SOLUTION

A punch press is a type of machine press used to cut holes in the material. Punch press-driven machines impose pulsating loads or require frequent starting of the motor. For such type of Machine, Class D Motor is best suited.

Class D Squirrel-Cage Induction Motor:

It is characterized by high starting torque, high starting current, high operating slip, inefficient operation efficiency for continuous loads, common applications are characterized by an intermittent load such as a punch press.

Note:- The best-suited motor for press and punches is cumulative compound Motor are Wound rotor and squirrel-cage motors

The punch presses (MN) are equipped with wound-rotor induction motors. These motors operate on the same rotating magnetic field principle as a squirrel-cage induction motor.

The wound-rotor induction motor exhibits the highest amount of starting torque per ampere of starting current of any 3-phase motor. The torque reaches the maximum when the rotor and stator currents are in phase with each other. Adding resistance to the rotor circuit causes the rotor current to be more in phase with the stator current, thus producing a greater amount of starting torque.