Designing a Transformer - RF Cafe Forums
Post subject: Designing a transformer Posted: Thu Mar
13, 2008 8:38 pm
Joined: Thu Mar 13, 2008
I wish to build an oscillator
of the multivibrator type, for induction
The transformer will be 1:1 with center-tap
on the primary.
Frequency between 1khz to 50khz. Needs to be
small as possible
to fit on the PC board. Now here's the rub;
needs to handle
115V-230V @ 1-10Amps, but should run off as
little as 12V.
Torroids are fine, have the ARRL Handbook 2008 and many
L calculators but am still way over my head. No idea
what core material,
size, wire size, number of turns, etc. Don't
want to inductively heat
the transformer, just the workpiece!
Suggestions welcome, and
Post subject: multivibratorPosted: Fri Mar 14,
2008 12:41 pm
Joined: Wed Feb 22, 2006
You sure have some stringent requirements.
Start with the simple ones:
Assuming your output is
230V at 10 Amps is 2300 watts, so you'll need
a big core with thick wire.
At 12V input, this is about
192 Amps - so you'll need transistors rated for at least this much
current. Likewise, at 230 V input, your transistor should be rated
for at least 500V.
200 A and 500 V transistors are rare
and expensive, and need special heat sinking and drive. You're into
specialist territory, not hobbyist or experimenter territory, if
I've interpreted your requirements correctly.
Post subject: Posted:
Mon Mar 17, 2008 6:36 am
Feb 17, 2006 12:07 pm
Location: London UK
Paddy once said: If I was goin thar I wouldn't start from here.
I agree with Fred: 12V is the wrong starting point for a system
consuming more than 1kW, and using transistors is also probably
the wrong approach.
I would be thinking in terms of 56 volts
at least, and using Triacs, not transistors. The triacs would be
driven from a reliable DIL TTL or CMOS multivibrator 4047 or similar.
Also you state the transformer is 1:1 ratio, but
with a primary of 12V and a secondary of 115V or 230V, the ratio
would be more like 10:1 or 20:1.
Are we missing something here?