A novel consequent pole hybrid magnet vernier memory machine for automotive applications

Low-speed direct-drive gearless machines are highly desirable for electric vehicle/hybrid electric vehicle (EV/HEV) propulsion due to the elimination of the associated gear wear, oil maintenance and acoustic problems. Conventional gearless direct-drive permanent magnet (PM) machines generally suffer from heavy weight, structural bulkiness, and lubrication problems. Due to the “magnetic-gearing” effect, magnetically geared machines (MGMs) were widely researched and recognized as a promising solution for traction applications. Since abundant asynchronous field harmonics are excited by modulating iron poles, which are directly involved in torque transmission. MGMs have the distinct synergies of magnetic gears and PM machines, i.e. high torque density, high efficiency and mechanical compactness [1]. Amongst MGM topologies, Vernier machines (VMs) with simpler mechanical assembly are more favorable for safety-critical applications compared to MGMs with multiple air-gaps. Meanwhile, owing to the uncontrollable PM flux in conventional VMs, hybrid excitation was introduced to VMs so as to extend constant-power operating range and alleviate inverter requirement [3], but continuous excitation copper loss is inevitably incurred, which will reduce the operating efficiency. On the other hand, memory machines [4] equipped with either single low-coercive force (LCF) or hybrid magnets were extensively investigated due to the elimination of the associated excitation loss during the flux adjustment, thus they enable high efficiency operation within a wide range of speeds and loads.