Construction Of Induction Motor - Electrical Engineering Gate

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Saturday, March 5, 2016

Construction Of Induction Motor

 Construction of induction motor

Like any other electrical motor
induction motor also have two main parts namely rotor and stator
v  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.

The stator of the induction motor consists of three main parts :
1.   Stator frame,
2.   Stator core,
3.   Stator winding or field winding.

  1. Stator Frame:
                 It is the outer most part of the three phase induction motor. Its main function is to support the stator core and the field winding. It acts as a covering and it provide protection and mechanical strength to all the inner parts of the induction motor. The frame is either made up of die cast or fabricated steel. The frame of  induction motor should be very strong and rigid as the air gap length of  induction motor is very small, otherwise rotor will not remain concentric with stator, which will give rise to unbalanced magnetic pull.

  1. Stator Core:
                  The main function of the stator core is to carry the alternating flux. In order to reduce the eddy current loss, the stator core is laminated. These laminated types of structure are made up of stamping which is about 0.4 to 0.5 mm thick. All the stamping are stamped together to form stator core, which is then housed in stator frame. The stamping is generally made up of silicon steel, which helps to reduce the hysteresis loss occurring in motor.

  1. Stator Winding or Field Winding:
                The slots on the periphery of stator core of the induction motor carries three phase windings. This three phase winding is supplied by three phase ac supply. The three phases of the winding are connected either in star or delta depending upon which type of starting method is used. The squirrel cage motor is mostly started by star – delta stater and hence the stator of squirrel cage motor is delta connected. The slip ring induction motor are started by inserting resistances so, the stator winding of slip ring induction motor can be connected either in star or delta. The winding wound on the stator of induction motor is also called field winding and when this winding is excited by three phase ac supply it produces a rotating magnetic field.

v  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  induction motor are further classified as
1.   Squirrel cage rotor,
2.   Slip ring rotor or wound rotor or phase wound rotor.

The other parts, which are required to complete the induction motor, are:

  1. Shaft for transmitting the torque to the load. This shaft is made up of steel.
  2. Bearings for supporting the rotating shaft.
  3. One of the problems with electrical motor is the production of heat during its rotation. In order to overcome this problem we need fan for cooling.
  4. For receiving external electrical connection Terminal box is needed.
  5. 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.