To dramatically improve resolution in phase detection as compared with a conventional one by using a semi-fixed resistance type position sensor using a resistor.

In this fire power regulator, a rotating phase of an output shaft 31 is detected by attaching a semi-fixed resistance type phase sensor 4 to the output shaft 31. In this case, the phase sensor 4 has a certain non-detection range, and durability of the non-detection range is lower than that of other ranges. Hence, the non-detection range is allowed to be used only when the phase sensor is restored from a normal rotation-side end of a fire power regulation range to an original position so that frequency of use of the non-detection range is reduced.