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Leakage current vs Hipot

Title: RE: Leakage current
The hipot test is for basic high voltage breakdown within the isolation transfomer and other isolation paths. This test is supposed to be done with the equipment OFF. This is how we did it for 10 years at Compaq. HiPot is performed with a high DC voltage. HiPot is done on every piece of product in the production phase.
The leakage current I speak of is tested with the equipment ON and is caused by capacitance between the AC primary front end and the isolated secondary.  Xc=1/2piFC in the transformer couples over the high voltage switching waveform of the primary front end and the current needs a return path. Operating leakage current is tested only once during the product safety testing for the agencies.
They are 2 different things.


-----Original Message-----
From: Rick Brooks [mailto:ribrooks@xxxxxxxxxxxxxxxxxx]
Sent: Wednesday, September 20, 2000 7:11 PM
To: Walker, Ed
Cc: IEEE 802.3 'DTE Power'
Subject: RE: Leakage current

I think that the issue you bring up is covered to some extent by the Hipot test that every 802.3 compliant port must pass.

The maximum leakage current that is acceptable in this test is higher than the numbers that you quote for medical.
Still it does guarantee that the DTE load current will return on the data cable.
The main power supply driving all the powered ports, if it is say an AC to DC type, must meet a different Hipot test
at the AC input.

I think that we should not form this DTE power spec to accommodate medical, it would be safer, but could add a lot of cost.

I believe that for non medical applications the SELV levels are sufficient. Isn't our situation exactly where SELV applies?

One worry that I have is that I've seen a few brand x,y,z  10/100 boxes that do not pass Hipot, but still work fine
from the users point of view.
Will DTE powered boxes that do not pass Hipot exist on the market in the future, and if so, will there be new safety concerns,

and user complaints?
Could be.

- Rick