Impact of Dead Time Effect on Common Mode Electromagnetic Interference in PMSM Drives

The pulse width modulation (PWM) technique has been widely applied in permanent magnet synchronous motor (PMSM) drives, which causes common mode (CM) electromagnetic interference (EMI) issue due to its higher frequency. And moreover, this issue will be intensified by the dead time area inserted into the control signal of the switching device (such as IGBT or MOSFET) in the power inverter. In this paper, the CM voltage/current has been analyzed with the considerations of the switching process of the MOSFET as well as the influence of the dead time effect. In order to reduce the CM voltage/current, a dead time compensation method is recommended, which can reduce the distortion of CM voltage/current and relieve the high-frequency (HF) CM EMI noise. According to experiment result, it can be figured out that the spectra of the CM current have been reduced by nearly 5.5 dB $\mu$A at the resonance frequency with an appropriate dead time compensation in PMSM drives.