Comparative Analysis of Electromagnetic Force Inverter Fed PMSM Drive Using Field Oriented Control (FOC) and Direct Torque Control (DTC)

Inverter-fed permanent magnet synchronous motor (PMSM) contains significant time-varying current harmonics in armature windings. These time-varying harmonics can change the distribution of the air-gap magnetic field of the motor, especially the current harmonics near the switching frequency of the inverter generate a high-speed rotating spatial harmonic magnetic field, which results a normal electromagnetic force wave with high-frequency and high-amplitude. The electromagnetic force wave causes severe vibration and noise of the motor. In this paper, the order and amplitude of current harmonics and radial electromagnetic force harmonics are obtained by analytical method and finite element method. Then we can draw the relationship between current harmonics and electromagnetic force harmonics and the distribution of electromagnetic force harmonics of permanent magnet synchronous motor under different control strategies is obtained. By comparison, we can choose the appropriate control strategy. Not only can verify the consistency of the analytical method and the finite element method, but also can be readily extended to study of the vibration and noise of the motor.