KL-25 type thyristor automatic excitation device circuit

The circuit is shown in Figure 7-32. This excitation device is suitable for
automatically adjusting the excitation of synchronous generators with a terminal voltage of 400V and a capacity of less than 75kW .
  In the figure, SB is the starting button. When the generator is pulled to the rated speed by the prime mover, pressing SB for a short time will cause the generator
to self-excite and build up the voltage; RPi is the manual voltage regulating potentiometer, and RPi decreases ( or increase), the generator voltage decreases (or increases
). Adjust RP2 to adjust the sensitivity of the device. If oscillation occurs in the excitation , try lowering the sensitivity.
  When shutting down, the switch SA is cut off, and the trigger circuit loses power, and the generator can be demagnetized.