Thyristor Speed Control

IL„ary 1989 THYRISTOR SPEED CONTROL This low-cost circuit gives excellent speed and torque control of series motors rated up to 3500 W as used in electric drills, saws and grinding machines. Built from only seven components, the speed controller is suitable for fitting into a compact ABS enclosure with mains input and output. Electric tools with electronic speed con- trol are invariably more expensive than tools without this useful facility. If the purchase of several tools is considered, it is, therefore, a good idea to decide on the construction of a single speed control unit that can be used with all electric tools, including the ones already available. The thyristor speed control circuit is, of course, also suitable for loads other than electric tools. Intensity control of a nor- mal bulb, for instance, is possible when it is remembered that the maximum out- put power of the circuit is only half the nominal power consumption of the load. This is so because the circuit uses o...