What you got is exactly as stated in their specification.
http://www.tripplite.com/products/product.cfm?productID=228
----- Original Message -----
From: <j...@aol.com>
To: <emc-p...@majordomo.ieee.org>
Sent: Thursday, August 29, 2002 10:21 PM
Subject: Curious about Tripp-Lite "isolation transformer"
>
> Hello All:
>
> Some of the laboratory tests that I perform require a source of AC mains
> power that is fully isolated from earth. To provide this function, I made
a
> catalog purchase of a Tripp-Lite model IS-1000 "isolation transformer."
This
> unit is equipped with a grounded (3-prong) 120 VRMS plug on the AC mains
cord
> used on the input side, and has a 3-prong AC mains socket on the isolated
> side.
>
> When the unit arrived, I was surprised to find that the green-wire ground
on
> the input side was carried across to the ground pin on the AC socket of
the
> "isolated" side. Furthermore, one side of the 120 VRMS socket on the
output
> side was also tied to the green wire ground. In other words, the output
of
> the unit is not isolated from ground, even if I use a "cheater adapter" to
> break the connection of the ground pin on the output socket.
>
> I also noted that the unit has capacitors and what appears to be a large
MOV
> placed across the "isolated" output.
>
> My theory is that this type of isolation transformer is intended to
provide
> protection from transients or noise on the AC mains. However, I can't see
> what protection the transformer provides, except maybe from common mode
> transients on the AC mains pair. Even so, I am having difficulty
> visualizing any scenario where a common mode surge would appear on the AC
> mains pair but not on the ground wire (given that in North America, one
side
> of the AC mains pair is tied to ground at the service entrance).
>
> Is it possible that the transformer is designed with frequency-dependent
> coupling so that frequencies above 60 Hz do not couple well? Such a
scheme
> would provide some degree of protection from differential noise.
>
> I am wondering if any of you are familiar with this type of "isolation
> transformer" and the applications where someone might need such a device.
On
> the surface, I can't see what "isolation" benefit the transformer is
> providing when it is wired this way.
>
> It is relatively easy for me to modify the wiring to provide the fully
> floating, balanced AC output that I was seeking in the first place. The
only
> thing I haven't decided yet is whether to leave the capacitors and MOV
> connected across the isolated output.
>
> If any of you are familiar with this type of "isolation transformer" and
can
> explain the intended function, I would be interested to learn about it.
> Also, if you see any flaws in my rewiring plan, please let me know. I'm a
> little bit uneasy modifying a design that I don't fully understand.
>
>
>
> Joe Randolph
> Telecom Design Consultant
> Randolph Telecom, Inc.
> 781-721-2848
> http://www.randolph-telecom.com
>
>
> -------------------------------------------
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
>
> To cancel your subscription, send mail to:
> majord...@ieee.org
> with the single line:
> unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
> Ron Pickard: emc-p...@hypercom.com
> Dave Heald: davehe...@attbi.com
>
> For policy questions, send mail to:
> Richard Nute: ri...@ieee.org
> Jim Bacher: j.bac...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
> http://ieeepstc.mindcruiser.com/
> Click on "browse" and then "emc-pstc mailing list"
>
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
majord...@ieee.org
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Ron Pickard: emc-p...@hypercom.com
Dave Heald: davehe...@attbi.com
For policy questions, send mail to:
Richard Nute: ri...@ieee.org
Jim Bacher: j.bac...@ieee.org
All emc-pstc postings are archived and searchable on the web at:
http://ieeepstc.mindcruiser.com/
Click on "browse" and then "emc-pstc mailing list"
