Speed Control and Braking of Three-Phase IM

This paper presents the simulation method to control the speed of three phase induction motor by v/f method and its braking. As we know Induction motors are the most widely used electrical motor due to the reliability, cheaper cost and thew therefore its controlling is also very important so the simulation model for speed control in close loop and for DC Dynamic braking is shown here. Out of the several methods of speed control of an induction such as change of number of poles, variation in frequency, variable stator voltage, constant V/f control, variable rotor resistance, slip recovery method etc., the closed loop constant V/f speed control method is most widely used. Pulse width modulated inverter is the basic requirement of the scheme. Here first a PWM Inverter is modeled and its outputs is fed to the Induction Motor drives. A MATLAB SIMULINK MODEL was designed to successfully implement a MATLAB model for Closed-Loop V/f Control on a PWM-Inverter fed 3-phase Induction Motor. It was noticed that using a Closed-Loop scheme with a Proportional Integral gave a superior way of controlling the speed of an Induction motor. In case of DC dynamic braking the AC supply is disconnected and DC is connected at a fix time and waveform is observed.