[R-390] thanks

[2002tii]

Richard wrote:

>Again, ignoring the R390 and its outrageous capacitive leakage current to
>the chassis, but looking at more sensible appliances with their expecation
>of being handled and mishandled by the general population... Hmmm.  Lessee,
>If I put a 1,000 ohm resistor on there and I still read (number picked out
>of the air) 10 volts then I would be leaking 10mA to ground - now I am going
>to get interested and so should any functional GFI since, AFAIR, a GFI
>should trip at 5mA.  Have I got that wrong?

AFAIK, the US National Electrical Code specifies that household GFI 
devices must trip within 25 mS with a current imbalance of 4-6 mA 
(nominally 5 mA), just as you recall.  There are also industrial-use 
GFIs that trip at higher current imbalances, and I believe European 
household GFIs may also trip at a significantly higher current 
imbalance than 5 mA.

And yes, there are lots of stray paths -- particularly, capacitive 
paths -- from the mains voltage to chassis in many 
electric/electronic devices, even if there is no RFI filtering 
connected to the chassis.  Power transformers have capacitive 
coupling from the windings to their frames (which are generally 
connected galvanically to the chassis), etc.  But the R-390A line 
filter causes ground current many orders of magnitude greater than 
these stray leakage paths, and several orders of magnitude greater 
than typical RFI-filtered appliances.

Best regards,

Don