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Subject: Re: UL Leakage Current Test - disconnecting Y-capacitors?
Date: Thu, 16 Jan 2003 10:36:16 -0500
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Depends to what UL spec you test. For the medical spec you can not
Our equipment is tested to UL3101-1 and it is permissable to to a hipot /
leakage test with the equivalent DC voltage.
The DC test voltage is eqivalent to AC volts (rms) X 1.414 and hold for 60
seconds. Often the voltage has to be ramped up to avoid tripping out the
leakage detector. Leakage linit is 1ma.
This was given to us by the testing agency that does our CE and UL
The leakage test should be made with power switch on and both line terminals
shorted together and tied to the HV tester. The return is connected to the
The X capacitors (Line to Neutral) and Y capacitors (line to ground and
neutral to ground) are for conducted EMI reduction. Often these are combined
with a common mode filter.
For correct response address, remove one after boppie
"Klaus Kragelund" wrote in message
> I'm performing an UL leakage-current test. The test is conducted by
> removing the ground wire and connecting a amp-meter from the chassis
> (instrument ground) to either mains wire.
> This is fine - but what puzzles me is that our Q department says it is
> ok to remove any Y capacitors during that test. Anybody know the
> rationale behind that? If I were to build an instrument with many
> Y-capacitors in parallel the current drawn by these will be high and
> possible lethal if the ground wire was removed....
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