| 摘要 |
<p>A device for imparting an oscillating movement (e.g. for a bell) has an AC-fed motor with a control system comprising two optical or magnetic sensors for position, direction and speed inputting to a microprocessor, connected to two reversing relays for the motor. The motor is three-phase, and two phases each have a static thyristor relay and a reversing relay. There is a relay in the third phase which is always opened at the instant when the reversing relays in the other phases come into operation, thereby eliminating inductive voltages at the terminals of the static relays which would otherwise cause sparking at the reversing relay terminals. The coils of the reversing relays are in series. ADVANTAGE- No arcing at terminals of relays.</p> |
