Dear Mal, LF
Group,
No – it is possible
to design these transformers with a small air gap, but there does not appear
to be a great advantage to doing so because the required number of turns
increases, increasing the “copper” losses and offsetting any reduction in core
loss. There is always a quite large gap in the original LOPT – often this is
produced by inserting plastic film spacers between the core halves. These, and
any glue, should be removed so that the core halves fit together perfectly.
Sometimes the gap is produced by machining the core legs to unequal lengths,
in which case you can’t really use the core in this
application.
Cheers, Jim
Moritz
73 de
M0BMU
Tnx Jim for the info.
My LOPT cores have equal leg length, and in the past I have removed the
plastic spacers when present and they work well. This appears to be what u
have done ie no gap.
Thanks to all the
others as well for their info.
I am working on the
project at present. I notice up to a few hundred watts there never seems to be
a problem with heat, explosions etc but when aiming for
an o/put of 1 kw things are more critical, 2 cores needed, more
robust wire on the transformer. My present project uses 2 x 26A/500V Fets
on each leg ie total 4. I am hoping to get up to about
100v and see what happens. So far I have managed 800w out at 40v/22amps
but above this things get tricky, pa getting hot and the winding on
the o/p transformer getting warm. The design is similar to YXM/MRF with a
few refinements.
I happen to have
these fets so I am trying them out, lets hope they
survive !!!!!!!!
All suggestions
welcome. In the past I have used low voltage high current up to 60Amps and all
has been well but going to a higher voltage and lower current the PA
performs differently even though this would appear a better approach,
using the above Fets.
I should really use
my Decca and save myself a lot of trouble with home built gear, but then there
is not the same satisfaction when working the DX !!!!!!
73 De
Mal/G3KEV
-----Original
Message-----
From:
[email protected] [mailto:[email protected]]
On Behalf Of hamilton
mal
Sent: 31 March 2005
13:36
To:
[email protected]
Subject: LF: TX Cores
Jim ur mod to the G0MRF using a TV
line output transformer. Did u leave a gap between the cores or not
?
