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RE: OLTC Measuring Peak Current

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>I was wondering how I can measure the peak current.

Hi Adam,

As you probably know I love Rogowski coils and use them for all sorts of
current measurements now. They are easy to make, can't saturate because
they're air cored, and there is an equation that tells you what the
sensitivity will be, so you can get ballpark results without even
calibrating them.

IIRC the Rogowski coil equation is in a PDF document somewhere at

On a related note, I've designed a little op-amp circuit that connects to a
Rogowski coil or CT, and shows your *TC primary current on an analog meter
with a peak hold characteristic. I have got the attack time of the rectifier
down to about 5 microseconds and the decay time about 0.05 seconds, so it
reads the peak primary current within 10% as long as the burst length is at
least one cycle and the breakrate is at least 20bps (any less and the
pointer just jumps around)

I'm working on getting the attack even faster (to deal with half-cycle
peaks) and the decay even slower and I'll publish it when I'm done.

Steve C.