An over temperature switch is installed in the generator. The switch contacts close when the stator windings reach a temperature of 210 degrees C and automatically reset when the temperature returns to a safe level. The output frequency of the generator is 400 Hz and is controlled by the GCU.
The PMG supplies electrical power to generator control unit (GCU). This power is used to control the generator circuit. The PMG has 3 phase windings in the drive part of the IDG. A voltage regulator supplies DC power to the stator windings of the exciter. In the rotating rotor a 3 phase voltage is generated and then rectified to DC by diodes. The rotating DC field, thus obtained, is used to control the 3 phase main generator; the output is supplied to the generator line contactor (GLC) and from there to the generator control unit. This output from the generator is used to control the voltage regulator, which now makes sure that the main output is 115 ± 2.5 V. the frequency controller uses the PMG voltage and makes sure that the generator operates at 12000 ± 120 rpm to obtain a frequency of 400 ± 4Hz.
The GCR is controlled by a logic circuit and is energized when the frequency is above 365 ± 2.5 Hz. When energized, voltage regulation starts. When voltage and frequency are correct the PRR is energized and the generator line contactor is energized through the action of the AC bus transfer system. When in operation, the GCU examines and continuously the generator system. To achieve this several protective functions are built into the GCU including;
The drive ensures that the generator only operates at a given rpm, irrespective of the engine rpm and generator load. The brushless AC generator produces the desired power. When the input shaft rpm increases or decreases the output frequency varies respectively. This variation is detected by the GCU. The GCU relays an electrical signal to a