Three-phase AC solid-state relay (hereinafter referred to as three-phase SSR) is a collection of three single-phase AC solid-state relays, and uses a single input terminal to directly switch the three-phase load, which can easily control three-phase AC motors, heaters, etc. Three-phase load. The three-phase common type SSR uses three triacs as the output switch contacts of the A, B, and C three-phases. The current levels are 10A, 25A, 40A, and the voltage levels are 380V and 480V. The model is SSR- 3-380Dccc and SSR-3-480Dccc; the three-phase enhanced SSR is based on three sets of anti-parallel one-way SCRs as the output switch contacts of A, B, C three-phase, current levels are 15A, 35A, 55A, 75A , 120A, 150A, voltage levels are divided into two series, 380V and 480V, the models are SSR-3H380Dccc and SSR-3H480Dccc.