SKEWED by some angle.The rotor is not connected electrically to the supply but has current induced in it by transformer action from the stator.Most of the 3-phase induction motors use squirrel cage rotors because of their simple and robust construction ENABLING them to operate in the most adverse circumstances.It SUFFERS from the disadvantage of a low starting torque. It is because the rotor bars are permanently short-circuited and it is not possible to add any external resistance to the rotor circuit to have a large starting torque. Slip Ring Rotor or Wound rotor:It consists of a laminated cylindrical core and carries a 3-phase star-connected winding.The open ends of the rotor winding are brought out and joined to three INSULATED slip rings mounted on the rotor shaft with one brush RESTING on each slip ring.The three brushes are connected to a 3-phase star-connected resistance by slip ring as shown.At starting, the external resistances can be added to the rotor circuit to give a large starting torque.These resistances are gradually reduced to zero as the motor runs up to speed.The external resistances are used during starting period only.When the motor attains normal speed, the three brushes are short-circuited so that the wound rotor runs like a squirrel cage rotor.