Overview of Solid State Relays
Technology always keeps changing. Earlier there were transistors that led to the use of television in every home. Later the electromagnetic relay came that produced high current and found use numerous operations. Today, there are solid state relays that work on a microprocessor. Solid State Relays have no moving parts. The electromagnetic relay had springs, magnetic field, and mechanical contacts. The SSR has properties of a solid-state semiconductor both optical and electrical. It performs the input to output isolation by using the semiconductor. It performs switching functions very well. There is much more to it and not just changing, that gives it an extensive scope in the future.
It is somewhat similar to the electromagnetic relays as well. For instance, SSR also provides total electrical isolation like it happens in an electromagnetic relay. It provides resistance to some infinite value when nonconduction or the circuit is open. On the other hand, when the circuit is closed, it has negligible resistance producing high current. It has the capability of getting designed as an AC or DC switch both. It uses TRIAN, SCR or switching transistor to make it happen. It is different from the mechanical contacts that were used earlier in a relay.
Fundamentally, there are no differences between an SSR and electromagnetic relay. The main advantage SSR has over the traditional relays is that it operates without the use of any moving part. Hence, the name a solid state relay. There are no issues of contacts get detached from each other due to moving parts. There is no chance of wear and tear happening as only solid parts are present in its construction. The On and OFF function takes places much faster as the chance of contacts get bounced up is very less.
There are no electrical noises produced due to the turn-off and turn on in case of zero current state and zero voltage state respectively. Elimination of electrical sounds is a great relief at times. Therefore SSR is gaining popularity slowly over the electromagnetic relays. One can buy it in its standard form that is an off the shelf pack that has ranges of few amperes of volts to several hundreds of amperes and volts. The output switching capability can be customized or bought in its standard form depending on your requirement. There are plenty of options as there are different current and voltage ranges available in the market.
Companies are making SSR make sure customers have plenty of options in the standard product itself. The operation of SSR is similar to that of the electromagnetic relay where even a small voltage input can result in very high voltage output. SSR takes less room than an electromagnetic relay and is much faster in operation. An SSR can operate by creating an Opto coupling instead of using magnetic fields for providing isolation. The type of switching device used decides whether the output of SSR will be AC or DC. Its functioning could be understood very well by referring to its diagrams. However, the fundamental principle is not hard to understand and can be learned quickly if you operate one.
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