Patent ID: 8362730

Claim:
A synchronous machine starting device comprising: a power conversion unit for converting supplied power into AC power and supplying the AC power to an armature of a synchronous machine; an electric power line for supplying said AC power from said power conversion unit to said synchronous machine; an AC voltage detection unit for detecting AC voltage supplied to the armature of said synchronous machine through said electric power line; a rotor position detection unit for detecting a rotor position of said synchronous machine, based on the detected AC voltage; a power conversion control unit for controlling said power conversion unit, based on the detected rotor position, wherein said AC voltage detection unit has a first output end and a second output end isolated from said electric power line, transforms AC voltage supplied through said electric power line at a first ratio to output the transformed voltage from said first output end, and transforms AC voltage supplied through said electric power line at a second ratio and then limits the transformed voltage to a prescribed positive voltage value or lower and a prescribed negative voltage value or higher for output from said second output end; and a detected voltage selection unit for selecting one of the voltage received from said first output end and the voltage received from said second output end and outputting the selected one to said rotor position detection unit.