Diagram of Squirrel Cage Induction Generator (SCIG):
Explanation (Operation):- In this system multistage gearbox is used to obtain constant speed irrespective of wind speed. SCIG require reactive excitation power. The SCIG takes the reactive excitation power from a capacitor bank, connected across the stator terminals of the IG Rotor of SCIG is rotated at more than synchronous speed(i.e. low negative slip) to generate emf (to export power)with the help of wind power. Generated voltage is 690 V AC. So it must be step up to 33 KV to connect to power grid.
Explanation (Operation):- In this system gearbox is used to increase the speed of high speed shaft as per design. IG require reactive power for excitation. Rotor of SCIG is rotated at more than synchronous speed (i.e. low negative slip) in the variable range to generate emf with the help of wind power. It uses AC-DC-AC power converter (Rectifier, Inverter & Filter) to convert variable frequency, variable voltage output of the generator into the fixed frequency, fixed voltage output required for grid.