Investigation of Efficiency Enhancement of a Wound-Field Flux Switching Motor by the Synchronous Reluctance Motor Drive

Wound-Field Flux Switching Motors have high power density among rare-earth-free motors and are attracting attention as alternatives to Permanent Magnet Synchronous Motors for the traction applications of hybrid electric vehicles. However, their efficiency deteriorates in regions where iron loss is dominant. Synchronous Reluctance Motors, incidentally, have low iron loss, although, they are not suitable for high power output. This paper proposes driving a wound-field flux switching motor as a synchronous reluctance motor by changing the current control without changing the mechanical structure to enhance the efficiency all over the operating area. It is found that switching to synchronous reluctance motor operation improves efficiency in the high-speed low-torque region compared to the wound-field flux switching motor operation. The efficiency is improved in the wound-field flux switching motor operation in the low-speed medium-torque region compared to synchronous reluctance motor operation, indicating that switching can compensate for each weak point in the two operation modes.