Dear Sir,

Intuitively, I would suspect that any capacitance between the primary and secondary of a CR8348 would have minimal to no effect on the operation of the unit. These are designed for the main power frequencies of 50/60/400 Hz, and the impedance of an extremely small capacitance is itself a very large number when considering these frequencies. I have had extensive experience with radio frequency magnetic design, and in high frequency applications, indeed this capacitance can cause problems. In these cases, the primary and secondary are separated as far apart as possible.

As far as the “polarity” of the CT affecting its AC performance, I personally have never seen this. We have had some experience with Ferro-resonance that occurs in larger commercial and ANSI grade 5 amp secondary CTs, but never with the small high turns CTs such as the 8348. I can only suggest some possibilities that have affected performance of CTs in the past.

- On extremely low current measurement such as ground fault CTs, position of the wires within the hole can have an effect on the performance. Such low currents only partially magnetize the core, and one side of the core can possibly be closer coupled than the other side of the core.

- Resonance could be a possibility if core unbalance occurs from non-uniform winding and non-resistive forcing function. However, all CR Magnetics cores are uniformly wound - or so they are supposed to be! ;-)

- Ground loops in the application design. Many times I have seen applications where designers were unaware of leakage between reference grounds across the typically isolated transformer windings. This is a strong possibility as switching the polarity of the 2 pin connector would change the relative references from in phase to 180 out of phase.

We would be interested in reviewing any CR part that is experiencing this phenomena. A washer made high mu (u) material such as nickel-iron glued on the side of the CT can help focus the magnetic lines of force better in the core when trying to measure extremely low currents. Please also review your circuitry to insure no possible ground loop problems are occurring. Be cognizant of the various facility connections present at your location, and how they might affect grounding.

Please keep us posted here at CR Magnetics. We are always interested in a challenge!