Solidstate relay (SSR for short) is to package the light-controlled thyristor and light-emitting diode together, and ensure the electrical isolation between them. Just like the coil and contact in relay are isolated from each other, the thyristor circuit can be controlled by turning on and off the light-emitting tube, and its function is the same as that of ordinary electromagnetic relay. Solid-state relay not only has no mechanical movement, no contact, so there is no wear and spark in the process of making and breaking the circuit, but also isolates the weak current control signal from the strong current controlled circuit, which embodies the functions and advantages of the relay and overcomes the shortcomings of the relay.
Function of solid state relay
SSR solid-state relay is a new type of contactless switching device, which will not produce contacts and sparks in the process of turning on and off. The function of the solid-state relay is that it can not only strengthen the driving function as much as possible, but also has a powerful isolation function, and there are no mechanical contact parts in the switching process. Therefore, the solid-state relay not only has the same functions as the electromagnetic relay, but also has logic circuit compatibility, vibration resistance and mechanical impact resistance, unlimited installation position, good moisture-proof, mildew-proof and corrosion-proof performance, excellent explosion-proof and ozone pollution prevention performance, low input power, high sensitivity, low control power, good electromagnetic compatibility and so on.
SSR solid-state relay is a contactless switch composed of microelectronic circuits, discrete electronic devices and power electronic power devices. The classification of solid-state relays can be started from the following points: (1) From the perspective of application, solid-state relays can be divided into AC type and DC type; From the point of view of switching mode, solid-state relays can be divided into voltage zero-crossing conduction type and random conduction type; From the point of view of output switching elements, solid-state relays can be divided into bidirectional thyristor output type and unidirectional thyristor anti-parallel type; From the point of view of installation mode, solid-state relays can be divided into pin-insertion type for printed road boards and device type fixed on metal bottom boards; From the input point of view, solid state relays can be divided into constant current source type and series resistance current limiting type; From the point of view of trigger form, solid state relay can be divided into zero voltage type and phase modulation type.