Chunhua brand vacuum cleaner electronic speed control circuit

The figure shows the electronic speed control circuit of the Chunhua brand upright vacuum cleaner. The circuit consists of the following 2 parts: (1) Phase shifting circuit. R1, RP, and C2 form a phase shift circuit. When the voltage VC2 across C2 reaches the turning voltage of the trigger diode VD, VD turns on, C2 discharges, and the triac VS control electrode flows through a pulse current and is triggered to conduct. By adjusting the potentiometer RP, the phase of the control pole pulse can be adjusted to change the conduction angle of VS, thereby adjusting the motor voltage and controlling the speed of M. (2) Surge voltage absorption circuit. The motor M, which is an inductive load, has a phase lag in the load current. During commutation, a higher surge voltage is generated across VS. R2 and C3 form a surge voltage absorption circuit. S is the manual switch, XP is the power plug, and L is the inductor coil.