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My experience while working for Compaq reminds me that HiPot is tested on computers with the power supply not operating.
A high voltage positive DC potential is applied to BOTH AC inputs on the primary and the negative return is connected to the common ground (user touchable). The leakage current is measured from + to -.
In this case HiPot should be conducted on the sides of the line that do not have active components on them, namely the return lines. You are basically testing the insulation in the isolation transformers so the inputs can be connected to each other and outputs can be connected to each other. Since the test voltage is applied common mode the actual power devices see no potential.
Analog Product Specialist
Texas Instruments Inc.
7001 Weston Parkway
Cary, North Carolina 27513
From: R karam [mailto:rkaram@xxxxxxxxx]
Sent: Thursday, August 10, 2000 12:05 PM
To: Rick Brooks; stds-802-3-pwrviamdi@xxxxxxxx
Subject: More details...
I would have to revisit the PTC specs at this point, but on to the "active"
current limit, we will find that a hand full of analog houses have the process
and the expertise to deliver parts that can take the transients on and survive.
the good news is these parts do exist.
Since I am new to the standards, and the purpose I guess, is for us is to spec
a current limit in this case, we would have to guarantee ahead that an implementation
exist, yet not force any implementation. at this point it will be crowded around the
RJ45 to do the job properly. Until the volumes get higher and better alternatives are
Are we set on meeting the 2000v high potential spec for 802.3 when the connection is
live? (POWER IS ON) I heard that PBX's do not meet high-pot requirements- Arlan?
and may be someone from LUCENT can comment?
and if the active current limit is set to 350ma when the connection is live how does that factor into the high pot
breakdown?. I think we have been staying away from the isolation requirements, but if we
are talking current limits, then reality now sets in and we must face the details.
Come to think of it, how would the 2000v High pot be tested when the connection is live?
Currently we test high-pot with the board off NO POWER, and thank's to the magnetic the isolation
across it is NOT in question.