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Proposed arrangement of a micro-horizontal-axis wind turbine (HAWT) system using an outer-rotor AFPMSG.
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This paper presents a unique axial-flux permanent-magnet synchronous generator (AFPMSG), which is suitable for both vertical-axis and horizontal-axis wind turbine generation systems. An outer-rotor design facilitates direct coupling of the generator to the wind turbine, while a coreless armature eliminates the magnetic pull between the stationary a...
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... small-scale wind-turbine generator systems are proposed in this paper. Fig. 1 shows a horizontal-axis wind turbine sys- tem (HAWT) that employs the proposed direct-coupled AF- PMSG. To facilitate direct coupling of the generator to the tur- bine blades, an outer-rotor machine configuration is used. The rotor rotates about a stationary shaft, which is supported on a tower by means of a yaw mechanism. The turbine ...
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... of the generator involved sandwiching the stator disk winding between the two rotor frames (one with surface- mounted magnets and one without). Jacking bolts were used to control the separation between the rotor frames by using the screwed holes provided on each motor frame (which are visible in Fig. 12). This prevented the two rotor frames from acciden- tally snapping into each other during the assembly process due to the strong magnetic ...
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... the surface-mounted NdFeB magnets have a recoil per- meability close to that of air, the AFPMSG may be regarded as a cylindrical-rotor synchronous machine with a constant field excitation. Fig. 11 shows the per-phase equivalent circuit of the generator when supplying an isolated resistive load, where E F is the no-load terminal voltage, R is the armature resistance, X s is the synchronous reactance, R L is the load resistance, and V is the terminal voltage; all being per-phase quantities. From the circuit, the current, terminal ...
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... EXPERIMENTAL RESULTS AND DISCUSSION Fig. 12 shows the setup for experimental investigations on the AFPMSG. The shaft of the machine was mounted on a special test rig so that the rotor frame can turn freely. Provisions were made on the motor frame for coupling the generator rotor to a dynamometer motor drive by means of a belt transmission. The turbine is therefore emulated by ...
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... current. When the speed is reduced to 300 r/min, the voltage drop between no load and full load increases to 50%, and at rated current the output power is only 110 W. Due to the relatively large armature resistance, maximum efficiency of the machine occurs at low values of load current. A maximum efficiency of 79.0% can be achieved at 600 r/min. Fig. 14(a)-(c) shows the variations of terminal voltage, output power, and efficiency of the experimental AFPMSG with speed when the load resistance is constant. The output voltage varies almost linearly with the rotor speed, while the output power varies approximately with the square of the rotor speed. The efficiency, however, is only slightly ...
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... from 350 to 700 r/min. The close agreement between the voltage-current and power-current characteristics confirms the theory developed in Section V of the paper. Experimental values of efficiency, how- ever, correlate less well with the computed values due to the difficulty in accurately determining the losses in the belt trans- mission. Fig. 15(a) and (b) shows, respectively, the line voltage wave- forms of the AFPMSG at no load and when delivering a current of 6.1 A to a resistive load. The waveforms are practically sinu- soidal. From a measurement using a harmonic analyzer, it was found that in each case there was mainly a 1.4% 5th harmonic and a 0.2% 7th harmonic, with a ...
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Citations
... As the fixed speed generators are running at the same speed for different wind speeds, the fixed speed systems are less efficient than variable speed systems. Mostly, the generators used in variable speed systems are doubly fed induction generators (DFIGs) and synchronous generators (SGs) (Chan and Lai, 2007). At present, due to the development of permanent magnet characteristics and price reduction, the direct-drive permanent magnet generator (PMG) becomes more attractive. ...
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... The Axial Flux Permanent Generators (AFPMG) have started to be commonly used in private, domestic wind turbines [1][2][3][4] but also in traction and low-speed drives [5,6], which is presented in other publications [7,8]. The operation of AFPMG depends on many aspects. ...
In this article, the field (FEM) and analytical analyses were used for the optimal selection of magnets material for the Axial Flux Permanent Magnet Generator (AFPMG), without building the prototype before. The tested generator is an axial flux machine which consists of a single stator and two rotor discs with Permanent Magnets (PM). Three-dimensional (3D) ANSYS Maxwell package was used for magnetostatic and transient field (FEM) simulations. Two types of PM were selected for the analysis: Ceramic (also known as “Ferrite”) magnets made from Strontium Ferrite powder and Neodymium Iron Boron magnets (NdFeB). The authors compared obtained electromotive forces (EMF) and generator powers for selected magnets materials, performed FFT analyses of voltages and currents and indicated the optimal solutions. In addition to the operational properties of the AFPMG, the magnet and manufacturing costs were compared.
... In pico hydropower plants AFPMGS are commonly used, which can be realized with one or several rotors and stators, depending on the power output required for the application [39]. Moreover, for high turbine rotation speeds, it is also possible to realize AFPMGS with a high number of polar pairs. ...
A pico hydropower plant is an energy harvesting system that allows energy production using the power of the water flowing in small watercourses, and in water distribution network. Axial Flow Flux Permanent Magnet Synchronous Generator (AFPMSG) are particularly suitable for this application, being efficient machines that achieve high power with small dimensions. This paper presents a parametrical study of several configurations and topologies of three-phase and single-phase AFPMSG, for pico hydropower application, to assess the most suitable dimensional characteristics for the most energy production using a safe voltage of 25 V. The AFPMSGs here considered has a simple single stator and rotor configuration, commercial-type permanent magnets, and concentric windings, to facilitate their cost-effective construction and the spread of their use also in developing countries. For each AFPMSG considered, the power output was calculated using 3-D modelling and Finite Element Analysis; besides, the different parameters and features that affect the power output were evaluated at different rotational speeds. The results achieving a power density up to 100 W/cm3, at 1000 rpm with energy produced to 1.7 kWh/day.
... For VAWT generators, special characteristics are desired, such as wide wind speed range capture capability, low torque ripple, high efficiency, and high power density. Permanent magnet axial-flux generators have advantages of short axial length, high power density, and easy module combination of multiple generators according to various power requirements and are suitable for direct driving VAWTs [5,6]. However, for direct coupling of the high-power axial-flux permanent magnet synchronous generators and wind turbines, a more difficult starting of the wind turbine is inevitable, especially at a lower wind speed section. ...
Axial‐flux wind generators have advantages of high ratio of generator diameter to generator length and high possibility of modular construction, which make them suitable for use in vertical‐axis wind turbines. The design optimisation and analysis of an asymmetric‐primary axial‐flux hybrid‐excitation generator that can provide a controllable suspension magnetic levitation force to compensate for the ripple of axial force fluctuation are described. First, the mechanical topological operation principle of the proposed generator is introduced, and four generators with different magnetic field modulation ratios and winding distributions are investigated. Second, the levitation force and the torque model are based on the d/q axes dynamic mathematical model. Four generators are compared based on no‐load performance. Considering the polar arc coefficient, this study analyzes the no‐load performance. In addition, comprehensive analyses of the on‐load performance under two typical load conditions are conducted. Based on simulation results and by integrating the magnetic field modulation ratio, tooth width, and permanent magnet thickness, the optimal design of a 12s22p generator is obtained. Finally, a prototype of the 12s22p generator is manufactured and tested in a laboratory situation under on‐load and no‐load conditions. All of the findings are consistent with the simulation results.
... In this equation, B u is the average of the surface flux density of a permanent magnet, which is 1.25 Tesla for the NdFeB magnet [8]. Moreover, P is the number of poles, λ is the AFPM diameter ratio (D i /D o ), and B cr is the maximum permissible flux density for the rotor core, which is determined for soft steel alloys at frequencies above 40 Hz by the following Equation [27]: The core of rotor disc in the proposed design is made from M19-29G steel, which is a ferromagnetic material with nonlinear behavior. ...
... L pm is the axial thickness of the permanent magnet, which is a highly effective quantity in the design of permanent magnet machines. This parameter depends on the air gap and thickness of the coil, as given in Equation (16) [8,10]: ...
... For instance, the arc-to-pole ratio (α p ) is considered to be in the range of 0.57-0.75 to have the minimum leakage flux and to create a sinusoidal flux density. Values above 0.75 for α p can lead to a magnetic short-circuit in the rotor [8]. ...
This paper addresses an integrated and developed approach to the design of an Axial Flux Permanent Magnet Wind Generator (AFPMWG). The proposed analytical method of design employs the size equations and precise inductance calculations simultaneously, as well as considering the mechanical constraints of the back-iron disc of the rotor. An Elitist Genetic Algorithm (EGA), such as a high capability optimization method, has been used to solve the equations and design of a wind generator with predefined rating power. The objectives of the coreless AFPMWG design process are minimizing the magnet consumption, maximizing machine efficiency, and achieving maximum sinusoidal induction voltage, considering the wind properties of the geographical area of utilization. The optimal calculation of the permanent magnet thickness is also taken into consideration in this work. The flux density distribution in all parts of the machine has been investigated for the magnetic saturation phenomenon. In this regard, special attention is paid to rotor back discs, which are made from nonlinear material with an optimum thickness. The inductance of the leakage flux of the coreless machine has been considered by parallel computation via the Finite Element Method (FEM) and analytical equations. Finally, three-dimensional and two-dimensional finite element analyses are used to validate the performance of the machine design according to the characteristics of Iran wind resources. The results show the high ability of the proposed approach in AFPMWG design and in considering the objectives and constraints carefully.
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... One may observe an increasing interest in the application of electric machines of the axial flow of magnetic field in many industrial applications as an alternative to machines of conventional construction. The reason for this situation is that the geometric features of these devices (very big ratio of machine diameter to its axial length) predisposes this type of constructions for such applications as integrated alternators with a combustion engine [1], drive systems of electric vehicles [2][3][4][5], or generators functioning in systems with wind turbines [6][7][8] in particular with the vertical axis of rotation [9,10]. With regard to such a wide range of various applications, there have been many variants of machine constructions with axial flow permanent magnets (AFPM) [11][12][13][14][15][16]. ...
... The i d g = 0 reflects a lack of current excitation. The q component of the stator current is determined by the PI regulators in accordance with (6) ...
The article presents an innovative construction of the Axial Flux Permanent Magnet (AFPM) machine designed for generator performance, which provides the shape of induced voltage that enables estimation of the speed and rotational angle of the machine rotor. Design solutions were proposed, the aim of which is to limit energy losses as a result of the occurrence of eddy currents. The method of direct estimation of the value of the rotational speed and rotational angle of the machine rotor was proposed and investigated on the basis of the measurements of induced voltages and machine phase currents. The advantage of the machine is the utilization of simple and easy-to-use computational procedures. The acquired results were compared with the results obtained for estimation performed by using the Unscented Kalman Filter (UKF)
... On the other hand, axial-flux permanent magnet (AFPM) machines have been employed in a large variety of applications such as hybrid electric vehicles, washing machines, aircraft propulsion, combined heat and power, wind energy generation, portable gensets, starter/alternators, hard disk drive, flywheel energy storage, and wind and pico-hydro turbines (Capponi et al., 2012). In case of pico-hydropower, AFPM offers the benefit of high number of the poles that is befitting for low-speed applications (Chan & Lai, 2007). AFPM machines with high power density can be obtained with the use of rare earth permanent magnets (PM) (Javadi & Mirsalim, 2008). ...
... The ratio of inner and outer diameter (λ) is considered as another important parameter for AFPM machine design in maximizing the output power. From previous research, optimized values of λ were chosen for different AFPM design, out of which, 1/√3 and 1/√2.5 are common for the most of the configurations (Chan & Lai, 2007;Daghigh et al., 2017;Upadhyay & Rajagopal, 2006). In the present study, the value of λ is chosen 1/√3, for getting maximum power. ...
An axial flux permanent magnet (AFPM) generator is known to be a good candidate for both low- and high-speed applications. In this paper, a comprehensive comparison of four coreless AFPM generators is presented with conventional and Halbach magnet arrangement combined with iron and ironless rotor (epoxy). With the same coreless stator structure, four different AFPM generators with different rotor magnet arrangement and materials are compared in terms of voltage, current, power, machine weight, and power density. The analytical design approach is first presented and is subsequently validated using ANSYS Maxwell electromagnetic finite element analysis (FEA) software. Results show that AFPM machine with fully coreless topology using Halbach array with epoxy rotor can deliver similar power density but has a lower cost compared to conventional magnet array with iron rotor. Hence, this topology is favorable for low power low cost applications.
... Interest in Permanent Magnet (PM) synchronous generators is associated with a global trend to support local energy supplied with renewable energy sources such as wind or water power, in which synchronous generators excited by permanent magnets are being increasingly applied [1][2][3][4][5][6]. Generators in this class of applications typically have a cylindrical rotor with surface-mounted magnets, but axial magnetic flux disc generator solutions are also very popular [7,8]. ...
In this paper, an application of the Harmonic Balance Method (HBM) for analysis of Axial Flux Permanent Magnet Generator (AFPMG) is carried out. Particular attention was paid to development of mathematical model equations allowing to estimate the machine properties, without having to use quantitative solutions. The methodology used here allowed for precise determination of Fourier spectra with respect to winding currents and electromagnetic torque (both quantitatively and qualitatively) in steady state operation. Analyses of space harmonic interaction in steady states were presented for the three-phase AFPMG. Satisfactory convergence was between the results of calculations and measurements which confirmed the initial assumption that the developed circuit models of AFPMG are sufficiently accurate and can be useful in the diagnostic analyses, tests and the final stages of the design process.
... Direct-drive turbines without a gearbox have been extensively studied for their high reliability, low maintenance cost, and high efficiency [6]. Compared with traditional radial flux rotation generators, axial flux generators have a higher generator diameter-to-length ratio and are suitable for direct coupled wind turbine applications, such as vertical axis and directcoupled wind turbines [7][8][9]. These generators also have a large power-to-weight ratio, highly flexible field and winding design, improved cooling, and potential application in modular construction. ...
Axis-flux wind generators are widely used in vertical axis wind turbines given their high generator diameter-to-length and power-to-weight ratios, flexible field and winding design, improved cooling, and possibility of modular construction. In this paper, an asymmetric-primary axis-flux hybrid-excitation generator (APAFHG) is proposed to provide a controllable suspension maglev force that compensates for the ripple of axial force fluctuation. First, the operation principle of the proposed generator is introduced. No-load performance influenced by direct current (DC) excitation is obtained by using the 3D finite element method (3D-FEM). Second, the load performances are analyzed under two typical operation statuses, namely, symmetrical pure resistance load and id=0 control strategy load. An alternating current (AC) excitation method is then comparatively analyzed to increase the output power under the maximum armature current. Third, based on the dq axes dynamic mathematical model, the quantitative calculations of levitation force and torque characteristics are deprived and then tested and verified by using the finite element analysis results. These results show that the proposed generator can be implemented for the decoupling control operation of power and levitation forces and is suitable for vertical axis wind turbines.
