Solid State Relays vs. Electromagnetic Relays
Solid state relay (SSR) is a non-contact switch composed of solid-state electronic components, achieving the connecting and disconnecting circuits without contact and sparking based on the virtue of the electronic components (such as switching transistors, triacs and other semiconductor components). SSR is widely used in military, chemical industry as well as various industrial and civil electric control devices. The disadvantage is that SSR only has one group of contact pole thus overload capacity is poor. If the flowing current is beyond the rated current, it will break or even scrap. Electromechanical relays (EMR) are also commonly used in the industry. So what are the differences between solid state relays (SSR) and electromagnetic relays (EMR)?
| Items | Electromagnetic relay (EMR) | Solid state relay (SSR) |
| Structure | A magnetic switch made up of relay coils, movable elements, contact system etc., mechanical motion inside | An electronic switching device composed of thyristor, SCR, high-power transistor etc., no mechanical motion components inside, optically isolated between input and output |
| Working method | Control on-off state of circuits through electromagnet force based on the electromagnetic induction principle | Achieve isolation and relay switching on/off functions relying on electric, magnetic and optical characteristics of semiconductor devices and electronic components |
| Working status | Slow response, some noises, limited lifetime | Quick response, no noise, long lifespan |
| Operating environment | Not as good as SSR | Suitable for corrosion, moisture, dust, high altitude, electromagnetic interference and other harsh environments |
| Electrical performances | Simple drive, good isolation, good short-term overload tolerance, but large power consumption | No electric spark, no contact, fast switching speed with a small control signal to control high-current load |
In short, EMR and SSR have their advantages and disadvantages by comparison. Now the latter is more and more popular due to its reliability, non-contact, no spark, long life, no noise, no electromagnetic interference, high switching speed.
