[armyradios] Re: [Milsurplus] Cheap 400hz power

[J. Forster]

papakb1 wrote:

> Gentlemen,
>
>     Keep in mind that merely by changing the frequency determining components of a UPS
> to generate 400hz power you aren't solving all of your problems.  The reason that 400hz
> was used in aircraft was because the transformers for 400hz circuitry are smaller and
> lighter because there is less steel required in their cores.  Simply changing the
> frequency of a 60hz UPS doesn't overcome the fact that their transformers (or torroids)
> are also designed for 60hz operation. You'll probably end up frying the transformers.
>
> Kurt

Not necessarily so. The amount of core material used in a transformer is set by
saturation
peak) the flux level. At lower frequencies, the peak flux level is higher, all
other
things remaining constant, because the flux is proportional to an integral which
includes
time. For this reason, a 400 Hz transformer fries on 60 Hz or a 60 Hz on 50 Hz.

OTOH, the high frequency limit is set by core loss (loss in the core material).
This loss
is dependent on the lamination thickness and the material. Higher frequency
transformers
have thinner laminations. Tektronix used to make scope transformers that worked
from 50 to
at least 400 Hz. If the core is ferrite, they should work to quite a high
frequency. I
think the idea is worth a try. Worst case, the transformer will get very much
hotter than
60 Hz, and this is observable.

BTW, there may be more to change than just a timing component. There could well
be
filters, both at low level, and high power output filters. If there's a second
or third
harmonic filter, it's gonna try and take out all your 400 Hz.

Good luck. Keep us poster,
-John