Multi-Physics Characteristics of PMSM for Compressor According to Driving Mode Considering PWM Frequency

Abstract

When pulse width modulation (PWM) technique is used for permanent magnet synchronous motors (PMSMs) for compressors, current harmonics in the carrier frequency domain are inevitably generated. These current harmonics not only affect losses in PMSM and drive, but also create harmonic components of the electromagnetic force, which causes noise/vibration. Since the amplitude and harmonic order of the current harmonics depend on the driving mode, the efficiency and noise are also affected by the driving mode. Therefore, this paper presents the comparison of the efficiency, noise, and vibration characteristics of compressor PMSM according to the driving mode. In particular, space vector PWM (SVPWM), discontinuous PWM (DPWM), and square-wave modes were analyzed. First, the characteristics of the experimental current waveform for each driving mode are analyzed, and the time and spatial orders of the electromagnetic force are calculated based on the Maxwell stress tensor method. Then, based on the derived electromagnetic force, the noise/vibration characteristics of PMSM are analyzed. The efficiencies of PMSM, driving, and total (PMSM+drive) were compared according to driving mode. It was confirmed that there is a trade-off relationship between efficiency and noise/vibration according to the driving modes. All results were analyzed using finite element analysis and experimentally verified using manufactured motor.