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Increasing the Output of a Rogowski Coil without an Integrator

Rogowski coils are convenient, lightweight, and easy-to-install.  However, the output of a Rogowski coil is very low. For example, the RCT-1800-000, made by Magnelab, outputs 70 mV for every 1000A on the primary, when operating at 60 Hz.  If operating at 50 Hz the output is even lower, only 58.33 mV per 1000A.  Dent Rogowski coils are similar; they output 131 mV per 1000A at 60 Hz, and 109.2 mV per 1000A at 50 Hz.

Because the output is low, manufacturers add an integrator (which has to be powered separately), to amplify the signal to something more usable, such as 333 mV.  As hinted at, these integrators need to be powered; in addition, they can also add error to the overall measurement. So is it possible to increase the output voltage of a Rogowski coil without an integrator?  The emphatic answer is YES!

You can double the output of a Rogowski coil if you wrap the coil around the primary conductor twice.  Of course to do this you will need a Rogowski coil that’s very flexible (and long).  I’ve found that the Magnelab Rogowski coils work great for this.  Without too much trouble I was able to wrap an RCT-1800-000 around a small conductor twice.  Of course it’d be even easier to wrap the RCT-2400-000 or the RCT-3600-000 around the conductor twice (or more).  If you can wrap the conductor three times, you will receive triple the output, i.e. 210 mV at 1000A.  The output grows nice and linear even with additional wraps.  Thus, a double-wrapped Magnelab Rogowski coil would output 333 mV at about 2379 Amps on the primary.  A triple-wound Magnelab Rogowski coil would output 333 mV at 1586 Amps.

There’s another benefit by double or triple wrapping a Rogowski coil around a primary conductor; you are able to monitor lower currents.  For example, a Magnelab Rogowski coil is 1% accurate down to about 25A.  You can improve the accuracy at lower ranges with additional wrappings.  Double-wrapped, for example, you can achieve 1% accuracy down to about 12A.

I’ve checked with Measurlogic and they have confirmed that their meters can accommodate a higher output from a Rogowski coil.

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