Open Ground question
Hi all, I have been having a problem with plugging into the shore power at our storage facility. They have all circuits run through GFCI outlets on the pole. When we plug in and we are not running any...
Forum Discussion
The neutral-ground detection in GFCI outlets has moved on from signal injection. At least some of the ICs now being used employ a second transformer around the hot and neutral wires. A downstream neutral-ground fault creates a coupling between the two transformers, creating a feedback path that allows an op-amp inside the IC to oscillate. When the oscillation amplitude crosses a defined threshold, the IC tells the solenoid to trip the latching contacts. The technique measures resistance, and the trip threshold is nominal 2 ohms, of which 0.6 ohms is officially allocated to the normal wiring resistance, and 1.4 ohms to the fault. UL 943 requires it to work correctly with a circuit load ranging from zero to the rated load of the GFCI.
