Patent ID: 7888893

Claim:
A control apparatus for a synchronous motor comprising a PWM power converter for driving said synchronous motor, a brake for stopping and retaining a moving part of said synchronous motor, a brake drive unit for generating a drive signal for instructing said brake to apply or release, and pole position inference means for inferring a pole position of said synchronous motor, wherein said pole position inference means has timing control means for starting said inference process after instruction of brake release to said brake by said drive signal, wherein said pole position inference means has speed instruction means for generating a speed instruction of said moving part which is practically zero before starting said inference process and a speed controller for calculating a thrust instruction value from a relationship between said speed instruction and a speed detection value obtained from a movement distance signal of said moving part and controlling said power converter, and wherein said timing control means starts said inference process by said pole position inference means after generation of said drive signal for instructing said brake release in accordance with excess of said thrust instruction value over a predetermined value.