Stator and rotor of a monoblock induction motor

• Stator and rotor are the most essential parts of an induction motor.

• The stator is the stationary part of a rotary system which provides the necessary magnetic field required to rotate the rotor.

• The rotor is the non-stationary part of a rotary electric motor, which rotates because the wires and magnetic field of the motor are arranged so that a torque is developed about the rotor's axis.

Stator

>A stator consists of two parts.

(i)Stator core (ii)Windings>The stator core comprises of

compressed stampings.>The stampings are either

made of silicon steel or mild steel.

• The stampings are compressed using an hydraulic press and are kept intact by using a metal strip.

• The stampings are designed in such a way that slots are left for winding.

• The stator windings are made of copper wires(insulated incase of open well type).

• The number of windings vary depending upon the power of motor.

• Bamboo sticks are placed in between the slots to prevent the dislocation of the windings from their slot.

• Also insulating sheets are kept in the slots to prevent current conduction between the windings.

Rotor

>The rotor consists of two main parts,

(i)Rotor core (ii)Shaft >The core is made of

stampings which are compressed initially after which they are die casted.

• The stampings of the rotor are different from that of the stator.

• Slits are cut on the surface of the compressed stampings which are later filled by die casting the component.

• Those slits filled by the molten metal(usually aluminium) are called skew lines.

• Skew lines are generally made to prevent magnetic lock.

• The ends of the shaft are supported by deep groove ball bearings to give support and to reduce friction while rotation.

• As a considerable amount of heat is generated during the rotor’s rotation, a cooling fan is attached to the shaft to reduce the effect of heat consequently(not required incase of open well).

Stator and Rotor Arrangement

• The stator and rotor should never be in contact. An air gap of at least 2-3 mm must be provided, which is achieved by fixing the rotor on both sides with the help of bearings.

• The rotor must be perfectly balanced or it may cause vibrations leading to the damage of the stator and ultimately the motor. So the rotor is checked for any imbalance and is balanced by addition of extra metal by welding.