Scenario

An installed relay burned out and no longer operates. It requires replacement, but the root cause of the burn-out needs to be identified and resolved first.

 

Issue

The most likely causes of a relay burning out are as follows.

1. Coil layer short circuit: If a voltage in excess of the coil's rating is applied, the insulating film on the coil may be degraded or destroyed, causing a short-circuit. This short-circuit will create excessive heat, which can melt the resin around the coil and effectively destroy the relay. It is possible that an external surge caused this overvoltage condition.
2. Contact Chattering: When rapid switching of the contacts occurs, it can generate arcing between contacts. With a large enough voltage, this can generate abnormal heat and result in damage to the coil, causing a short circuit and burn-out.
3. Exceeded the Rated Load Capacity: If a connected load exceeded the relay's contact capacity or switching ability, heat from arcing will melt the contacts.

 

Solution

In order, the resolution to the above issues are as follows.

1. Coil Layer Short Circuit: Check the applied voltage against the rating of the coil, and ensure that it is below the maximum rating. Install surge protection devices.
2. Contact Chattering: Assess whether rapid switching of contacts may have occurred, and take preventative measures in the devices that are causing that rapid switching.
3. Exceeded the Rated Load Capacity: Check the connected load against the rating of the coil. If the load is excessive, replace the relay with one with a higher rating, otherwise reduce the load.