Hi Charles:
> a) Does anyone one know the genesis
> of the requirement to lift the Neutral
> AND the Ground simultaneously
> during a leakage current test??
> (I am referring to UL6500)
While I am not familiar with UL 6500 per se,
I believe I can comment on the "lift" of the
neutral.
In times past, non-polarized products used a
single-pole power switch. Since the products
were non-polarized, the single-pole power
switch could be in the neutral rather than in
the phase conductor. When the switch is in
the neutral and is open, the leakage current
essentially doubles compared to the value when
the switch is closed (assuming the switch is
ahead of the line filter). (Draw the circuit
and you can readily see why the leakage current
doubles.)
Certainly, leakage current should be measured
(and controlled) for both the "ON" and "OFF"
positions of a power switch, especially a
single-pole power switch.
> b) What human body model is appropriate
> for UL6500? Can I use the one in UL1950??
Since you are referencing UL standards, the
"correct" measuring circuit (i.e, "human
model") is the ANSI circuit (C39.5?).
In practice, just use an ordinary ammeter.
This will give you a slightly (~5%) pessimistic
measurement. So, unless you are very close to
the leakage current limit, you need not use the
"humand body" model for leakage current
measurements.
For more details on both these questions, see
my article in the Product Safety Newsletter,
Volume 7, Number 1, January-February 1994.
You can download a pdf version of this PSN:
http://www.ewh.ieee.org/soc/emcs/pstc/psn/
The file name is:
94v07n1.pdf
Best regards,
Rich
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