A very high efficiency controller for an axial flux permanent magnet wheel drive in a solar powered vehicle

This paper describes the design, construction and testing of a very high efficiency controller for a vehicle traction system using an in-wheel axial flux permanent magnet machine. The testing and measurement of the controller is carried out using a simple, indirect calorimetric technique. This technique is very inexpensive, and is capable of very high accuracy. Specific issues addressed are the careful management of switching losses by choice of switching patterns, tradeoffs between current ramp amplitudes and switching rates, and management of the reverse recovery of the body diodes in the FET main switches. The resulting controller under race conditions can process 1 kW of power with total losses generally close to 1%.