptation and is inherently sensorless. Unlike speed adaptive observers, the proposed observer is immune to speed estimation errors; thus, its performance at very low speed is improved significantly. A novel stator resistance estimator is incorporated into the sensorless drive to compensate the effects of stator resistance variation. The global asymptotic stabilities of both the flux observer and stator resistance estimator are guaranteed by the Lyapunov stability analysis. Simulation and experimental results at very low speeds, including 0 and 5 r/min, confirm the effectiveness of the proposed method.
Permanent-magnet (PM) machines are considered the most suitable machine type for very high speed applications. Still, due to the growing demand for the ever higher rotational speeds, PM machines are approaching their limits. The focus of this paper is the different factors that lie behind the inherent speed limitations of PM machines. The limits-thermal, elastic, and rotor dynamical-are defined, classified, and correlated to basic machine parameters.
This paper describes an enhanced optimal-torque-control strategy for fault-tolerant permanent-magnet (PM) machines under flux-weakening operations. By adjusting the degree of flux weakening according to estimated instantaneous-torque-control errors, the torque-control performance of the machine can be improved when operating above its base speed under either open- or short-circuit fault condition. Extensive simulations under both healthy and fault conditions have been undertaken in order to validate the effectiveness of the proposed control strategy. Experimental results have also been given based on the testing of a prototype five-phase fault-tolerant PM machine.
This paper theoretically introduces and develops a new operation diagram (OPD) and parameter estimator for the synchronous reluctance machine (SynRM). The OPD demonstrates the behavior of the machine's main performance parameters, such as torque, current, voltage, frequency, flux, power factor (PF), and current angle, all in one graph. This diagram can easily be used to describe different control strategies, possible operating conditions, both below- and above-rated speeds, etc. The saturation effect is also discussed with this diagram by finite-element-method calculations. A prototype high-performance SynRM is designed for experimental studies, and then, both machines' [corresponding induction machine (IM)] performances at similar loading and operation conditions are tested, measured, and compared to demonstrate the potential of SynRM. The laboratory measurements (on a standard 15-kW Eff1 IM and its counterpart SynRM) show that SynRM has higher efficiency, torque density, and inverter rating and lower rotor temperature and PF in comparison to IM at the same winding-temperature-rise condition. The measurements show that the torque capability of SynRM closely follows that of IM.
In this paper, we develop novel rotor designs of interior-permanent-magnet motors in order to reduce harmonic iron losses at high rotational speeds under field-weakening control. First, an optimization method, combined with an adaptive finite-element method, is applied to automatically determine the shapes of the magnets and rotor core. The optimized motor is manufactured to confirm the validity of the calculation. It is clarified that the iron loss of the optimized motor is reduced to nearly half of that of the conventional motor, without a significant decrease in maximum torque. Next, the contribution of each part of the rotor to the iron-loss reduction is analyzed by the experimental design method. Finally, several designs of the rotors are proposed from the viewpoints of manufacturing cost and performance.
The interior permanent magnet (IPM) synchronous motor is characterized by a high rotor anisotropy. Such an anisotropy is the cause of a high harmonic content of the air gap flux density distribution, almost independent of the main flux. As a consequence there are fluctuations of the flux density in the stator iron, and consequently eddy current iron losses. This aspect is prominently evident during flux-weakening operations, when the armature current weaken the PM flux and the motor runs above base speed. This paper presents a complete study of such a phenomenon, including an analytical model, a finite element validation, as well as an experimental confirmation of the predicted results. Finally, some suggestions are given in order to design an IPM motor exhibiting reduced iron losses during all operating conditions.
Modern interior permanent magnet motors, suited to large constant-power speed ranges, have a multiple flux-barrier rotor structure and show a quite complex magnetic behavior. In this paper, the flux-current relationship of such motors is analyzed, and a simplified but effective model of the cross-saturation phenomenon is proposed and verified by experiment. In addition, new flux variables are introduced that allow a rigorous splitting of permanent-magnet (PM) and reluctance torques. It is shown that the PM contribution to torque is larger than expected from the PM no-load flux. This can lead to more accurate machine design and control strategies.
The design optimization of IPM motors for wide speed ranges is pursued by means of a FEA-based multi-objective genetic algorithm (MOGA). Respect to previous works in the literature, the proposed approach evaluates the motor performance with a very limited number of simulations, making FEA optimization more attractive. The 3 goal functions (motor torque, torque ripple and flux weakening capability) are evaluated by means of 7 static FEA runs, that means nearly 20 seconds per tentative motor with a laptop computer. The paper is focused on the rotor design, since it is the most controversial part of IPM design and the most difficult to be modeled due to magnetic saturation. Three different approaches are presented: a fast one, based on 2- objective optimization, a hybrid one, based on 2-objective optimization and 3-objective refinement, and actual 3-objective optimization. The results presented here will be the base for future, more comprehensive optimization.
Interior permanent magnet (IPM) synchronous machines result to be a valid motor topology in case of both high efficiency and high flux-weakening range. In industry applications the design of interior permanent magnet (IPM) synchronous machines requires to satisfy an increasingly number of limitations. For an IPM machine the key parameters that can be used for a performance maximization refer to many aspects: geometry, material property, cost, control strategy. According to the size and geometry limitations of an IPM motor for a very high flux-weakening speed range is required, the paper analyzes how to maximize the performance modifying the PM quantity. FE simulations, are firstly verified comparing the results with measurements on a prototype, and then they are used to evaluate the tradeoffs of the different cases.
The interior permanent-magnet (IPM) synchronous motor is characterized by a high rotor anisotropy. Such an anisotropy is the cause of a high harmonic content of the air-gap flux density distribution, almost independent of the main flux. As a consequence, there are fluctuations of the flux density in the stator iron and, consequently, eddy-current iron losses. This aspect is prominently evident during flux-weakening operations, when the armature current weakens the permanent magnet flux and the motor runs above the base speed. This paper presents a complete study of such a phenomenon, including an analytical model and a finite element validation, as well as an experimental confirmation of the predicted stator tooth flux waveforms. Finally, some suggestions are given in order to design an IPM motor exhibiting reduced iron losses during all operating conditions.
Interior permanent magnet (IPM) synchronous machines can experience large harmonic eddy-current losses in the stator teeth under flux-weakening operation, significantly depressing the efficiency of these machines at high operating speeds. This paper presents a new analytical/finite-element hybrid design approach to reduce the harmonic eddy-current losses in IPM machine stator teeth during flux-weakening operation. The proposed technique achieves this objective by three steps: 1) developing an analytical index for the harmonic eddy-current losses in IPM machine stator teeth; 2) designing the spatial distribution of the rotor MMF to minimize the analytical index; and 3) synthesizing the rotor geometry to implement the desired rotor MMF function while maintaining the basic machine characteristics unchanged. It will be shown that two-layer rotors, if properly optimized, are significantly more effective than one-layer rotors for the purpose of reducing the harmonic eddy-current losses in IPM machine stator teeth during flux-weakening operation at high speeds.
This paper focuses on the benefits of adaptive control for permanent-magnet synchronous machines; a novel method of online parameter estimation for such machines has been developed. Two recursive least square algorithm segments, a fast and a slow one, are uniquely combined in real time with rich enough data from the machine to estimate all four machine parameters instead of a subset of these. Simulation and experimental results demonstrate the effectiveness of the proposed method.
A design approach oriented to minimization of torque-ripple is
presented, for synchronous reluctance motors of the transverse-laminated
type. First, the possible types of rotors are classified and the more
suited rotor structure is evidenced, to be matched to a given stator.
Then, the inner rotor design is described, pointing-out the low-ripple
measures. Last, experimental results are given, from three different
rotors: they confirm the validity of the proposed approach
A constant-parameter equivalent-circuit model which neglects motor
losses is used to determine the effects of d - q
reactances and open-circuit voltage on the power capability of salient
pole permanent magnet motors in variable-speed-drive applications. It is
shown that peak power capability over a range of speeds can be obtained
by proper control of the armature current magnitude and phase. Due to
the voltage constraint imposed at the motor terminals, the power
capability will fall to zero for most motor designs at a given high
speed. A simple relationship between the motor open-circuit voltage and
the direct axis reactance is derived to obtain motor designs that, even
with this voltage constraint in place, extend their theoretical power
capability, neglecting losses, to infinite speed. All results are
presented in normalized curves using a per-unit system
The paper examines the theoretical and practical limitations to
the field-weakening performance of surface permanent magnet, synchronous
reluctance and interior permanent magnet motors when driven from an
inverter with a limited volt-ampere rating. It is shown that the
`optimal' field-weakening performance consists of an infinite
constant-power speed range but is limited to an inverter utilisation of
about 0.7. The new concept of the interior permanent magnet parameter
plane is introduced. This graphically illustrates the effect of varying
the drive parameters on the shape of the field-weakening characteristic.
The interior permanent magnet parameter plane is used to show that there
are three types of optimal field-weakening designs. When practical
factors and considerations are taken into account, the optimal
high-saliency interior permanent magnet motor design is the most
promising for applications requiring a wide field-weakening range. A 7.5
kW design was built and a constant-power speed range exceeding 7.5:1 was
demonstrated
This paper deals with the selection of the motor parameters and
the inverter power ratings for a permanent magnet (PM) synchronous motor
drive in order to meet a given flux-weakening torque versus speed
characteristic. Appropriate combinations of stator PM flux linkage, d-
and q-axis inductances, and inverter current rating at a given voltage
are derived, in normalized values, as functions of the specified
flux-weakening speed range and torque limits. By means of these sets of
data, the drive designer can easily individuate and compare all the
suitable synchronous motors (defined by the d- and q-axis inductances
and flux linkage) and the related inverter volt-ampere ratings, for the
desired flux-weakening performance. Therefore, this paper can be
considered a synthesis work rather than an analysis one and can
profitably be used for an optimal design of a synchronous motor drive
This paper presents design and analysis results of a 2.6-kW interior permanent-magnet synchronous motor developed for an electrohydraulic power steering system. The motor was designed by using the proposed equivalent magnetic circuit model in consideration with a core loss. To analyze motor characteristics by using the equivalent magnetic circuit model, inductance and iron-loss resistance, which are affected critically by magnetic saturation, are obtained by using finite-element analysis. Finally, motor characteristics such as armature current, torque, and efficiency are calculated by the equivalent magnetic circuit model and verified by experimental results.
In this paper, we propose a systematic optimization approach to flux-weakening control of interior permanent-magnet (IPM) motors, which operate in magnetic saturation. The current commands are chosen to be optimal so as to minimize power loss not only in the constant-torque region but also in the constant-power region. Our approach aims at the same objective as the previously known flux-weakening control. Furthermore, the motor torque of an IPM motor in magnetic saturation can be made exactly linear with respect to the torque command. Thereby, our systematic approach can provide not only maximal power efficiency but also torque linearity. In doing so, we consider a more general situation than that considered in prior literature. Specifically speaking, the physical constraints in stator currents and voltages, and the effect of stator resistance are all taken into full account. As a result, the optimization problem becomes very complicated. Nonetheless, we have successfully found the approximate optimal solution, which can be readily implemented on a usual high-speed microprocessor. The practical effectiveness of the proposed control method is also demonstrated through various simulation and experimental results.
A predictive torque and flux control algorithm for the synchronous reluctance machine is presented in this paper. The algorithm realizes a voltage space phasor preselection, followed by the computation of the switching instants for the optimum switching space phasor, with the advantages of inherently constant switching frequency and time equidistant implementation on a DSP-based system. The criteria on how to choose the appropriate voltage space phasor depend on the state of the machine and the deviations of torque and flux at the end of the cycle. In order to obtain an appropriate model of the machine, it has been developed on a d-q frame of coordinates attached to the rotor and takes into account the magnetic saturation in both d-q axes and the cross-saturation phenomenon between both axes. Therefore, high-performance torque control is achieved, and the torque ripple is reduced. Simulated and experimental results using a DSP/field-programmable-gate-array-based control and a commercially available machine show the validity of the proposed control scheme
Permanent magnet AC (PMAC) motor drives are finding expanded use
in high-performance applications where torque smoothness is essential.
This paper reviews a wide range of motor- and controller-based design
techniques that have been described in the literature for minimizing the
generation of cogging and ripple torques in both sinusoidal and
trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the
greatest potential for pulsating torque minimization using well-known
motor design techniques such as skewing and fractional slot pitch
windings. In contrast, trapezoidal PMAC drives pose more difficult
trade-offs in both the motor and controller design which may require
compromises in drive simplicity: and cost to improve torque smoothness.
Controller-based techniques for minimizing pulsating torque typically
involve the use of active cancellation algorithms which depend on either
accurate tuning or adaptive control schemes for effectiveness. In the
end, successful suppression of pulsating torque ultimately relies on an
orchestrated systems approach to all aspects of the PMAC machine and
controller design which often requires a carefully selected combination
of minimization techniques
The interior permanent magnet (IPM) synchronous motor is compatible with extended-speed-range constant-power operation by means of flux-weakening control. Flux weakening uses stator current components to counter the fixed-amplitude magnetic airgap flux generated by the rotor magnets, performing a role similar to field weakening in a separately excited dc motor. The nature of current regulator saturation caused by the finite inverter dc source voltage is described, marked by premature torque and power degradation at high speeds in the absence of flux-weakening control. This is followed by presentation of a new flux-weakening control algorithm developed as a modification of an established feedforward IPM torque control algorithm described previously in the literature. Attractive features of this new algorithm include smooth drive transitions into and out of the flux-weakening mode, fast response, as well as automatic adjustment to changes in the dc source voltage. Simulation and empirical test results from a 3-hp laboratory IPM motor drive are used to confirm the constant-power operating envelope achieved using the new flux-weakening control algorithm.
Interior permanent-magnet (IPM) synchronous motors possess special features for adjustable-speed operation which distinguish them from other classes of ac machines. They are robust high powerdensity machines capable of operating at high motor and inverter efficiencies over wide speed ranges, including considerable ranges of constant-power operation. The magnet cost is minimized by the low magnet weight requirements of the IPM design. The impact of the buried-magnet configuration on the motor's electromagnetic characteristics is discussed. The rotor magnetic circuit saliency preferentially increases the quadrature-axis inductance and introduces a reluctance torque term into the IPM motor's torque equation. The electrical excitation requirements for the IPM synchronous motor are also discussed. The control of the sinusoidal phase currents in magnitude and phase angle with respect to the rotor orientation provides a means for achieving smooth responsive torque control. A basic feedforward algorithm for executing this type of current vector torque control is discussed, including the implications of current regulator saturation at high speeds. The key results are illustrated using a combination of simulation and prototype IPM drive measurements.
Permanent-magnet machines using concentrated windings are gaining popularity at the expense of distributed windings in various applications, mainly due to cost savings. The result is often an increased amount of parasitic effects like ripple torque, alternating magnetic fields in the rotor, unbalanced radial forces, and magnetic noise. This paper describes the reasons for the parasitic effects, in which machine topologies are particularly sensitive, and suggests measures in order to reduce their importance. Both traditional and modular concentrated windings are analyzed, as well as double-layer and single-layer windings. Measurements on a prototype motor and three commercial servomotors have demonstrated that modular motors are favorable regarding ripple torque minimization.
The usual uncoupled d - q model of salient pole synchronous machines (Park's model) may be insufficient for accurate modeling of buried magnet permanent magnet machines. The addition of a nonbilateral coupling between the direct and quadrature axis equivalent circuits is shown to improve the steady-state model greatly. The cross coupling reactance has important implications in improving operation in the constant horsepower mode. In particular, it is demonstrated that the cross coupling term acts to reduce the effective internal voltage so that some field weakening can be achieved. The results should be useful in permanent magnet machine design for variable speed drive applications.
Permanent-magnet-assisted synchronous reluctance motors are well suited to zero-speed sensorless control because of their inherently salient behavior. However, the cross-saturation effect can lead to large errors on the position estimate, which is based on the differential anisotropy. These errors are quantified in this paper as a function of the working point. The errors that are calculated are then found to be in good accordance with the purposely obtained experimental measurements
A design approach oriented to the minimization of torque ripple is
presented for synchronous reluctance motors of the transverse-laminated
type. First, the possible types of rotors are classified and the more
suited rotor structure is evidenced, to be matched to a given stator.
Then, the inner rotor design is described, pointing out the low-ripple
measures. Lastly, experimental results are given from three different
rotors; they confirm the validity of the proposed approach
Permanent magnet synchronous (PM) motors can be applied to applications requiring constant power operation, such as traction and spindle drives by means of flux-weakening control. In a PM motor drive system with flux-weakening control, the motor parameters are used to produce the current vector command. The motor parameters vary because of magnetic saturation and as a result, the control performances are affected by the magnetic saturation. In this paper, the effects of magnetic saturation are examined and the control system considering the magnetic saturation is proposed. The performances of the proposed control system are examined by simulations and the experimental results with respect to the prototype interior permanent magnet synchronous motor.
A constant-parameter equivalent circuit model that neglects motor
losses is used to determine the effects of direct and quadrature
reactances and open-circuit voltage on the power capability of
salient-pole permanent-magnet motors in variable-speed drive
applications. It is shown that peak power capability over a range of
speeds can be obtained by proper control of the magnitude and phase of
the armature current. Due to the voltage constraint imposed at the motor
terminals, the power capability will fall to zero for most motor designs
at a given high speed. A simple relationship between the motor
open-circuit voltage and the direct axis reactance is derived to obtain
motor designs that, even with this voltage constraint in place, extend
their theoretical power capability, neglecting losses, to infinite
speed. All results are presented in normalized curves using a per-unit
system
Design criteria of an IPM machine suitable for field-weakened operation
- A Fratta
- A Vagati
- F Villata
A. Fratta, A. Vagati, and F. Villata, "Design criteria of an IPM machine suitable for field-weakened operation," in Proc. ICEM, Sep. 1990,
pp. 1059-1064.
Permanent magnet assisted synchronous reluctance drive for constant-power application: Drive power limit
- A Fratta
- A Vagati
- F Villata
A. Fratta, A. Vagati, and F. Villata, "Permanent magnet assisted synchronous reluctance drive for constant-power application: Drive power limit,"
in Proc. Intell. Motion Eur. Conf., PCIM, Nurnberg, Germany, Apr. 1992,
pp. 196-203.