Georg,
My representative from LGA America did a little research for me some time
ago about leakage current as associated with prEN50178. The research was on
the 1994 issue of the standard but it still applies in the 1995 issue.
The results are based on section 5.2.11.1 of the standard:
1) For pluggable (removable or modular line cord) equipment the limit is
3.5mA AC / 10 mA DC.
2) If the leakage current exceeds this level then there are three possible
ways of dealing with the problem. a) a duplicate PE conductor or an
automatic disconnect which monitors the continuity of the PE conductor or a
double-wound transformer. I believe the "double-wound transformer" is
referring to an isolation transformer in the primary circuit which actually
reduces leakage current. We have always used an auxiliary PE conductor
which is bonded to the rear of the chassis and the PE symbol is located at
both the conductors bonding points. When the second PE conductor is used a
note is required in the operating documents which requires the connection of
this conductor for proper installation (section 7.2.3.2).
3) For fixed installations there is effectively no limit to the amount of
leakage current allowed. See section 5.2.11.1 paragraph 4, "Measurement of
leakage current is required on EE which is not intended for permanent
connection". Conversely, for EE that is intended for permanent connection
(fixed wiring), the measurement is not required.
There was a letter written by LGA Nrnberg with instructions to this
effect. I do not readily have my copy but if you contact LGA in Nurnberg
and reference a letter written to Mr. Werner Pster of LGA America /
EuroConsult, Inc. They should be able to copy you with the information.
Also the letter was originated in German, if you want an English version I
believe Mr. Pster still has a translated copy. You reference myself and
reach him at:
Mr. Werner Pster / EuroConsult, Inc.
[email protected]
However he is a consultant and he may charge for his time.
As far as the status of the standard is concerned, I was told that even
though it is still in preliminary status, the standard has been released for
type testing. Once again you may validate this with LGA Nrnberg.
Hope this helps you.
Doug Powell
Advanced Energy Industries, Inc.
Ft. Collins, Colorado USA
[email protected]
----------
From: Georg M. Dancau
To: emc-pstc discussion group
Subject: Status of prEN50178
List-Post: [email protected]
Date: Tuesday, August 12, 1997 6:28AM
Hi compliance folks
Does anybody have information about the status of prEN50178.
This standard specifies some measures which must be taken if the leakage
greater than
3.5 mA (clause 5.2.11).
Best regards
George
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