Question

Explain the purpose of making two types of rotor construction for three-phase induction motors​

Answer 1

Answer:

The three phase induction motor is the most widely used electrical motor. Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, the absence of commutator and good speed regulation. In three phase induction motor, the power is transferred from stator to rotor winding through induction. The induction motor is also called a synchronous motor as it runs at a speed other than the synchronous speed.

3 Phase Induction Motor Construction

Like any other type of electrical motor induction motor, a 3 phase induction motor is constructed from two main parts, namely the rotor and stator:

Stator: As its name indicates stator is a stationary part of induction motor. A stator winding is placed in the stator of induction motor and the three phase supply is given to it.

Rotor: The rotor is a rotating part of induction motor. The rotor is connected to the mechanical load through the shaft.

The rotor of the three phase induction motor are further classified as

Squirrel cage rotor

Slip ring rotor or wound rotor or phase wound rotor.

Depending upon the type of rotor construction used the three phase induction motor are classified as:

Squirrel cage induction motor

Slip ring induction motor or wound induction motor or phase wound induction motor.

The construction of a stator for both of the kinds of three phase induction motors is identifcal, and is discussed briefly below. Please ensure you are using the appropriate electrical tools if you’re going to be deconstructing a motor yourself.

The other parts of a 3 phase induction motor are:

Shaft for transmitting the torque to the load. This shaft is made up of steel.

Bearings for supporting the rotating shaft.

One of the problems with electrical motor is the production of heat during its rotation. To overcome this problem, we need a fan for cooling.

For receiving external electrical connection Terminal box is needed.

There is a small distance between rotor and stator which usually varies from 0.4 mm to 4 mm. Such a distance is called air gap.