A Drive Method of Brushless DC Motor to Decrease Rotor Eddy Current Loss and Copper Loss

The stator currant harmonics of brushless DC motor (BLDCM) are high in the square-wave drive method, which will increase rotor eddy-current loss and further raise the risk of rotor permanent magnet overheated demagnetization. The reliability of motor is also reduced. A novel method based on current planning for the BLDCM is proposed. In the method, the back-electromotive force (EMF) is considered as the state variable, the reference torque as a constraint condition, and the minimum phase currents as the optimization objectives. Then, the reference currents can be calculated. The current loop consists of the reference currents and two phase feedback currents. Analysis and simulations show that the rotor eddy-current loss and copper loss are lower than those of the square-wave drive method. Finally, taking an 82W BLDCM as the object, the model of rotor eddy-current loss and the test circuit are built to verify the proposed method.