Question

A three-Phase synchronous motor has been provided
with damper winding. It can be started as a:
(1) Single-phase synchronous motor
(2) Three-phase squirrel cage induction motor
(3) Single-phase induction motor
(4) Three-phase alternator

Answer 1

Damper windings work essentially the same way squirrel cage rotor windings in induction motors work.

They consist of a cage of straight bars of copper or aluminum evenly spaced around the rotor in cylindrical pole machines or even spaced across each pole in salient pole machines. The bars are connected to end-rings which essentially short all bars together on each end forming a cage.

When magnetic lines of flux produced in the stator (armature) windings cut across the rotor bars, currents are induced in the cage.