Flux Squeeze Reluctance Motor Improves Partial Load Efficiency in Vehicle Traction Applications

Permanent magnet excited (PMSM), externally excited synchronous machines and asynchronous machines (ASM) are state of the art in vehicle traction applications. Currently, the externally excited synchronous machine (EESM) has a high market share in Europe and also asynchronous motors are encountered in many battery electric (BEV) vehicle models still. However, the PMSM becomes the dominant type of vehicle traction drive in the product portfolios of the leading car manufacturers. The reason for this trend is that PMSM machines deliver torque at high efficiency over a wide range of load situations with no need for expensive rotor cooling in the typical load profile of a road vehicle. The main drawback of PMSMs: the mining of rare earth materials produces very harmful greenhouse gases. In the recent years, attempts were made to advance the switched reluctance motor (SRM) in order to make it suitable for traction applications. The advantage of SRM is that no permanent magnets are needed and its production cost is low. The most significant disadvantages are high torque ripple, noise, low efficiency in partial load situations and necessity for expensive rotor cooling. In this paper, the approach of a novel motor concept is shown that relies on seven phases. It overcomes the common drawbacks of SRM is a very promising concept for the next generation of electric vehicles.