Kyohei Kiyota

Design of Switched Reluctance Motor Competitive to 60-kW IPMSM in Third-Generation Hybrid Electric Vehicle

In this paper, a design of a switched reluctance motor (SRM) having competitive torque, power, speed range and efficiency of the interior permanent magnet synchronous motor (IPMSM) employed in the 2009 Toyota Prius has been investigated. The maximum torque of 207 Nm is needed up to the knee speed of 2768 r/min. The output power of 60 kW is required in the speed range from 2768 r/min to 13900 r/min. It is shown that the above requirements can be satisfied with a designed SRM, although, the current density and the weight are slightly increased. At the high speed, simulation results show that the output of the designed SRM is found to be greatly enhanced with respect to that in the IPMSM.

Development of a Rare-Earth-Free SR Motor With High Torque Density for Hybrid Vehicles

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.

Comparison of Test Result and Design Stage Prediction of Switched Reluctance Motor Competitive With 60-kW Rare-Earth PM Motor

A switched reluctance motor has been designed with identical outer dimensions, maximum torque, operating area, and maximum efficiency as rare-earth permanent-magnet motors used in the Toyota Prius. In this paper, a test machine has been constructed, and test results are presented over the entire speed range. The targets are torque of 207 N·m, a shaft output of 60 kW, and the maximum efficiency of 96%, as well as a speed range of 2768-13 900 r/min with an output of 60 kW and an outer diameter and an axial length of 264 and 112 mm, respectively. It is found that a shaft output of 100 kW is possible at high rotational speed under the voltage and current ratings. The possible operation area in a torque-speed plane is found to be enhanced. It is also found that the design stage prediction is close to the test results, except in two operation regions.

Comparison of the Test Result and 3D-FEM Analysis at the Knee Point of a 60 kW SRM for a HEV

The maximum torque values in computer analysis and experiment in the switched reluctance motor (SRM), having competitive torque density and efficiency with respect to the rare-earth permanent magnet motor employed in the 2009 Toyota Prius, have been compared. The SRM is highly saturated to provide the maximum torque for a short time; thus, the torque value tends to have considerable error of 15% even in the 3D FEM analysis with respect to experimental result because of the incomplete material setting. A comparison of the flux-linkage and current is also provided for consideration. The results of the 2D-FEM and 3D-FEM analysis as well as a test machine are presented. The maximum torque in the 3D-FEM analysis is shown to be within errors of 5.0% with respect to that in the test machine.

Comparison of energy consumption of SRM and IPMSM in automotive driving schedules

Permanent magnets with rare earth materials are widely used in interior permanent magnet synchronous motors (IPMSMs) in Hybrid Electric Vehicles (HEVs). The recent price rise of rare earth materials has become a serious concern. A Switched Reluctance Motor (SRM) is one of the candidates for HEV rare-earth-free-motors. An SRM has been developed with dimensions, maximum torque, operating area, and maximum efficiency that all compete with the IPMSM. The efficiency map of the SRM is different from that of the IPMSM; thus, direct comparison has been rather difficult. In this paper, a comparison of energy consumption between the SRM and the IPMSM using four standard driving schedules is carried out. In HWFET and NEDC driving schedules, the SRM is found to have better efficiency because its efficiency is high at the high-rotational-speed region.

Design of switched reluctance motor competitive to 60 kW IPMSM in third generation hybrid electric vehicle

In this paper, a design of a switched reluctance motor (SRM) having competitive torque, power, speed range and efficiency of the interior permanent magnet synchronous motor (IPMSM) employed in the 2009 Toyota Prius has been investigated. The maximum torque of 207 Nm is needed up to the knee speed of 2768 r/min. The output power of 60 kW is required in the speed range from 2768 r/min to 13900 r/min. It is shown that the above requirements can be satisfied with a designed SRM, although, the current density and the weight are slightly increased. At the high speed, simulation results show that the output of the designed SRM is found to be greatly enhanced with respect to that in the IPMSM.

Comparing Electric Motors: An Analysis Using Four Standard Driving Schedules

Permanent magnets with rare-earth materials are widely used in interior permanent magnet synchronous motors (IPMSMs) in hybrid electric vehicles (HEVs). The recent price increase in rare-earth materials has become a serious concern. A switched reluctance motor (SRM) is one of the candidates for HE V rare-earth-free motors. An SRM has been developed with dimensions, maximum torque, operating area, and maximum efficiency that all compete with the IPMSM. The efficiency map of the designed SRM is different from that of the IPMSM; thus, direct comparisons have been rather difficult. In this article, a comparison of the energy consumption between the SRM and the IPMSM using four standard driving schedules is carried out. In the Highway Fuel Economy Driving Schedule (HWFET) and the New European Driving Cycle (NEDC), the SRM is found to have better efficiency because its efficiency is high at the high rotational speed region.

Energy Efficiency of SR and IPM Generators for Hybrid Electric Vehicle

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.

Cylindrical rotor design for acoustic noise and windage loss reduction in switched reluctance motor for HEV applications

A switched reluctance motor (SRM) is one of the candidates of rare-earth-free motors for hybrid electric vehicles (HEVs). An SRM has been developed with same interior permanent magnet synchronous motor (IPMSM) dimensions having competitive maximum torque, operating area, and maximum efficiency. However, this SRM has a windage loss of 1.3 kW due to the salient poles of the SRM driven at the maximum rotational speed. In addition, considerable acoustic noise is caused by the salient poles. In this paper, a simple design of a cylindrical outer shape rotor is proposed, and a comparison with the conventional SRM rotor is carried out. It is found that the efficiency is improved due to the windage loss reduction. It is also found that the acoustic noise is significantly reduced in the proposed rotor design.

Estimation and comparison of the windage loss of a 60 kW Switched Reluctance Motor for hybrid electric vehicles

A Switched Reluctance Motor (SRM) has been designed with outer dimensions, maximum torque, operating area, and maximum efficiency identical to the rare-earth PM motor used in the Toyota Prius. However, an SRM has salient poles in the rotor; thus, additional windage loss is generated. In this paper, estimation of the windage loss of the SRM is carried out. Then, a comparison to the machine test result is carried out. The influence of the windage loss is identified.