Single Phase Induction Motors – Introduction

The single phase induction motors are small motors. These motors have power rating in fractional horse power range. These motors are used in homes, offices, shops and factories. They provide motive power for fans, washing machines, hand tools like, drillers, record player, refrigerators, juice makers etc. The single phase motors are simple in construction. The main disadvantages of the motors are

1. Lack of starting torque
2. Reduced power factor
3. Low efficiency

Types of Single Phase Motors

There are three types of single phase motors. They are

1. Single phase induction motors.
2. Single phase synchronous motors.
3. Single phase series (or universal) motors.

Single Phase induction motors

The majority of single phase motors are of induction type. The power rating is in terms of fractional horse power. They are classified according to the starting methods, employed.

1. Resistance – start (split-phase)
2. Capacitor – start induction motor
3. Capacitor – run induction motor
4. Shaded pole induction motor

Single phase synchronous motor

These motors run at constant speed. They find applications in clocks and turn tables where a constant speed is required. There are two types of single-phase synchronous motor.

1. Reluctance type
2. Hysteresis type

Single phase series (or universal) motors

These motors can operate either in DC supply or in single phase AC supply. This type of motor can provide high starting torque and high speed. These motors are mainly used in kitchen equipment, portable tools and vacuum cleaners etc.

In the next topic, construction, operation, starting methods and various types of single phase induction motors are described.

Construction of Single Phase Induction Motor

The construction of a single phase induction motor is similar to three phase squirrel cage induction motor. The rotor is the same as that of a three-phase induction motor, but the stator has only a single phase distributed winding. Figure shows the construction of a single phase induction motor. It consists of two parts. One is stator and another one is rotor. The air gap between stator and rotor is uniform. There is no external connection between stator and rotor.

Single phase induction motor

From the principle of operation, the 1 – Φ induction motor has no self starting torque. This can be explained in two ways.

1. Two field (or) Double revolving field theory
2. Cross field theory

Read More Topics

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