Signal control device

A signal control device (10) controls the cycle of a three-phase signal used to control a three-phase high-voltage converter (22). The arithmetic unit (14) of the signal control device (10) determines the timing of the change cycle for each phase so that the cycle of the V phase or W phase signal is changed at the point when the phase difference between the U phase and the V phase or W phase reaches a prescribed phase difference after the cycle of the U phase signal is changed. A control unit (12) controls the changing of the signal cycle for each phase at the timing determined by the arithmetic unit (14).