[Show abstract][Hide abstract] ABSTRACT: The authors have devised a new method to decrease high-frequency harmonics in a specific frequency band by modifying the switching transient slope. In previous studies, there were several problems in applying modified transient pulse width modulation (MT-PWM) to actual converters. In this paper, three problems are solved using an improved MT-PWM method. First, the MT-PWM signal was obtained using a trial-and-error approach that involved complex computation procedures in the previous studies. In this paper, a new calculation procedure for obtaining the MT-PWM waveform using a simple calculation is proposed. Second, a new controller (drain-source voltage controller) based on voltage feedback is proposed in order to realize a modified switching transient to increase the stability of the switching operation. Third, the dependency of MT-PWM on source voltage variation is investigated in order to implement MT-PWM in an actual step-down converter. From this result, the concept of a new type of controller with the source voltage variation taken into consideration is proposed. Finally, the authors attempted to apply MT-PWM to an H-bridge converter to expand the application of MT-PWM. An H-bridge converter with MT-PWM for a dc motor drive is successfully operated in an experiment.
No preview · Article · Feb 2016 · Electrical Engineering in Japan
[Show abstract][Hide abstract] ABSTRACT: In recent years, increasing rotational speed is required for reducing size and cost of systems applying high-output motors. However, it is difficult for mechanical bearings to suspend a shaft of the high-output motor rotating at high speed due to friction and wear caused by mechanical contact. On the other hand, magnetic bearings (MBs) are useful for shaft suspension of the high-output motor rotating at high speed and developed actively, because the MBs can suspend the shaft without mechanical contact .
No preview · Article · Jul 2015 · IEEE Transactions on Magnetics
[Show abstract][Hide abstract] ABSTRACT: A new switched reluctance (SR) generator was designed for possible application in hybrid electric vehicles. The proposed generator was designed to be mostly competitive with the target interior permanent-magnet (IPM) generator currently used in mass-produced hybrid vehicles. The energy efficiencies of the SR and IPM generators were compared in typical driving cycles, such as US06, HWFET, and UDDS modes. We found that the energy efficiency of the SR generator was close to the IPM generator in high-speed driving cycles because the SR generator has no iron loss during the generator idling period due to the fact that it has no PM.
No preview · Article · Jul 2015 · IEEE Transactions on Industry Applications
[Show abstract][Hide abstract] ABSTRACT: This paper introduces a novel decoupling method for current regulation in high-speed bearingless motors using AC suspension current. The frequency of the suspension current increases in proportion to rotating speed in the bearingless motors using AC suspension current, and regulating the suspension current is difficult at high speeds rotation. In previous research, a current regulation method is used that convert AC to DC using a rotating coordinate system. However, that method has interference voltages which make the system unstable. In this paper, we propose a novel decoupling method for the suspension current regulation. In the experiment, stable levitation of the bearingless motor is achieved at 30000 min-1 by using the proposed decoupling controller.
[Show abstract][Hide abstract] ABSTRACT: A centrifugal pump that employs a bearingless motor with 5-axis active control has been developed. In this paper, a novel bearingless canned motor pump is proposed, and differences from the conventional structure are explained. A key difference between the proposed and conventional bearingless canned motor pumps is the use of passive magnetic bearings; in the proposed pump, the amount of permanent magnets (PMs) is reduced by 30% and the length of the rotor is shortened. Despite the decrease in the total volume of PMs, the proposed structure can generate large suspension forces and high torque compared with the conventional design by the use of the passive magnetic bearings. In addition, levitation and rotation experiments demonstrated that the proposed motor is suitable for use as a bearingless canned motor pump.
[Show abstract][Hide abstract] ABSTRACT: Powerful rare earth permanent magnets (PMs) are generally utilized in in-wheel PM synchronous motors for electric city commuters. However, the use of rare earth PMs has become undesirable due to high prices. An in-wheel PM synchronous motor that does not employ rare earth PMs therefore needs to be developed. We have previously proposed an in-wheel axial-gap motor that can generate high torque density and has features such as a coreless rotor structure with ferrite PMs and a reduction gearbox inside the stator. Through further research, we confirmed that suppression of eddy current loss arising in the rotor is important for attaining higher efficiency in high output motors. Accordingly, here we introduce an improved rotor with slits which can suppress eddy current loss. The results of experiments on a new prototype show that the improved rotor is effective in producing high efficiency and can satisfy the properties demanded of the in-wheel motors for electric city commuters.
[Show abstract][Hide abstract] ABSTRACT: The increased price and the limited supply of rare-earth materials have been recognized as a problem by the international clean energy community. Rare-earth permanent magnets are widely used in electrical motors in hybrid and pure electrical vehicles, which are prized for improving fuel efficiency and reducing carbon dioxide (CO2) emissions. Such motors must have characteristics of high efficiency, compactness, and high torque density, as well as a wide range of operating speeds. So far, these demands have not been achieved without the use of rare-earth permanent magnets. Here, we show that a switched reluctance motor that is competitive with rare-earth permanent-magnet motors can be designed. The developed motor contains no rare-earth permanent magnets, but rather, employs high-silicon steel with low iron loss to improve efficiency. Experiments showed that the developed motor has competitive or better efficiency, torque density, compactness, and range of operating speeds compared with a standard rare-earth permanent-magnet motor. Our results demonstrate how a rare-earth-free motor could be developed to be competitive with rare-earth permanent-magnet motors, for use as a more affordable and sustainable alternative, not only in electric and hybrid vehicles, but also in the wide variety of industrial applications.
No preview · Article · Aug 2014 · IEEE Transactions on Energy Conversion
[Show abstract][Hide abstract] ABSTRACT: The disturbance voltage of air conditioners may be degraded, depending on the combination of the outdoor and indoor units. This paper describes a technique to simulate the disturbance voltage of an air conditioner and examines the propagation path of conductive noise when two or more indoor units are connected to the outdoor unit.
[Show abstract][Hide abstract] ABSTRACT: DC-DC converters of hybrid vehicles and electric vehicles are required to become smaller and lighter for building roomy and light weight EV. High-frequency switching can be used to miniaturize DC-DC converter. However, the influence of the skin effect and the eddy current become large. Parallel operation of converter is often for current applications using multiple winding transformers in order to reduce of skin effect. However, it is difficult to equalize the each current of converter due to unbalance of winding resistance, drop voltage of diodes and so on. In this paper, the parallel LLC converter applied a current-balancing high-frequency transformer is proposed. The proposed converter can realize nearly equal current even if the stray impedance of secondary circuit of LLC are unbalanced.
[Show abstract][Hide abstract] ABSTRACT: In general, the in-wheel type permanent magnet synchronous motor (PMSM) for electric city commuters uses powerful rare earth permanent magnets (PMs). However, the employment of the rare earth PMs should be reduced due to high prices. Therefore, it is important to develop an in-wheel PMSM that does not use the rare earth PMs. We proposed 5kW in-wheel type axial gap motor that can generate high torque density and has features such as a coreless rotor structure with ferrite PMs and a reduction gearbox in the inner side of the stator. And we have presented details of experimental results on a prototype. So, in this paper, in order to achieve further higher power output, we considered a 10 kW in-wheel motor with the proposed structure. The motor with 10-kW output was examined by means of using 3D-FEM and experimental results in order to attain the further higher power as a rare earth free motor.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a new circuit configuration of the active common-noise canceler (ACC), which is used to reduce electromagnetic interference of a space vector modulation (SVPWM) inverter. The original ACC, which was proposed by the authors, cancels all components of the common-mode voltage and, therefore, cannot be used in an SVPWM inverter owing to the low-frequency component of the common-mode (zero-sequence) voltage. The proposed ACC cancels only the high-frequency component of the common-mode voltage so it can be used in SVPWM inverters. Furthermore, the high-frequency carrier makes a large contribution to downsizing the common-mode transformer. To confirm the suitability and usefulness of the proposed ACC, an experimental system including a 100-kHz SVPWM inverter was constructed and tested. The experimental results show that the proposed ACC can reduce the high-frequency component of the common-mode voltage.
[Show abstract][Hide abstract] ABSTRACT: In light of global warming and the rapidly increasing prices of rare earths, electric vehicles with motors free of rare earths are needed. We are therefore developing an interior permanent magnet synchronous motor (IPMSM) that utilizes ferrite permanent magnets. Because the residual flux density of a ferrite magnet is lower than that of a rare earth magnet, we have adopted a spoke-type IPMSM with radially arranged ferrite magnets. This paper proposes two rotor structure designs for spoke-type IPMSMs with ferrite magnets, and presents the results of two-dimensional finite element analysis (FEA) for the two designs. The results indicate that the performance loss from using ferrite magnets can be moderated by effectively utilizing reluctance torque in a spoke-type IPMSM. Finally, a rotor structure that has sufficient performance to be usable in a traction motor free of rare earths is examined through experiments on a prototype and three-dimensional FEA.
[Show abstract][Hide abstract] ABSTRACT: Rare earth magnets that have a large energy product are generally used in high-efficiency interior permanent-magnet synchronous motors (IPMSMs). However, efficient rare-earth-free motors are needed because of problems such as the high prices of and export restrictions on rare earth materials. This paper introduces a ferrite-magnet spoke-type IPMSM that employs a W-shaped magnet placement in order to achieve high efficiency. The effectiveness of the W-shaped magnet placement is verified from the results of two-dimensional finite element analysis and experiments on a prototype.