Design and Fabrication of Sensorless Vector Controlled Induction Motor Drive

Abstract

DC motors are popularly used for variable speed applications as they require simple power processing unit and simple control algorithm and offer good dynamic performance. But conventional DC motor has problems related to mechanical commutation, while induction motor has low cost, less maintenance requirement, very rugged and reliable. So now induction motor drives driven by voltage source inverters are replacing conventional DC motor drives in all variable speed applications.

There are various methods to control speed of induction motor viz. Stator Voltage control, Rotor resistance control & V/f control. The above mentioned methods give the speed control but have disadvantage of sluggish response. Advantage of vector control for AC machines has revolutionized the field of ac drive. It has solved lots of problems of scalar control method. Vector control gives the control of AC motor as a separately excited DC motor i.e. controlling the flux component and torque component of current individually. Vector control requires shaft mounted speed encoder for position sensing which is costly and has reliability issues. It is possible to sense speed signal from machine terminal voltages and currents using an ARM controller. Sensorless induction motor drives are popular because of their reliability and ability to be used in critical conditions.

Proposed project presents a digital implementation of speed estimation and closed loop vector control of induction motor drive with the use of ARM controller.