ESTIMATION OF SHAFT VOLTAGE AND COMMON MODE VOLTAGE IN PWM INVERTER FED THREE PHASE INDUCTION MOTOR
Application of modern inverter topologies allows high dynamic operation of the variable speed drives with savings in energy. However fast switching frequency and high dv/dt introduces disadvantages like common mode voltages and shaft voltages which results in bearing currents. The lubricating film in the bearing acts as a capacitor that charges due to the transition in common mode voltage. This capacitor provides a charging mechanism to build up rotor shaft voltage. If this shaft voltage exceeds threshold value breakdown of the film takes place which causes current spikes. This electrical breakdown of film causes mechanical damage to the bearing. Parasitic coupling model over a wide range of frequencies is used for evaluation of shaft voltage and common mode voltage. In this paper shaft voltages and common mode voltages with two and three level inverter has been evaluated and compared. This circuit model can be used to evaluate the effects of two and three level inverter on shaft voltage and common mode voltage using MATLAB Simulink. This document gives formatting instructions for authors preparing papers for publication in the Proceedings of an International Journal. The authors must follow the instructions given in the document for the papers to be published. You can use this document as both an instruction set and as a template into which you can type your own text.
R.K.Dhatrak, Dr.D.M.Deshpande, Dr.R.K.Nema