Question

Below stated are some of the statements about the squirrel cage induction motor. You need to identify which of the following is incorrect.

1. Very poor speed control

2. Although they are energy-efficient white at full load, they need a lot of energy while being started.

3. They are susceptible to voltage variations.

4. The induction motor consumes more current when supply voltage is reduced.

5. They are explosion-proof as there are no brushes which eliminate the risks of sparking.

1. 1, 2 & 3
2. Only 5
3. 2, 3 & 5
4. None

Answer 1

Correct Answer - Option 4 : None

Squirrel Cage Induction Motor:

• A 3 phase squirrel cage induction motor is a type of three-phase induction motor which functions based on the principle of electromagnetism.
• It is called a ‘squirrel cage’ motor because the rotor inside of it – known as a ‘squirrel cage rotor’ – looks like a squirrel cage.
• This rotor is a cylinder of steel laminations, with highly conductive metal (typically aluminum or copper) embedded into its surface.

 

Advantages:

• They are low cost
• Require less maintenance as there are no slip rings or brushes
• Good speed regulation as they are able to maintain a constant speed
• High efficiency in converting electrical energy to mechanical energy while running
• Have better heat regulation
• Small and lightweight
• Explosion-proof as there are no brushes which eliminates the risks of sparking.

 

Disadvantages:

• Very poor speed control.
• Although they are energy efficient while running at full load current, they consume a lot of energy on start-up.
• They are more sensitive to fluctuations in the supply voltage.
• When the supply voltage is reduced, the induction motor draws more current.
• During voltage surges, an increase in voltage saturates the magnetic components of the squirrel cage induction motor
• They have high starting current and poor starting torque (the starting current can be 5-9 times the full load current, the starting torque can be 1.5-2 times the full load torque)