Solid State Relay Applications, Advantages over Normal Relay


Solid State Relay Applications, Advantages over Normal Relay

Hey, in this article we are going to discuss about the Solid State Relay which is mostly known as SSR. Here we will discuss the applications of Solid State Relay, what are the amazing advantages of solid-state relay over a normal electromagnetic relay. SSR not have only advantages it also has some disadvantages and limitations we will discuss, so let's start.


What is Solid State Relay(SSR)?


Solid State Relay or SSR is a static semiconductor switching device that provides the same function as a conventional relay or electromagnetic relay means to switch the electrical power.

SSR has not any Moving mechanical contact mechanism inside it. SSR mainly constructed with an Infrared LED(which takes input supply) and phototransistor connected with MOSFET or Thyristors(these controls output).

It is an electrically operated switching device, it gets turns on when an electrical supply (generally 3 to 32 volts DC) applied to its input and gets turned off when the power supply removed.


What is Electromagnetic Relay(EMR)?


Electromagnetic Relay or EMR also an electrically operated switching device that works on the principle of electromagnetic attraction. It also used to switch electrical power.

If we see the construction of a normal relay, there is an electromagnetic coil, and there some moving and fixed iron or copper strips. During the operation, those strips contact each other and switch the electrical power. To get more knowledge about electromagnetic relay read the article, Relay Function


Difference between Solid State Relay and Electromagnetic Relay


The main differences between SSR and EMR are,

1. EMR works on the principle of electromagnetic attraction whereas SSR works on the principle of Photoconduction or optical coupling.

2. EMR has a mechanical movement contact mechanism in its construction whereas SSR is a static device having no moving contacts.

3. EMR is an Electromechanical device whereas SSR is a static semiconductor device.


Solid State Relay Advantages over Electromagnetic Relay


Actually, the main objective of using any relay is to control or switch a large amount of current, voltage, power using low current or voltage, so both SSR and EMR provides the same function. In fact, both of them provide isolation between the input and output circuit. But there were so many advantages of SSR over an EMR,

1. Solid State Relay or SSR can handle more current and voltage than an electromagnetic relay.

2. Solid State Relay provides very faster switching than an electromagnetic relay, for this reason, SSR is most suitable for pulse signal, digital signals, so it can be used with microprocessors, PLC, etc.

3. One of the biggest advantages of SSR than an EMR is, it provides a zero-current turn-off switching facility in case AC supply.

That means when we use an SSR for the switching of AC supply, it only got turned off when current goes to zero, this helps to eliminate ARC, load distortion and producing of back emf in case of inductive loads.

4. Most of the time electromagnetic relay shows a latching problem when it operates with high current, but in the case of SSR there is no metal strip, it is a static device so it does not shows any latching problem.

5. An SSR can be operated with a very low current and voltage as its input connected with a single infrared LED only. An SSR can be operated at a minimum of 3V DC with a few milliampere currents.

But an electromagnetic relay needs more current and voltage to be operated because its input connected with an electromagnetic coil which takes more current than a LED to perform properly. An electromagnetic relay can be operated perfectly at a minimum of 5V DC.

For this reason, SSR can be used with small sensors, transducers because they produce very low current as output.

6. As solid-state relays have no mechanical parts, so they have a larger life span, higher reliability, and smooth operation.

7. There is no noise, surges happen in Solid State Realy but in the case of the electromagnetic relay, reverse surge happens when the input signal is removed from the relay.

8. When an EMR is using with inductive loads, back current, noise, surge, etc happens but in the case of SSR nothing back current, noise occurs.

9. As SSR is a static device, so there is nothing operating sound occurs, but in an EMR contact sound occur.


Solid State Relay Disadvantage and Limitation


Although Solid State Relays have so many advantages but their drawback also there,

1. SSRs are so much costly than a normal relay or EMR, for this reason, EMR only most usable device nowadays also.

2. Almost all the electromagnetic relays provide both NO and NC function simultaneously but most of the SSRs are provide only one function either NO or NC. In fact, NC SSRs also very rarely available in the market.

3. SSRs are solid-state semiconductor devices so it produces so much heat during operation, extra heatsink arrangement is required.

4. SSRs are not suitable for high impedance circuits.

5. There is leakage current occurs in the SSR when it is in the off condition, but there is no leakage current occurs in the EMR.

6. SSRs are cannot provide linear voltage-current characteristics as there is transient occurs during operation.

7. It offers high resistance in its output circuit than a normal electromagnetic relay.


Solid State Relay Applications and Uses


1. The main application of SSR is to switch the high amount of AC power using low power DC signal.

2. SSRsare used for automatic heater control in baking ovens.

3. SSRs are used in the hydraulic system with the electronic control mechanism.

4. SSRs are used in Lift circuits, automatic sliding door circuits.

5. SSRs are used for motor control using PLC, microprocessors, etc.


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Solid State Relay Applications, Advantages over Normal Relay Solid State Relay Applications, Advantages over Normal Relay Reviewed by ETechnoG on 10/23/2020 Rating: 5
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