Relay Contact Arcing Phenomenon

Thread Starter

Surya1234

Joined Apr 23, 2021
16
Greetings Readers/Viewers,

I am trying to figure out if arc will produce across relay contacts as they open under different scenarios. I appreciate if you can give me your feedback on whether my understanding about the arc formation is correct or not for the following scenarios:

1. The device is carrying an 80A current. A user pushed the "OFF" switch and the microcontroller2 sends off command to the individual drivers. So the current reduces drastically as the loads are OFF. Microcontroller-1 de-energizes the relay.

My understanding- the arc will not be produced or will be very negligible as the load current is very small (idle microcontroller not driving any loads carries a small current)

2. The device is carrying 80A current. A user pushed "OFF" switch and the microcontroller2 sends off command to individual drivers. So current reduces drastically as the loads are OFF. The user disconnects the inline connectors so it interrupts the current flowing through the closed relay. Microcontroller-1 then de-energizes the relay.

My understanding- the arc will not be produced as the relay is not carrying any current at the time its contacts open.
 

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MaxHeadRoom

Joined Jul 18, 2013
23,906
The should be no, or little arc if no current is flowing, any arc that may occur is much greater when switching an inductive device, also when switch large DC currents, especially inductive, a plasma arc can occur and current can flow continously across the arc, in these cases, arc blow out features are used such as magnet blow out fitted near the contacts.
 
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