KK,
In our work with space and military products, we have had to deal
with both types of wire insulation. To answer your first question, Tefzel
is much more resistant to cold-flow than Teflon. Tefzel can also withstand
the constant irradiation in extended space applications. As I hear it,
Teflon is degraded and turns to powder, or at least crumbles in long-term or
high radiation environments. This is why some space-rated connectors with
self-leads require Tefzel. I don't know how cold-flow is quantified.
We also fabricate some of our own specialty transformers and use
Teflon insulated wire for lead-outs without incidence. Thermal stripping
Tefzel, as you probably know, is like trying to cut hot chewing gum, so
production hates the stuff. Teflon wiring is used here predominantly and
any cold-flow issue is addressed by insulating corners the wires must pass
or adding sleeving to the wire bundle in any of the chassis wiring
applications.
With regard to cold-flow and shorting to windings in your transformer, I
would have little concern. I do not know your exact application, but
consider that the insulating film on the transformer winding wire keeps it
from shorting to itself and will, in like manner, keep it from shorting to a
Teflon insulated wire, even one who's insulation has been reduced at a
pressure point. Also consider that the insulation deformation actually
relieves some of the stress. The cold-flow may thus be limited and not
progress down to the conductor. If the assembly is additionally
impregnated, there will be no relative motion between wires to produce any
sawing effect that could aggravate cold-flow.
-----Original Message-----
From: KK Chin [mailto:[log in to unmask]]
Sent: Monday, October 11, 1999 2:33 PM
To: [log in to unmask]
Subject: [TN] Teflon and Tefzel Wire
Dear Technet friends,
We've been using tefzel (a modified teflon) insulated wires in our
transformer
assemblies. Some people are concerned that the teflon's cold-flow property
would
end up in shorts between windings where there are pressure points. My
questions
are:
- Is tefzel better than the unmodified teflon in this respect?
- How is the cold-flow characteristic quantified?
- Where can I find the "cold-flow index" of the materials?
Yours sincerely
K.K. Chin
Artesyn Technologies
Fremont, CA
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