Dynamic demagnetisation investigation for less-rare-earth flux switching permanent magnet motors considering three-phase short-circuit fault

This study presents dynamic demagnetisation investigations of less-rare-earth (LRE) flux switching permanent magnet (LRE-FSPM) motor under three-phase short-circuit (SC) fault. Owing to relatively low coercivity of ferrite PMs, it is necessary to investigate demagnetised risk of LRE PM motors. Actually, motors suffer from larger demagnetising risk under SC faults than normal conditions. Hence, it is essential for LRE PM motors to comprehensively investigate and enhance anti-demagnetisation capability during design stage. Here, by integrating electrical-magnetic field calculation and driving control circuit, dynamic demagnetisation characteristics of the LRE-FSPM motor under SC faults are calculated as an example. To fairly evaluate demagnetisation withstand capability of LRE-FSPM motor, the non-rare-earth (NRE)-FSPM motor is also presented and compared as a referenced motor. Then, the dynamic demagnetisation characteristics of two motors are analysed and compared, including demagnetising d-axis current, operating points, and demagnetised area. It is found that, the proposed LRE-FSPM motor exhibits improved operating points and less demagnetised area, which is only about one-third of that of NRE-FSPM motor. Finally, the demagnetisation calculation results not only verify the validity of dynamic demagnetisation investigation approach, but also prove the reasonability of LRE-FSPM motor, which provide a promising research path for the design of LRE PM motors.