Airgap Length Analysis of a 350 kw PM-Assisted Syn-Rel Machine for Heavy Duty EV Traction

Abstract

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.

Design and Analysis of Hybrid-Excitation Variable Flux Memory Motor for Traction Applications: Improving Output Power in High-Speed Area During Six-Step Operation Mode

“…However, as shown in Fig. 1 typical traction motors are prone to have a lower output power in the high-speed area than its peak point around the base speed [2], [3]. Accordingly, to improve the acceleration performance in high-speed areas, it is essential to increase the motor size.…”