Prediction of local instabilities caused by inverter dead time in AC drive

Abstract

Undesired low-frequency self-sustained speed oscillations are encountered in fan, compressor and pump drives utilizing open-loop frequency-controlled induction motor drives. Discontinuous rectifier current at light loads and the dead-time of the inverter switches are the main sources of such oscillations. This paper proposes a concise analytical method to predict the risk of self-sustained oscillations due to these two phenomena.