BigPatents India

The Invention relates to a New Four-stage Power Controller for the operation of three-phase Induction Machines, worked either as motors or Wind-driven Grid-connected Induction Generators. This controller is meant for changing the stator connection from parallel delta to parallel star or series delta or series star, when the power output of the machine varies from full-load to no-load. With this operation the supply current waveforms of the machine remain sinusoidal, without harmonics in all the stator connections. Compared to operating the machine with a fixed stator connection, the operation with the proposed controller would result in (i) reduced kWh and kV ARh taken by the induction motor from the supply, on a daily basis. (ii) increased kWh supplied to the grid and reduced kV ARh drawn from the grid by the wind-driven induction generator annually. (iii) reduced kV A rating for power factor improvement capacitors, for both motors and generators. (iv) reduced starting current for motor or generator, when started in series delta or star connection.