4 ms·
My guess is that it is likely from Y caps filtering common-mode noise. They are great for filtering EMI to pass strict emissions regs, so it is easy to use them
by Workaccount2 2y ago
My guess is that it is likely from Y caps filtering common-mode noise. They are great for filtering EMI to pass strict emissions regs, so it is easy to use them liberally.
I'll admit I don't know what kind of currents they see, but 5mA on transients wouldn't be particularly surprising. There is also the factor of how sensitive the GFCI is.
- photon_rancher 2y agoOver 100nF of unbalanced Y-caps is needed at 60Hz/120V to see 5mA gnd current. That would be a big Y capacitor (2.2n or lower is common) and they’re usually used in a balanced configuration which would reduce it further. If a Y capacitor fails on one leg, you have a problem. If a Y capacitor fails is only present on one leg, you have a problem. And if it’s resistive leakage, that’s almost a watt of dissipation - also huge and probably a short in a cable and potentially a fire risk. 5mA is a massive threshold for well designed devices
- Workaccount2 2y agoIt would be fast transients that are in the kHz to MHz and over 120V. Thats why I wonder about the sensitivity of the GCFI. Can it tolerate 5mA for 50ns?
- atoav 2y agoIt should, typically trip times should be in the single digit miliseconds range (the idea is to stop within half of a 60/50Hz cycle).