Generally speaking, relay contacts are made of copper or silver. If there is oxidation, polish the contacts with small sandpaper, and then pay attention to the fact that the relay cannot work in a humid environment for a long time, otherwise it will be oxidized.

When the moving and stationary contacts are not in contact with each other in the energized state, if the current of the disconnected circuit exceeds a certain value, or the voltage applied at both ends of the contact gap after disconnection exceeds a certain value, an arc will occur in the contact gap.

Extended data:

Arc is actually a discharge phenomenon of gas between contacts under the action of strong electric field, which produces high temperature, strong light and sparks. The existence of arc not only burns the metal surface of the contact, reduces the service life of the electrical appliance, but also prolongs the breaking time of the circuit, and even causes the relay contact to fail, which may lead to a fire or gas accident in serious cases.

Therefore, in order to accurately detect the change law of contact pressure, it is necessary to ensure that the current broken by the electromagnetic relay and the voltage applied at both ends of the relay contact cannot exceed the rated value during the experiment.

The main factors affecting arc ablation are: first, the characteristics of arc and its influence on electrode heat flow and arc force, and second, the response of contact material to arc heat and arc force.

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