PURPOSE: To reduce controlling electric power and perform stable control, by using a stationary exciter for controlling the output of a main electric generator and using a miniature electric generator as a rotary amplifier.

CONSTITUTION: The miniature electric generator 21 connected to an engin 1 is used as a rotary amplifier and te output of an exciting rectifier 26 is controlled to control the excitation of field coil 7 of the main electric generator 5. When the Diesel locomotive runs and the rotational frequency of the engine increases, the voltage of the miniarture electric generator rises. However, the rise in DC output voltage is suppressed by controlling the phase of a voltage and current controller 27, which is made of a rectifier circuit containing thyristors in order to limit the charging current for a battery 19. Therefore, a field controller 28 functions as a stationary exciter to perform stable excitation control