The function of SCR in the circuit of health pot is to control current and voltage. Silicon controlled rectifier can be divided into spiral type, flat type and flat bottom type in appearance, and spiral type is widely used. Silicon controlled rectifier has three electrodes-anode (a), cathode (c) and control electrode (g). It has a four-layer structure, the die is composed of overlapping P-type conductor and N-type conductor, and has three PN junctions. When silicon controlled rectifier is applied, large anode current or voltage can be controlled by adding small current or voltage to the control electrode. Thyristors with current capacity of several hundred amperes or even several thousand amperes. Thyristors below 5 amps are called low-power thyristors, and those above 50 amps are called high-power thyristors.