more inductor lies

A ground wire choke, the wire is thick to withstand 16A currents without interrupting the PE path. The extremely high inductance with so few turns give the high ur away, and that will saturate easily.

I was once bitten by this effect - during the EMC test it looked fine and we passed, but when real ground currents occurred the suppression was gone and we got too much noise. Had to put in a bigger choke, and retest and re-qualify. With some discussion and documentation we could fortunately avoid most of the re-qualification costs.

Arie de Muijnck

Yeah, and all three models have the same SRF? Don't worry... they're not available anyway.

Ground current limits, through common-mode and stray capacitances, are typically restricted to being 30 times smaller than this, at the power line frequency and it's lower multiples.

RL

Where was this choke located, w/r to any protective earth and what was the power rating of the component, or system?

RL

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The 16A (or 20A) rating allows for fault conditions and large surges while keeping series R low enough to pass PAT testing.

.... Phil

On 2019-09-12 03:03, legg wrote: Where was this choke located, w/r to any protective earth and what was

Data acquisition system in a factory, 16A choke in the PE of the mains connection to minimize RF noise entry from the mains. Unfortunately the customer used some I/O single ended and grounded the other end for safety (original spec said I/O was floating). The ground loop currents came from voltage drop over the mains installation PE wiring (heavy motors in the vicinity). The choke saturated and passed too much RF noise for the high sensitivity (differential) thermocouple input circuits.

Power rating? I guess that was about 50VA for the DAQ system. Mains fusing for our outlet was 16A, hence the choke rating.

Arie