PURPOSE: To improve the reliability of a doubling exciter doubling the main unit of an automatic voltage regulator, and effectively combining a demagnetization priority circuit and a magnetization priority circuit.

CONSTITUTION: Two manual voltage setters 28-1, 28-2 which are interlocked with an induction voltage regulator are provided. Interface modules 70-1, 70-2 associate two demagnetization priority circuit for amplifying the manual voltage setter outputs. Firing pulse control cards 110-1, 110-2 associate two demagnetization priority circuit for inputting the signals of the modules 70-1, 70-2 and an AVR signal. Firing pulse generation cards 160-1, 160-2 and power units 200-1, 200-2 associate magnetization priority circuit. Thus, an exciting system which normally operates even if the inner section is damaged or malfunctioned can be obtained.