ABSTRACT
The induction generator used in type 2 turbines is mostly the wound rotor (slip ring) generator. The rotor of this generator is connected to adjustable resistance through power electronic switching devices, one of these systems is shown in Figure 9.1. Each winding is connected to an external resistance r, with two solid-state switches in anti-parallel configuration in shunt with the resistance. When the switches are continuously closed, the resistances are shorted. When the full value of the resistances is needed, the switches are continuously open. If the value of the resistances needs to be adjusted, the duty ratio of the switches is regulated. To obtain a smooth operation, the switching frequency of the solid-state devices is set high (kHz range).
