This figure shows the basic control circuit for SCRs that use SBS triggers, and is preferable to that of Fig. 8-24 (triac), where high power must be handled, or whore rapidly rising voltages are encountered (high dv/dt,). Although the circuits of both Figs. 8-24 and 8-25 were designed as incandescent-lamp dimmers, the circuits are well suited to control of universal and shaded-pole motors. Such motors have higher torque at low speeds when open-loop controlled by these circuits, rather than with rheostats or variable transformers (because of the higher voltage pulses applied).
Required Field 
