Introduction

Introduction

We have seen the various features of a three phase alternator. Similar to a d.c. generator it is a reversible machine. If a three phase supply is given to the stator of a three phase alternator, it can work as a motor. As it is driven at synchronous speed, it is called synchronous generator. So if alternator is run as a motor, it will rotate at a synchronous speed. Such a device which converts an electrical energy into a mechanical energy running at synchronous speed is called synchronous motor. Synchronous motor works only at synchronous speed and cannot work at a speed other than the synchronous speed. Its speed is constant irrespective of load, no doubt, its speed changes for an instant at the time of loading.

In this chapter, we will discuss how synchronous motor works and various features of three phase synchronous motor. Before beginning the study of the synchronous motor, it is necessary to study the production of rotating magnetic field. The rotating magnetic field (RMF) is very important to understand the working of synchronous motor.