If an induction machine is run at above synchronous speed, it acts as

If an induction machine is run at above synchronous speed, it acts as

Right Answer is:

Induction Generator

SOLUTION

  • If an induction motor runs at above synchronous speed with a supply connected to it, it works as an Induction generator.
  • To run an induction machine as the generator it slips must be less than zero that is negative slip (-1 < S < 0) it is also called the regenerative action of an induction motor.
  • In generator operation, a prime mover (turbine or engine) drives the rotor above the synchronous speed therefore for generator
    Nr >> Ns
    S =
     Ns  Nr/Ns
  • The supply here works simply as an exciter of the machine and instead of supplying any electrical energy, it receives electric energy generated from the machine.
  • When the speed of the induction motor is increased above its rated speed, the e.m.f and slip of current frequency will develop in the rotor winding but with the opposite direction as compared to the direction when it’s operating below synchronous speed.
  • The torque slip characteristics of motoring and generating action is given below

Scroll to Top