# Induction Motor

## Speed Control of an Induction Motor

There is a various method of speed control of an Induction Motor. The rotor speed of an induction motor is given by the equation shown below. From equation (1) it is clear that the motor speed can be changed by a change in frequency f, a number of poles P, and slip s. Any one or …

## Pole Changing Method

Pole Changing Method is one of the main methods of the speed control of an induction motor. This method of controlling the speed by pole changing is used mainly for cage motor only because the cage rotor automatically develops a number of poles, which is equal to the poles of the stator winding. The number …

## Double Cage Rotor of an Induction Motor

A Double Cage Induction motor is that type of motor in which a double cage or two rotor windings or cages are used. This arrangement is used for obtaining high starting torque at a low value of starting current. The stator of a double cage rotor of an induction motor is the same as that …

## Cogging in Induction Motor

The phenomenon of Magnetic Locking between the stator and the rotor teeth is called Cogging or Teeth Locking. Even after applying full voltage to the stator winding, the rotor of a 3 phase induction motor fails to start. This condition arises when the number of stator and rotor slots are either equal or have an …

## Deep Bar Rotor

The Deep Bar Rotor in an induction motor is used to obtain high rotor resistance at starting and low rotor resistance at the running condition. The figure below shows a deep bar cage rotor with deep and narrow bars: A bar may be assumed to be made up of a number of narrow layers connected …

## Blocked Rotor Test of an Induction Motor

The Blocked Rotor Test of an induction motor is similar to the short circuit test of a transformer. In this test, the shaft of the motor is locked so that it cannot move and the rotor winding is short-circuited. In the slip ring motor, the rotor winding is short-circuited through the slip rings. In the …

## No Load Test of an Induction Motor

No Load Test is an indirect method used for determining the efficiency and also to determine the circuit parameters of the equivalent circuit of the three-phase induction motors. The open-circuit test is performed on the transformer. The no-load test is the same as the open-circuit test performed on the transformer. In this method, the motor …

## Starting of an Induction Motor

A three-phase Induction Motor is Self Starting. When the supply is connected to the stator of a three-phase induction motor, a rotating magnetic field is produced, and the rotor begins rotating and the induction motor starts. At the time of starting, the motor slip is unity, and the starting current is very large. The purpose …

## Autotransformer Starter

An Autotransformer Starter is suitable for both star and delta connected motors. In this method, the starting current is limited by using a three-phase autotransformer to reduce the initial stator applied voltage. The figure below shows the motor with the autotransformer starter: It is provided with a number of tappings. The starter is connected to …

## Star Delta Starter

The Star Delta Starter is a very common type of starter and is used extensively as compared to the other type of starting methods of the induction motor. A star delta is used for a cage motor designed to run normally on the delta-connected stator winding. The connection of a three-phase induction motor with a …