Current Transformer Tester - Need some guidance - Page 1
Forum section: electronics / projects

author: japasetelagoas
author_rank: Regular Contributor
timestamp: July 12, 2020, 06:47:37 pm
content: Hi everyone.I'm planning on building current clamp tester for my graduation project. We build hall effect current sensors on the company that I currently work at, recently we had issues with our quite rudimentary test rig. It's basically a short circuit that runs on a long wire that loops several times in order to reach the desired current, then we get our sensors and clamp them to such wire. Some of our beefiest sensors read up to 2000A.I guess the main question that I have is how do these companies manage to provide such high currents (2400A) on what seems to be a small footprint for their products.https://emsyst.com/portfolio/current-transformer-testers/I thought about using a VARIAC to control the current, an internal load and a coiled cable from which I would clamp the sensor to it. It would be good if I could manage to come up with a design that wouldnotneed to use a loop of cables considering that not all of our sensors are clamp types, which means that I would need to physically loop the wire around the sensor instead of just clamping it to the loop itself. We provide sensors that measure both AC and DC, making the project even more challenging.I'd really appreciate any suggestions, literature, tips, anything.Maybe I'm just trying something a bit too complex for a graduation project.

author: trobbins
author_rank: Frequent Contributor
timestamp: July 13, 2020, 02:19:31 am
content: Perhaps measurements are not continuous, so any source or reference shunt could operate only for short time slice, and hence something like a resistive shunt for 250 or 500A would be ok for a reference standard.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 13, 2020, 02:25:10 am
content: If the voltage drop is merely 1V, the power consumption is only a few hundred watts. Maybe even less if a class D amplifier is used to drive it, but if this is mains frequency we're talking about, the reactance of such a loop will be pretty small.I wonder what the average permeability of a Hall effect clamp probe is. That could actually increase the voltage drop fairly significantly.(Current transformers oppose the induced current, so don't increase the voltage drop much.)Tim

author: floobydust
author_rank: Super Contributor
timestamp: July 13, 2020, 02:36:45 am
content: Only not so smart people calibrate with 1 turn and full current going through, not practical really. Why not use 10-50T wound as an (air core) toroid, like Fluke 5500A cal fixture in pic.With 2,400A the compliance voltage is quite low, even 0.5VAC is plenty to overcome connection and wire resistance but I found things heat up and the current starts to drift.A Variac is not great for calibration because mains voltage is constantly moving around. If you want accuracy, then you'd need to use a programmable regulated AC power supply which is very expensive.

author: japasetelagoas
author_rank: Regular Contributor
timestamp: July 21, 2020, 02:30:18 pm
content: Quote from: floobydust on July 13, 2020, 02:36:45 amFloody, would you know what's the AWG of that copper wire? Tried searching on the 5500A/COIL manual but they don't mention it.Thanks.