Abstract: Now dayís induction motors are broadly used for variable load application, because load on induction motor is not unceasing for each time and itís varying as per load requirement. So itís necessary to change the speed of induction motor as per load variation. Motor speed is directly proportional to the supply voltage and inversely proportional to the supply frequency. The ratio of voltage and frequency must be kept constant during speed control. For maintaining v/f ratio VFD method is used. In VFD pulse width modulation technology are used to control the speed motor. This aim is achieved by using ARM controller. By comparing another speed control methods, VFD method is predominant.

Keywords: unceasing, variable frequency drive, H bridge inverter, ARM controller, Keil, protieus.