| 摘要 |
PROBLEM TO BE SOLVED: To realize high reliability and compactness by positively performing shift from the start operation to synchronous operation by controlling an operation transfer switch from a star operation circuit to a synchronous operation switch, when the number of revolutions of a permanent magnet rotor reaches the number of synchronous revolutions relative to power supply frequency. SOLUTION: A microcomputer 22 controls each switching means of a start operation circuit 14 and performs start operation by suppressing the input at the inversion side relative to a non-inversion side by alternately switching the current direction of a rectifying current which flows into a coil A. Then when the number of revolutions of a permanent magnet rotor detected by an optical sensor 12 reaches the number of synchronous revolutions, first to fourth transistors 16 to 19 are turned off, so that TRIACs SW1, SW2 are turned on to transit to the synchronous operation circuit 21 for the control of shifting to the synchronous operation. By doing this, shift from the start-up operation to a synchronous operation can be performed positively with high reliability, high safety and accelerated miniaturization is also promoted. |
