Toshiro Higaki

Motor design considerations and test results of an interior permanent magnet synchronous motor for electric vehicles

This paper describes the high performance motor design of an interior permanent magnet synchronous motor (IPM motor) for electric vehicles. The authors examined the differences in motor characteristics based on how the magnets were embedded. For this comparison, they set conditions so that the volume of magnets remained constant, and they used both computer simulation and experiments with a prototype motor. As a result, they were able to develop a double layer IPM synchronous motor, which has two layers of magnets embedded lengthwise in the radial direction in the rotor. The q-axis flux path can be expanded by using an IPM rotor with magnets divided into two layers with the separation lengthwise at the rotor radius. An evaluation of prototype motors confirmed that a double-layer IPM motor produces a 10 percent or more increase in the torque generated compared to a single-layer IPM motor using the same current. Also, the high efficiency operating region (min. 90%) was a minimum of 10% wider than the single layer IPM motor. However, reluctance torque of a double layer IPM motor with concentrated winding cannot be designed as high as that of a similar motor with distributed winding. This is because the inductance difference between the d and q-axes cannot be sufficiently increased in this former. Here, it was learned that a concentrated winding is inferior to a distributed winding both in terms of generated torque and the constant power region size.

High performance synchronous reluctance motor with multi-flux barrier for the appliance industry

Advances in power electronics and machining mean that reluctance motors have now become the focus of new studies. Research and development is pursuing two different tracks. One targets what is referred to as a switched reductance motor which uses a pulse signal to drive a salient-pole rotor. The other targets a synchronous reluctance motor (SynRM) which uses a sinusoidal wave to drive a rotor which is constructed with several flux barriers. The stator winding of the latter is of the same specifications as that used in an induction motor or a brushless motor which utilizes permanent magnets. It also carries the merit of effectively utilizing a conventional inverter due to the sinusoidal wave drive. For what regards rotor construction of this type of motor, Lipo, Miller, Boldea, Yagati and others have enthusiastically researched an axially laminated construction which features layers of electromagnetic iron plate in the rotors axial direction for the purpose of improving saliency ratio. However, many of these have not clarified the relationship between flux barrier construction and motor efficiency. This paper reports on simulations and experiments using a prototype, in which flux barrier construction and design optimization were investigated in consideration of machining distortion and other factors, as part of studies into making a highly efficient multi-flux barrier SynRM. It is also reported that the prototype model proved to be 6% more efficient than an induction motor with the same inverter drive.

Rotor design and control method of synchronous reluctance motor with multiflux barrier

To design the rotor of a synchronous reluctance motor with multiple flux barriers, the studies of the number of barriers, bridge width and other elements are important. It is found that a 6-layer configuration is best in terms of efficiency. In performance tests, a prototype efficiency is 6[%] higher than a conventional inverter-driven induction motor. The rotor also rotate at speeds in excess of 10,000 [r/min] because magnetic and nonmagnetic parts were built into a single body made of alloy.

High performance design of an interior permanent magnet synchronous reluctance motor for electric vehicles

We have examined the optimum rotor design of an interior permanent magnet motor (IPM motor) for electric vehicles. By using double-layer magnets embedded into the rotor with the layers separated in the direction of the rotor radius, we have been able to construct a rotor that takes greatest advantage of reluctance torque, resulting in a 10 percent torque increase over the conventional IPM motor, which uses only a single-layer of magnets in the rotor.

Magnet design and motor performances of a double‐layer interior permanent magnet synchronous motor

In this paper we discuss the results of our investigation of the interior permanent magnet synchronous motor (IPM), with permanent magnets embedded in the rotor, and particularly the double-layer IPM synchronous motor, which has two layers of magnets embedded in the rotor, layered in the radial direction. For this investigation, we studied the arrangement of permanent magnets both through simulation and by experiments with a prototype. The results concerning the form of the magnets clearly show the advantages of the reverse arc configuration, which makes it possible to increase the surface area creating magnetic flux. We further determined that to maximize both the q-axis flux and the flux of the permanent magnets, the optimum width of the q-axis flux path between the magnets for the motor investigated here is 2 mm. The results also clearly show that chamfering the ends of magnets is effective in achieving better utilization of the q-axis flux.© 1999 Scripta Technica, Electr Eng Jpn, 128(1): 62–69, 1999