100 Turn Current Coil

[bAdbOb]

We calibrate a large number of high current clamp-on ammeters. We have a homemade 100 turn current coil, but it causes compliance faults in the 5725A when currents are applied above 8 AAC. Does anyone know if any company manufactures a 100 turn current coil?

[PurelyNonsense]

I'm not sure if there is but when you have an over compliance is it in AC or DC?

[silv3rstr3]

I know the 5520A has the option to turn Load Compensation on and that stops it from humming and tripping the calibrator.  Only happens using AC current.  Never tried using 5725 with a coil.

[PurelyNonsense]

If you don't have the 5520 with the load compensation, in AC you can ramp up the current slowly and it has worked for me. But that was on a 50 turn coil, not a 100 turn.

[bAdbOb]

Only happens on AAC function.

[PurelyNonsense]

Ok, next question, what is the gage of the coil? That can play a part too. I know that I've seen 14 Gage is good. If you think the gage is ok, then try slowly increasing the current to see if it will help.

[bAdbOb]

I think the wire gage is too small. I will also try slowly increasing the current to see if that works.

Thanks for the input!!!

[radhiabouras]

I know only the 50 turn fluke 5500A/coil

[Bryan]

2 Factors
1. Inductive Reactance (your coil)
2. Compliance Limits (Calibrator ACI specs)

Look at a picture of the Fluke 5500A Coil, you need that thing splayed out to push much current thru it, I suspect your coil looks more like a donut.

[briansalomon]

I agree. The calibrator compliance voltage limit is protecting the calibrator from being asked to produce more power than that circuit is designed to produce.

Here is a link to the 5500A/Coil instruction sheet which shows the limitations of the calibrator. (coil)

download.flukecal.com/pub/literature/5500coiliseng0800.pdf

[bAdbOb]

Thank you to all for your help!!!

[Hawaii596]

The key issue is foldback. Our main coils are the 5500A/COIL units from Fluke. They work so well because they have good spacing and a toroidal layout. The ones that are plain loop (shaped like a circle) tend to have worse foldback (overlapping fields from opposite sides of the coils creating a reverse potential against each other, and in turn, developing an impedance which causes overcompliance on the calibrator.

Good suggestions to slowly increase voltage, and, of course, using LF COMP on 5520A. 

I read in a GIDEP procedure somewhere, a number of years ago, how they recommend when you use a home made coil, to shape it toroidally (fanned out in a large arc), with diameter of each turn of about 8 inches, and using I think, AWG 12 transformer wire.

Personally, I would not use a 100 turn coil, but opt for a good quality 50 turn. We can get 1000 Amps DC, and close to that in AC at 60 Hz in a 5520A using the Fluke 5500A/COIL.  We own a few, and they are just the best, I think.

In the good old days, I used to make my own, and it was always an adventure trying to get one with just the right proportions for minimum of foldback.

My opinion is that the makeup of the coil (toroidal layout, size of each turn, and uniform spacing and shape) are at least as important as the gauge of the wire.

Just a few thoughts.

[Bryan]

50 probably is some kind of limit, we have the 5500A Coil and a couple others from Fluke, one is a 25 turn for up to 3000 Amp/turns, the other is 50 turns and good up to 6000 Amp/turns however it'll only fit flexible loop transformers.  We use a 52120A to source them, it's a beast.