Question

Leakage flux in an induction motor is
1. Flux that leaks through the machine
2. Flux that links both stator and rotor windings
3. Flux that links the stator winding or the rotor winding but not both
4. None of these

Answer 1

Correct Answer - Option 3 : Flux that links the stator winding or the rotor winding but not both

Concept of Leakage Flux:

• The Leakage flux in an Induction motor is basically due to the air gap between the stator and rotor which links to either stator winding or rotor winding but not links to both windings.
• The presence of an air gap between the stator and rotor of an induction motor increases the reluctance of the magnetic circuit.
• Consequently, an induction motor draws a large magnetizing current (Im) to produce the required flux in the air gap. That is why the small air gap is preferred for the induction motor which helps to reduce the magnetizing current.
• Hence for any machine, we have to always try for less leakage flux and more linkage flux so that the machine becomes more efficient.

If the air gap of an induction motor is increased,

1. The permeability of the magnetic circuit will decrease
2. The magnetizing inductance of the motor will decrease
3. Leakage reactance will increase
4. Leakage flux will increase
5. The magnetizing current will increase
6. This will cause a poorer power factor at all loads