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Solid State Relay Modules
November 2021

Throughout the history of electrical architecture for industry, relays have been a key technology that use simple on and off switching to control a high-power signal with a lower power source. For a long time, Electromechanical Relay (EMR) Switching was the go-to technology in virtually every industry that used control and power circuits for industrial control panel or outdoor field signals.

Yet, Electromechanical Relays had some limitations

If you have ever walked into a legacy electrical control room, the human discomfort is immediately apparent. Your ears would have been assaulted by a near constant mechanical ‘clicking’ or ‘ chatter’ sound that is hard to get accustomed to. The second thing, evident to those with sensitive noses, is a slightly burnt metallic smell in the air. Now, this is completely normal for industrial automation systems that use EMR switching.

The high clicking noise is caused by the mechanical moving parts in the EMRs that enable the output connection. The slightly burnt metallic-ether smell is the near constant internal ‘arcing’ that happens during each circuit movement.

Over time, it became obvious that Electromechanical Relays had a few challenges that needed to be overcome. These included: -

Uncomfortably high decibel levels during operation

- Contact point burnouts over time
- Physical movement limited the operating frequency
- Long turn-on and turn off time
- Chattering under inductive loads
- Vibration due to constantly moving mechanical parts

When put together, these challenges limited the use of EMRs in many applications. The need was felt for a different kind of switching technology, which could provide a better profile for industrial automation.

Here is where Connectwell Solid State Relays are a preferred solution
enChoosing a Relay Module based on application

While Electromechanical Relays (EMR) and Solid State Relays (SSR) are similar in many ways, the key difference is the working principle. Conventional EMRs have physical isolation between input and output. Connectwell Solid State Relays on the other hand, have optical isolation between input and output. Significantly, Connectwell Solid State Relays are purely electronic devices and have no mechanically moving parts. With this foundation, there are many benefits of using Connectwell Solid State Relays in industrial automation applications.

Whisper-quiet operations
Unlike EMRs, Connectwell Solid State Relays are ideal in low noise requirement applications like medical appliances where silent operation is a critical necessity.

Longer MTBF and life
Connectwell Solid State Relays have no mechanical movements. EMRs are subject to a constant contact ‘bounce’, which can cause a higher Mean Time Between Failure (MTBF) and shorter effective lifespan. This is why the life of Connectwell Solid State Relays are between 90 to 100 times longer than that of standard EMRs.

Higher switching speeds
The mechanical nature of EMRs limit the circuit speed due to the physical movement of contacts. Connectwell Solid State Relays employ semiconductor switching which makes switching far faster. Conventionally, the frequency of EMRs is 50 to 60 Hz, whereas the frequency of Connectwell Solid State Relays is 1.5 to 2 KHz.

Extreme responsiveness
Utilising semiconductor technology, and with no mechanical movement for contact, the On and Off switching time for Connectwell Solid State Relays is far less than that of EMRs. This is a productivity advantage in many critical processes which require speed of response.

Switching of inductive load.
Inductive load connections at the output of EMRs, cause chattering and arcing due to back EMF, which reduces relay lifespan. As Connectwell Solid State Relays are not susceptible to these electrical disturbance limitations, they are a preferred solution for applications with inductive loads.

Robust vibration and shock resistance
Connectwell Solid State Relays are also a preferred solution for demanding and high vibration environments, as the absence of mechanical moving parts ensures no drop-off in performance and efficiencies.

Better TCO profile
With their higher life, lower input and robust performance in demanding conditions, Connectwell Solid State Relays offer a far more attractive Total Cost of Ownership profile.


Connectwell Solid State Relays are a preferred choice where noiseless operations, high-performance, extended lifespan and robustness in high-vibration environments is a requisite.

These include applications such as:

For Isolation Applications

With the wide variety of control circuitry, often the control voltage and operating voltages are different. Here is where Relay Modules are used to isolate the voltage interface.

To know more about Connectwell Solid State Relays, specifications and areas of application in your industry,

For Solid State Relay Modules Click here
For Slim Solid State Relays Click here