Abstract: Induction motor for many years has been regarded as the workhorse in industrial applications. An induction motor can run only at its rated speed when it is connected directly to the main supply. However many application need variable speed operations. With the invention of variable voltage variable frequency drives (VVVF), the use of an induction motor has increased. Variable voltage variable frequency control provides a simple and cost efficient  method for open-loop speed control of  three  phase induction motor. This technique is popularly known as V/f control. In this paper principle and operation of V/f drive is summarized. This paper  include experimental results of Voltage, Current and Speed on different frequencies which shows that induction motor speed is vary according to frequency input and simultaneously supply voltage is controlled to maintain V/f  ratio constant.


Keywords: Induction motor, PWM, V/f Control, Duty Cycle Variation