Performance analysis of a PMSM drive with torque and speed control

The paper presents performance analysis of a permanent magnet synchronous motor (PMSM) drive with torque and speed control. The PMSM motor requires sinusoidal stator currents to produce constant torque. The paper presents constituents for the mathematical analysis of the motor operation within the dq-axis model. The mathematical model serves as inspiration for development of a drive design based on the DSP processor and IGBT power module. The measurement system consists of a control unit equipped with an inverter and an encoder, the PMSM drive (500W; 5Nm; 800 rpm), a torque measuring device and a motor that work in the generator mode. The performance analysis has been performed in two control intervals. It is possible to operate the PMSM with the speed that exceeds the rated rpm if the permanent-magnet excitation is weakened by a demagnetising field component produced by the stator winding. However, it leads to a decrease of the motor efficiency. The conducted experiments have shown, that in the second control interval it is possible to increase the motor speed by about 30% as compared to the nominal rpm (overspeed).