Thyristor controller for universal motor - provides selective speed control or fixed voltage operation using potentiometer connected to moving contact of selector switch

摘要

The modified circuit uses the same control element for setting the trigger angle for preselected fixed phase control of the thyristor and for selecting setting for speed control. The control element (12), pref. a potentiometer, is connected with one terminal to a pole of the supply, and with the other to a moving contact of a selector switch (14). A trimming resistor (17) may be connected in parallel with the controller (12). In one position the selector switch (14) connects the controller (12) directly into the charging circuit for the capacitor (13) providing the gate power for the thyristor. In the other position the controller operates on the speed regulator circuit.