Ron B.
Guest
Thu Mar 23, 2006 5:02 am
In a DC to DC converter operating at 400 cycles at less than 450 volts
what would give you the least amount of drain from a 12 volt battery?
A pot core or E core transformer.
Thanks,
Ron
Guest
Thu Mar 23, 2006 3:40 pm
On Wed, 22 Mar 2006 22:02:43 -0600, "Ron B." <rmboz_at_everestkc.net>
wrote:
Quote:
In a DC to DC converter operating at 400 cycles at less than 450 volts
what would give you the least amount of drain from a 12 volt battery?
A pot core or E core transformer.
Thanks,
Ron
Place I worked at built 400 HZ power supplies for the military. We
wound our transformers with EI laminations. We used a special
lamination suited to the purpose - high silicon content, grain
oriented, nickel-steel alloy, and very thin (something like .007") I
think the grade was something like M4 (but could be wrong there)
There were no ferrites that could come close at 400 HZ - at least that
was the case in the 70's.
Another consideration - our military products were for aviation use.
The on board power plants supplied sine-wave power to us. If your
converter is square wave that may change things a little.
EI laminations can go well above 400 HZ and remain efficient, but the
iron gets more expensive (and smaller for the same power).
Ribbon wound toroids are another choice for mid frequency high power
applications. Very efficient, low magnetic field leakage, and
relatively hard to wind by hand.
BUT if I were building a DC to DC converter - as you state. I'd work
well above 400 HZ and use a cup core or ferrite toroid.
Why would you build at 400 HZ?
In many DC-DC converters your oscillator relies on driving the core to
saturation - the typical two transistor push pull oscillator.
Saturating iron can become inefficient. To get around that loss they
frequently use a small transformer for the feedback and just allow it
to saturate not the main power transformer. Another trick is to use a
gapped core with a small section with no gap - the small section
saturates and provides the current reversal to oscillate.
http://ludens.cl/Electron/Electron.html has some info on hobby power
supply transformer design. There's an example of the gap/no-gap core
in the fluorescent lamp driver section.
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