Abstract: Adjustable Speed Drives (ASDs) are extensively used in commercial and industrial heating, ventilation, air conditioning and refrigeration (HVAC/R) equipment’s because of many advantages in control and energy savings. The ASDs use PWM inverter with high speed switching devices such as Insulated Gate Bipolar Transistors (IGBTs) generates the common mode voltage (Vcm). This Vcm causes the bearing voltage (Vb), which leads to premature bearing failure.In some industrial applications the PWM inverters and the motors are located separately thus requiring long motor cable. Which contributes over voltage and higher Vcm at the motor terminal due to the voltage reflection phenomenon. Higher the common mode voltage results in higher induced Vb. This paper presents modeling, simulation and analysis of bearing current, bearing voltage in PWM multilevel inverter fed induction motor of 5HP and 10HP Motors and THD Analysis of PWM MLI fed induction motor without long cable is done. Simulation is carried out using MATLAB Simulink.

Keywords: Adjustable speed drives (ASDs), Bearing voltage, Bearing voltage Ratio (BVR), Common mode voltage, Voltage reflection phenomena, Multilevel Inverter.