Motor control-speed

An induction motor can be controlled by using various methods either it is closed loop or open loop. There are many techniques of controlling the speed either by varying the slip by changing rotor resistance or terminal voltage and varying synchronous speed by changing number of poles or supply frequency. Changing of input frequency is more reliable as it is applicable to all induction motors. The speed of the motor can be controlled by using the pulse width modulation (PWM) method. This paper is mainly about the open-loop speed control method for a single phase induction motor. An open loop controller which is also known as the non-feedback controller is a type of controller that computes its input into a system using only the current state and its model of the system. The control scheme is based on the constant volts per hertz (V/f) method. To verify the functionality of the controller, a full working prototype is built. The prototype consists of an IGBT Full-Bridge Inverter, a motor and an analog controller with PWM. By varying the frequency fed into the PWM unit, the speed of the motor can be controlled. The speed of the motor increased steadily based on the frequency supplied by the control signal until it reached the desired speed and remained constant at the speed