HV wire

[timelessbeing]

I need to extend the leads between a tiny 300mA inverter board and a small CCFL (these are flatbed scanner components). The wire markings identify it as AWM 3239 3kV-DC 150°C VW-1 with silicone rubber insulation. It doesn't specify the wire gauge but it looks to be around 24AWG. Anyway, I don't want to buy special high-voltage wire for this. Can I substitute?

[alexanna]

Re: HV wire

I don’t know the answer about substituting wire,But ccflwarehouse dose sell small quantities of the HV and return wire.

[timelessbeing]

Re: HV wire

Thanks but it's not worth the shipping charge to me.

What distinguishes high voltage wire? Is it better insulation? If so, I can just add heat shrink tubing to ordinary wire.

[Th3_uN1Qu3]

Re: HV wire

What distinguishes high voltage wire? Is it better insulation?

Yes.

[Krankshaft]

Re: HV wire

HV wire insulation is usually made of thick molded silicone.

[delaware74b]

Re: HV wire

The supply side (typically pink) is rated for 3kV and is 24 AWG.

The return is rated for 300Vand is 28AWG.

This info comes straight from ccflwarehouse.com website.

[timelessbeing]

Re: HV wire

The colours of this one are grey and white.

[delaware74b]

Re: HV wire

White is the return wire.
The supply wire can be any color other than white. I've seen blue, black, gray, and pink.

I'm an electrician by trade and to quote my boss: "Electricity doesn't care what color wire it's in."

[Pyr0Beast]

Re: HV wire

Current in the wire is in range of 20mA

[timelessbeing]

Re: HV wire

Why is the thickness of the wires different. Isn't current the same for the whole circuit?

[Pyr0Beast]

Re: HV wire

More insulation on one wire.

[timelessbeing]

Re: HV wire

But wire gauge is the thickness of the conductor. I thought that insulation had its own rating system.

[Pyr0Beast]

Re: HV wire

No idea then.

Ground wire can possibly return all the fault current from other lamps as well or could be made to sustain more mechanical damage than the hot wire.

[Th3_uN1Qu3]

Re: HV wire

Only that the ground wire is the thinner one in this case. It's simply a case of insulation thickness - maybe someone was wrong when he said the HV wire is thicker gauge.

I'm not going to splice one apart to find out, but i believe the wire gauge is the same only insulation is thicker on the HV line.

[timelessbeing]

Re: HV wire

OK that makes sense now.

[timelessbeing]

Re: HV wire

Hi folks. Let me show you what NOT to do with high-voltage circuits. (see attached snapshots).

The white connector that you see attached to the outside of the black box goes to the CCFL (don't know exact voltage). It used to be soldered to the inverter board. I moved it to the outside of the box, and connected it to the board using some thick leads I chopped off some components. Then I surrounded the leads with hot glue.

In the 'after' pic you can see a black trail where electricity has arced through the hot glue. A separation of approximately 5mm. Evidently, hot glue is not a good insulator, and possibly, even worse than air. I'm pretty sure there is an air gap of roughly the same separation between the traces on the back of the board.

What do you guys think? Remove the glue and use as-is? Use something else as an insulator? Is the inverter fried and unusable now?

[timelessbeing]

Re: HV wire

HV wire insulation is usually made of thick molded silicone.

Maybe bathtub silicone would make a good insulator?

[yyonline]

Re: HV wire

Use something else as an insulator?

They make RTV162 and other specialty silicone potting materials specifically to be nonconducting. I'd recommend you look into one of those.

[Pyr0Beast]

Re: HV wire

Scrape the carbonised PCB off and don't use hot glue there.

[b700029]

Re: HV wire

The hot glue had some additives or other impurities (dirt, moisture, etc.) in it that lowered its dielectric strength. In their pure form, almost all the plastics have greater dielectric strength than air at normal atmospheric pressure.