Are your continuously replacing solid state relays (SSRs) due to failure?

If the answer is yes, then it could be that the failure is being caused by exposure to high ambient temperatures in the control cabinet. ADM has the solution.

Solid state relays, or SSRs are electronic devices. As with all electronics their efficiency drops off at higher temperatures.

If you take a look at the data sheet for a Eurotherm Zelio solid state relay, you will see that it will have a stated ambient air temperature for operation. This is typically in the region of -30 ~ +80°C.

However, this doesn’t necessarily mean that the SSR will perform as you expect.

The following derating curve shows how the rated load current reduces as the ambient temperature increases.

Zelio SSM3A325DB Solid State Relay Derating Curve

In the above example for the Zelio SSM3A325BD, you can see that the maximum load current starts falling away once the ambient temperature exceeds 40°C.

You wouldn’t be able to use this solid state relay to its maximum rated current, if the temperature in the control cabinet rises above 40 degrees.

With the Zelio SSM1A455BD the maximum load current starts to derate after 25°C.

Zelio SM1A455BD Solid State Relay Derating Curve

The solution to this problem, is to mount the SSR onto a heat sink. This will carry any excess heat away from the solid state relay and reduce the likelihood of failure due to derating at higher ambient temperatures.

ADM can save you the hassle of buying a new SSR, looking for a suitable heatsink and fiddling about with heatsink compounds.

We stock a range of Eurotherm solid state relays, which are ready mounted on to a heat sink.

Our range includes three phase 25A (maximum size) and 50A single phase SSRs.

Please do not hesitate to contact ADM on 1300 236 467 if you would like any further information, or advice about installing solid state relays.