Induction motor is a nearly constant speed motor. The necessity for a variable load operation often requires a control method to vary its speed, when other control method are used, the motor runs at full speed and the flow of the output is throttled, or damped. The influence of these methods results in increase in high inrush current and power consumption which result in increment in energy cost. To overcome this problem, this work presents a new concept of Variable Frequency Drive (VFD) for AC induction motor that uses PWM (Pulse width modulation) techniques with a six pulse signal on an inverter to feed the motor with a varying frequency to vary the speed. When a Variable Frequency Drive (V.F.D) was added to the motor driven system for a variable load operation it consumed only about 1.68% of inrush current, reduced power consumption by about 60%, thus, offer potential energy saving in a system in which the load vary with time. Therefore the objective of this design is realized. This project will serve as a useful guide for industry on energy management.
Keywords : Induction motor, Inrush current, Pulse width modulation, Variable Frequency Drive.