The stator and rotor are the two main parts of an induction motor. The stator, which is stationary, contains windings that produce a magnetic field to turn the rotor. The rotor, which rotates, is made of stampings and a shaft and contains skew lines that are filled with molten metal to prevent magnetic locking. An air gap of 2-3 mm must be provided between the stator and rotor to prevent contact, and the rotor is balanced to avoid vibrations damaging the motor.

1. Stator and rotor of a monoblock
induction motor

2. • 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.

3. 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.

4. • 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).

5. • 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.

6. 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.

7. • 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.

8. • 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).

9. Stator and Rotor Arrangement

10. • 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.