Research on Energization Strategy to Reduce the Copper Loss of the Permanent-magnet Spherical Motor

In continuous operation mode, aiming at the problem that the harsh ventilation and cooling conditions of permanent-magnet spherical motor(PMSpM) affect the reliable operation and service life of the motor, several spin energization strategies that can output target torque exactly and avoid local overheating are proposed. A model of relationship between effective value of single coil current and steady-state temperature(I_RMS-T_steady) based on finite-element analysis(FEA) is established, and a method of indirectly measuring the coil temperature using a high-precision current sensor is proposed to verify the accuracy of the model. Based on this, three energization strategies of eccentric spin, minimum current sum and fixed excitation coils are analyzed. The latter two strategies use improved particle swarm optimization(PSO) algorithms to optimize the drive current, which limit particle generation and update through parametric equations to output target torque accurately, and try to further reduce copper loss by reducing particle dimensions and specifying coil combinations, respectively. The strategy comparison results show that the fixed excitation coils strategy can greatly reduce copper loss and avoid local hot spots on the premise of outputting the target torque.