Starting circuit for single phase async. motor - uses triac in series with auxiliary winding with coil of reed relay in principal winding to switch off triac when current is established

摘要

The circuit has a principal field winding, an auxiliary field winding, a series phase shifting capacitor, and a short circuited rotating winding. This has the coil (9) of a reed relay connected in the principal winding of the motor. The reed relay contacts (10) are connected between a DC source (15,16,17) and the trigger circuit of a controlled electronic switch (12) connected in the motor auxiliary winding. The reed relay (9) contacts (10) are connected to an integrating circuit (21,22) supplying a pulse generator circuit (23). The resulting pulse train is connected to the gate of a triac (12) to reliably switch the auxiliary winding (4). The reed relay is placed flat on a printed circuit board and the control winding is formed from wire hoops soldered into tracks on the board so the hoops are series connected. The circuit is used in conjunction with motor driven switchgear.