With the increasing power and speed of 24v brushless DC motor, the rotor eddy current loss leads to the superheat demagnetization of permanent magnets, which becomes the key factor restricting the high power density of brushless DC motor. This is due to the heat conduction between the rotor and the stator through the air gap, and the heat dissipation condition is poor, resulting in the rotor temperature higher than that of the stator. High rotor eddy current loss is easy to cause high temperature of the rotor, which increases the risk of overheating and magnetic loss of permanent magnets on the rotor.
Therefore, reducing the rotor eddy current loss to reduce the rotor heating, and reducing the copper consumption to reduce the stator temperature to facilitate the heat dissipation of the rotor, is conducive to the increase of power density of 24v brushless DC motor.
The time harmonics of armature current are the main factors that cause eddy current loss and increase effective current. Compared with the sine wave driving mode, the square wave driving mode will bring larger current time harmonics. The discontinuous commutation of stator current is an important cause of current time harmonics and rotor heating. At present, the research methods of 24v brushless DC motor rotor eddy current loss and copper loss mainly include rotor structure research to change eddy current induction path, and driving mode research to reduce the time harmonic of armature current.