Contact Gap in VCB

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How about that for leadership?

It depends on the construction of the VCB as it varies from manufacturer to manufacturer and can even vary between product groups. I know one company that uses magnetic fields.

More information can be found in the manufacturer's literature or through contact with the manufacturer directly, although some information may be proprietary and hence unavailable (patent protected or a trade secret).

Depends upon manufacturer to manufacturer.

Gap is necessary mainly to withstand impulse voltage between opened contacts.

This is highly dependant on the contact material itself, which is proprietary from one manufacturer to another.

Indeed, for a given gap , impulse voltage withstand drops significantly after the following cycle :

• close on short circuit ,and local microweldings of the contacts.
• open on no load ,and mechanically break the microwelds and creates spikes.

The characteristics of the spikes vary with the contact material ability to weld, and the way it behaves when breaking the welds.

By the way, this is one of the differences between a good VCB and a cheap one ...