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FAQ02811 of General Purpose Relays FAQ

FAQ No. FAQ02811

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The clear relay case has turned black. Is there a problem?


Carbon and contact dust generated by the organic gas that results from arc discharge during load switching accumulates on the inside of the case. The discoloration is not a problem.

If using an inductive load, a surge suppressor can be introduced as a countermeasure against discoloration caused by arc discharge.

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