why slip ring induction motor used in crane

 As the aim of the crane is to lift the heavy load with the help of rope or chains, so load demands a high starting torque. at the starting time, the crane motor demands a very large amount of current. which are not suitable for safety purposes. Therefore Squirrel cage induction motor is not used in cranes. because of starting torque of the squirrel cage induction motor too low due to the low resistance of the squirrel cage induction motor.

On the different scenarios with a slip ring induction motor, it looks like a normal squirrel cage induction motor. but the main difference is the construction of the rotor winding. slip ring induction motor rotor winding is connected with slip ring with the help of carbon brushes. the second end of the slip ring is connected with a high value of variable resistance. at the starting time increased the high value of variable resistance. so that starting torque becomes so high. and starting current drawn motor too lower. when motor speed becomes 90% then slowly decreased the variable resistance. this extra resistance provides high torque in the slip ring induction motor. so that slip ring induction motor suitable for cranes.

keypoints:-

why slip ring induction motor used in crane:-

1. slip ring induction motor starting so torque high.

2.slip ring induction motor drawn a low value of starting current.

3. flexibility of increased or decrease torque by adding the variable resistance.

4. main difference construction of rotor winding.