FAQ02167 of General Purpose Relays FAQ

The following causes are probable.

1. Coil Layer Short

If overvoltage is applied to the coil, the coil's insulating film will be destroyed, and short-circuiting will cause high temperature. The color of the coil will change, and the resin around the coil will melt. It is also possible that an external surge was applied to the coil circuit, but this is often difficult to determine.

2. Contact Chattering

Abnormal heat is generated when there is contact chattering and arcing continues between contacts. If the fluctuation in the voltage applied to the coil is large, the cause may be that the Relay contacts are frequently switched.

3. Rated Load Capacity Exceeded

If, for example, the connected load exceeds the Relay's contact capacity or switching ability, arc heat will melt the contacts. If this occurs, the DC load conditions will be more stringent than the AC load conditions.