Direct electric losses measurement for PM brushless machines

A new procedure for direct electric measurement of total losses in permanent magnet brushless AC machines is presented in this paper. The procedure is based on a back-to-back mechanical and electrical connection to allow for a single three-phase converter supply. The motors can be driven in speed as an equivalent machine, the current in the motors depends on the physical angular displacement between the two rotors. The power supplied by the converter in steady-state is the total power dissipated by the two motors. A simple algorithm to identify the current to mechanical angle relationship at a given speed is proposed. The proposed procedure is validated by an experimental setup adopting two low power torque motors.