Exciting control device of synchromotor

An excitation controller for a synchronous machine includes: a voltage detector for detecting an output terminal voltage of the synchronous machine connected to a transmission system through a transformer; a current detector for detecting a current outputted by the synchronous machine; a module type HSVC apparatus for operating arithmetically a reactive current value on the basis of output from the voltage detector and the current detector, operating arithmetically a high side voltage value from the reactive current value thus arithmetically operated and a reactance of the transformer and outputting a correction signal based on a deviation between the high side voltage value thus arithmetically operated and a voltage setting value; an automatic voltage regulator, having a voltage setter, for outputting a command which is obtained by adding the correction signal to a voltage setting value provided by the voltage setter; and an exciter for carrying out field control of the synchronous machine on the basis of the command issued from the automatic voltage regulator.