RE: Higher Mains Frequency

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>


Not necessarily.  60Hz transformers are not a drop in replacement for 400Hz.
During my days of designing avionics for aircraft, I built many a test
fixture for 400Hz operation.  Most of the avionics I worked on were
illuminated panel type stuff, so there was lots of power at 400Hz required
to light tons of incandescent lights (LEDs on newer aircraft and retrofits).
Numerous times i attempted to use standard 60Hz power transformers in these
test fixtures to provide different
voltage levels I needed etc..., but almost always, they did not work
properly.  The cores just get way too hot to the point
where they burn the enamel right off the windings.  We always had to order
special 400Hz transformers which used a different core material.  I'm not
sure how MOTs would stand up to 400Hz though.

So, 60Hz transformerse are not a drop-in replacement for 400Hz.

 > Well, you don't need inverters for one.
 > 2nd, your 60hz transformers will probley still work on it,
 > and all smps
 > would, mabey with poor power factor but a simple modification
 > could help
 > fix that.
 > 3rd, less idle current for transformers, smaller transformers
 > for the same
 > power.
 >
 >
 >
 >
 > > >The concept indeed looks interesting, but why change an
 > already perfectly
 > > >working system!!!  60Hz is more than readily available -
 > why add the
 > > >complexities of a multi-kilowatt inverter system.
 > >
 > >Because it's fun darnit! And educational too. People
 > probably said the same
 > >about the SSTC when it was first invented.
 > >
 > >Anyway, personally I have two thoughts on this.
 > >
 > >1) By driving a transformer at a higher frequency you can
 > get more voltage
 > >before it saturates. Ferinstance an MOT at 400Hz could give
 > 12kV and (more
 > >importantly) one of those little 12v:240V transformers would
 > give 1600V.
 > >Also they have chambered plastic bobbins that give good
 > primary/secondary
 > >isolation.
 > >
 > >One could imagine an 'MMT' made of about a dozen of these little
 > >transformers in series, maybe in oil, with the 12V primaries
 > all in parallel
 > >driven off a half-bridge inverter that runs off the
 > rectified 120V line. An
 > >HVDC supply would be equally easy to make by just putting a
 > small bridge
 > >rectifier and cap on each transformer and stacking them in series.
 > >
 > >2) You can get 115V 400Hz three-phase generators cheap from military
 > >surplus. They come in ridiculous powers all the way up to
 > 60kW gas turbine
 > >powered units. Imagine a 12-MOT bank running off one of those.
 > >
 > >Steve C.
 > >
 >
 >