Bidirectional thyristor speed regulating circuit

The motor M is connected in series with the bidirectional thyristor VS. If the conduction angle of VS is changed, the AC voltage value applied to both ends of the motor M can be changed to achieve stepless speed regulation in the range of 0 to 220V. Generally, the trigger circuit of a bidirectional thyristor is relatively complex and uses many components. As shown in the figure, only one potentiometer RP is used to achieve the purpose of speed regulation. This uses an "equipotential trigger circuit", that is, whether it is a positive trigger or a negative trigger, the potentials of the control electrode G and the cathode T2 are the same. This circuit can be used for dimming and speed regulation of electric fans, incandescent lamps or other household appliances.