What could cause a relay to burn out during use?
Relay burnout may have been caused by overcurrent, overvoltage, vibration, or short circuit.
(It does not mean that the relays burn continuously with flames, because flame-retardant materials are used for the relay components.)
Conditions under which burnout is likely to occur
In general, relay burnout is caused by abnormal heat generation around the contact and tends to occur under the following conditions:
- Contact vibration (ultra-frequent switching) causes continuous arcing and melting of the resin at and around the contacts.
Vibration may be caused by a decrease in the voltage applied to the coil or malfunction of sensors, switches, or microcontrollers that control ON/OFF of the relay coil.
- When the contact voltage exceeds the maximum value (rated), or due to surge voltage of the load, insulation failure can occur between the same polarity contacts or short circuit between different polarity contacts.
- Exceeding the maximum value (specified value) of the current to the contact circuit or a short-circuit current to the contact can cause burnout.
- Dust of consumed contact and/or carbon is deposited inside the relay when used beyond electrical durability, and insulation between the contacts of the same polarity or between the coil and the contact is deteriorated.
If caused by application of overvoltage and overcurrent to the coil
If an overvoltage or overcurrent is applied to the coil, the coil will break due to a layer short, and in general, there will be no burnout. (There may be only a trace of abnormal heating on the coil.)
Regarding to malfunction examples and countermeasure for relays, refer to The SOLUTIONS [General-purpose Relay Edition].
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