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Frequently Asked Questions

Solid-state Relay Topic: Main Causes and Solutions of SSR Failures

 

FAQ No. FAQ02150

 

Question

What are the main causes of SSR failure and what can be done about it?



Answer

Large Load Inrush Current:
Motors, lamps, and other loads with a large inrush current will cause the output elements to be damaged if the inrush current resistance value of the SSR is exceeded.

Consider using an SSR with larger capacity.


1. Counter-electromotive Force from Load :


Output elements may be damaged if there is a large counter-electromotive force using valves, solenoids, and other inductive loads. Provide an element that absorbs counter-electromotive force.

2. Failure due to External Surge:

External surges may cause sudden damage to input and output elements. Load short circuit may also cause failure.

For safety, use a circuit that turns OFF the load if there is an abnormality with the SSR by using a contactor or breaker installed on the load power supply side. As a countermeasure against overcurrent, it is recommended to add a quick-burning fuse in parallel with the load.

3. Installation Environments

Output elements may be damaged if the ambient operating temperature exceeds the specified value. Take heat dissipation into account when installing the SSR, such as by not obstructing the airflow to the heat sinks. The SSR may be damaged by heat generated when the power is ON if the screws are not tightened sufficiently or the SSR is used with incomplete soldering. Wire and solder correctly.

 

 

Other Solid-state Relay FAQs

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 What is the difference between triacs and thyristors?

 The SSR does not turn OFF. What is causing this and what can be done about it?