Unless, you want to get the full insulation description from the
manufacturer and compare it to the transformer standard, you either have to
put your faith in what the manufacturer tells you (not something I would be
too keen about) or you may want to default to the lowest classification.
That could result in getting a new power supply depending on your needs. You
can ask for the conditions of acceptability and the test data, but you will
most likely only get the former. Check that and see if there is a
requirement for airflow over the power supply itself. Occasionally, the
supply manufactures will exceed the test temperatures and then tell the
testing agency to run some airflow over the power supply. That usually helps
them, but then you are required, as stated in the conditions of
acceptability, to run the same, or greater, airflow over the supply, not
just through the final box, but that amount over the supply itself.
Gary
-----Original Message-----
From: Zohar Zosmanovich [mailto:[email protected]]
Sent: Sunday, June 17, 2001 11:39 PM
To: 'Emc-Pstc (E-mail)
Subject: Transformer question
Hello,
I have a unit consist of metal enclosure and open frame AC/DC power supply,
approved to UL/IEC 950.
P.S includes PRI/SEC Transformer marked B/130 (Class B/130 deg.C).
During Heating Test, transformer winding temperature exceeds class A limits
(65 deg.C max. temperature rise). There is no mention about transformer
class in UL report (class of insulation system) or in TUV certificate (but
the power supply manufacture says it is class B).
What class should I consider this transformer to be?
Thanks
Zohar Zosmanovich
Compliance Engineer
RadWin (The Wireless Alternative) Ltd.
E-mail: [email protected]
RADWIN Ltd. 34 Habarzel St., Tel-Aviv 69710, Israel.
Tel.: 972-3-7666735 Fax.: 972-3-7657535
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