Modeling, simulation and analysis of common mode voltage, bearing voltage and bearing current in PWM multilevel inverter fed induction motor with long cable

Abstract

Adjustable Speed Drives (ASDs) are extensively used in industrial Heating, Ventilation and Air Conditioning (HVAC) equipments. As they offers several advantages in control and energy efficiency. The ASDs use PWM inverter with high speed switching devices such as IGBTs generates the common mode voltage (Vcm). This Vcm causes the bearing voltage (Vb) and resulting bearing current (Ib), which shortens the bearing life. The Long motor cable applications causes over voltage and higher Vcm at the motor terminal due to the voltage reflection phenomenon. Higher the Vcm results in higher induced Vb and the Ib. In This paper, modeling, simulation and analysis of the Vcm, Vb and Ib in PWM Multi Level Inverter (MLI) fed Induction Motor (IM) with long cable is carried out. The inverters are feeding 5HP and 10 HP motors. Simulation is carried out using MATLAB simulink.