The thyristor is an electronic element of the controlled diode type. Thyristors are semiconductor elements and have a non-linear volt-ampere characteristic with two stable states - low and high conductivity. They are basic elements in high-current electrical engineering and are used as a substitute for various contactors and relays in starting circuits, frequency regulators, rectifiers, motor starters, inverters, automatic devices. They have their greater speed in the working process and longer life because there are no commutating parts. The name thyristors comes from the combination of the names of two elements: thyratron and transistor.
Thyristors can be low-power, medium-power and powerful. Power thyristors are used as electronic switches to switch voltages on the order of 500V to 1000V and currents in the range 50A to 500A. It uses the quality of the thyristor to switch very high currents in the anode circuit through a very low power of the control signal. Thus, the thyristor switches circuits with high voltages and currents quickly and reliably.