SPEED CONTROL OF A THREE PHASE INDUCTION MOTOR USING PWM INVERTER

1 Post-Graduate Student (M.E. Power System), 2 Assistant Professor, 3 Associate Professor Department of Electrical Engineering, Government Engineering College, Bhuj, India jatinpatel_ee@yahoo.in,amkubavat@rediffmail.com,jhl_mahipal@yahoo.co.in ______________________________________________________________________________________ Abstract— There are different method of speed control of three phase induction motor and to control the speed of three phase induction motor generally using V/F control strategy. Out of the a number of methods of speed control of an induction such as pole changing, frequency variation, variable rotor resistance, variable stator voltage, constant V/f control, slip recovery method etc., the constant V/f speed control method is the majority generally used. In this method, the V/f ratio is kept constant which in turn maintains the magnetizing flux constant so that the maximum torque remains unchanged. Thus, the motor is totally utilized in this method. This paper include with simulation of V/F speed control of three-phase induction motor using PWM inverter strategy. The simulation work proves the idea of V/F control using PWM inverter and the software used for simulation is PSIM (Powersim).The performance of the volt per hertz strategy were evaluated through simulation shown in results. In constant V/F control, by use PWM inverter, we can vary the supply voltage as well as the supply frequency such that the V/F ratio remains constant so that the flux remains constant too. So, we can get different operating zone for various speeds and torques and also we can get different synchronous speed with almost same maximum torque. Thus the motor is fully utilized and also we have a good variety of speed control. It is effortless, cost-effective to easier to design in open loop. But the drawbacks of open loop is it doesn’t correct the change in output also it doesn’t reach the steady state quickly.