What is a Solid State Relay (SSR)?


A solid state relay (SSR) is an electronic component that switches power (current) to a load circuit and provides electrical isolation between an application's control circuit and load circuit. It is a competitive technology to electromechanical relays and other switching technologies.

Why Use Solid State Relays?

Long Life: Solid state relays have no moving parts. Therefore, there is no mechanical wear and tear on the output contacts. The typical life expectancy of a solid state relay may be more than 50 times that of an electromechanical relay. Ideal for repetitive applications.

Quiet Operation: Solid state relays make no acoustical noise when the output contacts change states. This is highly desirable in many commercial applications.

Minimum Electrical Noise: Zero voltage turn-on and zero current turn-off allows for minimum electrical disturbances generated by SSR.

Low Power Consumption: Solid state relays require very little power "coil current" to switch large loads.

Shock & Vibration Resistant: Solid state relays are not susceptible to erratic or unreliable operation when operating under tough environments.

Ideal for Harsh Environments: Solid state relays do not generate sparks or electric arcs, do not bounce either electrically or mechanically. Magnetic fields have little effect on SSR.

High Compatibility with Control Systems: DC controlled SSR can be switched ON and OFF by digital systems such as PLC and μC based systems and digital systems. AC controlled SSR can be driven by limit switches, thermal switches and sensors carrying AC control signals. Microcontroller based SSR allows for networking.

Fast Switching: Random turn-on solid state relays respond to a control signal in less than 100μs. Phase control and Burst control can be easily achieved to provide accurate AC power control.

Position Insensitive: Suitable for mounting in either vertical or horizontal position, "dead bug" position, adjacent mounting.

Solid State Relay Applications

Although there are literally thousands of individual uses for a solid state relay, most can be catagorized into the following applications:

Heating Control
This encompasses the largest segment of solid state relay customers. Applications include, but are not limited to: professional food equipments, plastic molding/extrusion machinery, HVAC&R, and soldering equipment.

Benefits: Temperature accuracy long life, no maintainance, safe product, easy to interface. Suitable for compressors soft-start, heater, fan, blower and valve control.

Lighting Control
These applications are usually broken down into three categories: theatrical, warehouse, and commercial. Many of these products used in this segment are designed for the specific application.

Benefits: Dimming, silent operation, fast switching, long life, no maintainance, safe product, easy to interface, reduced parts count.

Motion Control
Includes elevators, lifts, hoists, exercise equipment, conveyor systems, solenoid and valve control.

Benefits: Endurance, shock & vibration resistance, soft start, reversing, no arcing, fast switching, long life, no maintainance, easy to interface, reduced parts count.



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