Modelling, Simulation and Experimental Analysis of Transient Terminal Overvoltage in PWM-Inverter fed Induction Motors

The PWM Inverters are widely used in electric power system to accomplish speed control of motors in various process industries, power station auxiliaries, etc. The usage of fast switching devices like IGBT PWM Inverters has led to the failure of many motors in different field of applications. This has aroused interest to study the impact of these PWM Inverters on the performance of induction motors. In the recent past many authors have presented their investigations on various issues associated with the motor failure due to over-voltage that appears at the motor terminals due to the impedance mismatch between the power cable and the motor as well as non-uniform distribution of voltage in stator winding. This paper describes the modeling of the system consist of PWM Inverter, Cable, induction motor and their interaction. The system is simulated in MATLAB and experimental study is carried out for validating the modeling and simulation of the drive system. Also frequency responses the motor is obtained to identify the surge impedance of the motor. At the end Sensitivity analysis is made to study the influence of system parameters Viz cable length, motor rating and rise time on motor terminal overvoltage. Finally simulated are compared with experimental results and found to be in good agreement.