Ron,

You will probably have a hard time finding a converter suitable for this
application. Most medical devices are either (if low current draw) battery
operated or use a medical grade line-frequency transformer. In the latter
case they will also use a medical grade (low leakage) line cord. These have
fillers that reduce capacitance between wires.

The transformers are often of toroidal construction. Many manufacurers will
make these as either 1:1 or stepdown types. Using a 1:1 in front of an ac-dc
converter would not be very cost effective.

Another possibility may be to use a rechargeable battery with a high
isolation relay to switch between charge and operate. You could then use an
ac-dc of lower rating to recharge the battery. This is a good compromise for
equipment of medium current draw/short patient contact time. Without knowing
the particulars of your situation I cannot give more specific advice.

Best Regards,
Scott Lacey
Test Engineer (contract)
EMC, Safety, Performance Verification

-----Original Message-----
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron
Sent: Wednesday, August 29, 2001 11:26 AM
To: EMC
Subject: Medical application-Isolation voltage



I have a medical application that requires "double insulation" from the
Mains to an "applied part" according to IEC60601.  IEC60601 states that for
a reference voltage of 250v and double insulation, the test voltage is 4000v
for 1 min.  I am assuming that the voltages are RMS values.

How does one go about meeting the 4000v test when the highest rated ac-dc
converter I can find is 3500v RMS  continuous.

Any help is appreciated.
 Thanks.




Ronald Cyprowski
Vascor Inc.
566 Alpha Drive
Pittsburgh PA 15238
412-963-7438 x139
r...@vascor.com


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