Patent ID: 7129672

Claim:
A controller apparatus for a synchronous motor, which has a stator wound with AC windings, a rotor installed within an inside of said stator, rotatably, and a lock function for holding a rotating position of said rotor with respect to said stator, therein, comprising: an inverter for supplying AC voltages having a predetermined voltage/frequency characteristic to the AC windings, which are wound around poles of the stator of said synchronous motor; and a controller portion for controlling said inverter, so that the AC voltages, being supplied from said inverter to the AC windings wound around the poles of the stator of said synchronous motor, is changed into DC voltages to be supplied thereto, when rotation of said rotor is zero (0) and also when a lock function signal is ON in condition thereof, wherein the DC voltages to be supplied from said inverter to the AC windings wound around the poles of the stator of said synchronous motor, when rotation of said rotor is zero (0) and also when the lock function signal is ON in condition thereof, are determined at a value so that current flowing through said AC winding therewith comes to be equal or less than a rated current thereof.