Regulator

The voltage regulator limits the system voltage by controlling the rotor field current. While the field circuit is "ON," this regulator actually switches the field current on and off, at a fixed frequency of about 400 cycles per second, to help control radio noise. By varying the overall on/off time, the correct average field current for proper system voltage control is obtained. At high speeds, the on-time may be 10% and the off-time 90%. At low speeds with high electrical loads the on-off time may be 90% and 10% respectively.