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# Minimum Arc Distance - ChemE needs some help from some EEs!

## Minimum Arc Distance - ChemE needs some help from some EEs!

(OP)
Hi - I apologize in advance in that I wasn't exactly sure in which forum to place this question.

Here is my scenario:

A 15 micron diameter tungsten wire will have 4700 Volts (DC) on it. The space between the wire and its surroundings is filled with clean plant air which is relatively humid – 60% rel humidity.

I have an ultrafine laser micrometer which I want to fixture around the wire as it passes from spool to spool (the wire conveys very smoothly so it doesn't bounce around at all) According to the drawing for the laser mic, I would have about 0.63 inches of clearance on each side of the wire.

Would this be enough gap to prevent an arcing event?

Your help will be greatly appreciated.

### RE: Minimum Arc Distance - ChemE needs some help from some EEs!

I believe you'll be OK for the voltage and dimensions involved.  Check out Peek's equation which is an experimentally derived equation.

The main components are:

Ec - m E0 d K

m - shape factor = 1 for smooth cylindrical conductor
E0 - 21.1 kV / cm
d - relative air density
K - for small conductors, K = 1

Compare the result of this to the actual voltage a gap spacing that you have.

This is a pretty conservative approach.  If corona isn't likely from the values involved, you won't get a flashover either.

Probably should have posted this under electrical/electronic engineering other topics.

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