AC and DC HiPot Tester

[eskim]

Dear All,

What is the based difference between AC and DC HiPot tester. When I test HV equipment e.g. Surge arrester, cable, generator winding, etc. What is the best method using ac or dc tester ?

Some one told me that mA is the "most important" to select DC or AC ? I didn't understand what does it mean.

Thank you.
Eskim

 

[analogkid2digitalman]

It's been a long time since I've worked in hi-pot testing.

But I believe AC hi-pot testers are to test for insulation breakdown. The applied voltage is typically a few times the operating voltage (I think there are standards as to how much and for how long a time period, based on the type of equipment). The tester is current limited for safer operation. It trips an alarm when the pre-set leakage current is exceeded. For example, a 120VAC motorized power tool may have 600VAC applied for 1 minute and the current trip point set to a couple mA. The nature of the peak sinewave voltage actually 'stresses' the insulation.

DC based testers measure insulation resistance, I think. Never have used one.

Sure that there are many web sites out there that can provide a more thorough and accurate description of these testers.

Wheels within wheels / In a spiral array
A pattern so grand / And complex
Time after time / We lose sight of the way
Our causes can't see / Their effects.

 

[buzzp]

This subject is widely discussed on the web. Do a search but for starters here is a link to get you going.

http://www.compwest.com/library.htm

 

[buzzp]

One more link (probably better info than the last link)

http://www.ecmweb.com/ops/electric_putting_hipot_pasture/

 

[sreid]

We use Hi-Pot testers from Associated Research.

http://www.asresearch.com/

UL allows DC testing at a higher voltage if there is too much capacitive feed through to pass the AC test.