Induction motor drives equipped with diode rectifier and small DC-link capacitance

This paper deals with sensorless vector-controlled induction motor drives that are fed by a frequency converter equipped with a diode front-end rectifier. A small dc-link capacitance is used, which makes it possible to replace the electrolytic capacitors with film capacitors. The natural frequency of the dc link is chosen considerably higher than six times the mains frequency but lower than the switching frequency. A recently proposed sensorless controller can be exploited; only minor modifications for small capacitances are needed. Simulation and experimental results of a 2.2-kW drive equipped with a capacitance or only 24 mu F demonstrate operation in a wide speed range.