Literature Review on Variable Frequency Drive for Induction Motor

ABSTRACT Variable Frequency Drive(VFD) varies frequency of the input power to motor hereby controlling the speed of the motor.AC voltage input is applied to bridge diode rectifiers that produces a dc output which is then given to the inverter section. The inverter section consists of PWM inverters using IGBT’s. PWM signals is the train of pulses with fixed magnitude and frequency and a varying pulse width. The output of the PWM inverter is given to the 3 Phase Induction Motor. VFD converts a fixed frequency, fixed voltage sine wave power to a variable frequency, variable output voltage used to regulate the speed of the induction motor. Most of the Voltage Source Inverters (VSI) uses pulse width modulation technique because the voltage and current waveform at the output is approximately a sine wave. VFD’s predominantly improves the efficiency and the performance of the induction motor. Speed of the motor is controlled with the help of VFD by keeping the Voltage to Frequency (V/Hz) ratio constant.