Re: Solid State coils.
Subject: Re: Solid State coils.
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Date: Tue, 23 Apr 1996 10:01:18 +1200
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This is a slight addition to my previous post on this topic.
I should have included a couple of notes on the design of ferrite
transformers. The typically low inductance of the windings compared
with the overall leakage inductance mandates certain construction
teahniques for best results. Firstly, both halves of the primary
should be bifilar wound to couple as closely as possible. Secondly,
the secondary is often sandwiched in between layers of primary, a
typical arangement being to wind half the primary turns (for each
primary half), then insulate, then wind the secondary, more
insulation, then wind the rest of the primary windings on top. In the
best designs, even the secondary can be sectionalized and and
interleaved with the primary. The extra insulation required to do
this plus the inter-layer creepage distance can severely restrict the
number of windings one can actually get on a given core. For example,
in SMPS transformers complying with international hipot specs, the
windings can occupy less than half the available winding window.
Whole books have been written on the subject. For Alan's application,
I think the primary should at least be bifilar wound if nothing else.