Novel Current Control Assisted V/F Control Method for High Speed Induction Motor Drives

This paper deals with the starting problem of the conventional V/F control method in case of high speed induction motor using air bearings. The friction torque of air bearings changes according to the bearing state and the operating conditions. And also the initial friction torque is usually larger than that of the conventional bearings. So the starting failure sometimes occurs under the low bearing temperature in case of motor drives using the conventional V/F control based inverter. Therefore this paper suggests a new robust current control assisted V/F control method, which has the starting mode, the transition mode and the conventional V/F control mode. The robust starting mode adopts the current control assisted V/F control method to cope with the starting issues due to the unknown friction torque. And the transition mode provides the smooth voltage transition to the conventional V/F control mode to get the smooth current profile. The simulation and experimental results show the validity and the usefulness of the proposed method.