| 摘要 |
<p>A mechanism prevents the start-up of a synchronous a.c. motor in other than a desired direction. The mechanism includes a flexible arm (30) having a finger (32) that will engage a radially projecting abutment (22) on the motor shaft. The finger blocks rotation of the shaft in a first direction and slides over the abutment when the shaft rotates in the opposite direction. A solenoid (36) moves the arm and finger out of the path of the abutment shortly after the motor is energized to allow the shaft to rotate in the first direction if the motor encounters an overload. Alternately, the arm may be formed of a bi-metal which is differentially heated by electrical current following motor energization to move the arm out of the path of the abutment.</p> |
