Re: Thoughts on running 50/60 Hz SMPS on 400 Hz

Hmm, I'll believe that, but then, if that's the case, why ARE the
laminations thinner in my scope's transformer? Why use thin laminations at
any frequency if it factors out?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


"Don Klipstein" <don@xxxxxxxxxxxxxx> wrote in message
news:slrng5d3us.k8k.don@xxxxxxxxxxxxxxxxx
In article <iNh5k.6127$613.1414@xxxxxxxxxxxx>, Tim Williams wrote:
"David Starr" <dstarrboston@xxxxxxxxxxxxxx> wrote in message
news:485549bf$0$4235$4c368faf@xxxxxxxxxxxxxxxxx
We used to run 60 Hz test equipment on 400 Hz power on the flight line.
Good stuff, Tektronix say , ran no problem. Aircraft selected 400 Hz to
reduce the amount of iron needed in inductors, transformers, generators,
and so forth. 60 Hz supplies (transformer, rectifier, filter caps,
linear
requlators) have plenty of iron and capacitor size to work on 400 Hz.

-- "Too much", actually. The transformer in my Tek 475 has quite thin
laminations. It's rated for 50-400Hz, of course. Eddy current losses go
up
with frequency.

Eddy current losses are proportional to square of frequency and square
of magnetic flux. (At frequencies low enough for this to not get
complicated much by skin effect, stray inductances, whatever)

However, volts per turn is proportionate with magnetic flux and
frequency. That means eddy current loss is proportional to square of
volts per turn, unaffected by frequency.

Hysteresis losses are actually improved by using a higher frequency.
Those are *roughly* proportionate with square of magnetic flux but only
linear with frequency - so with constant volts per turn, this loss is
roughly inverse proportional to frequency.

(Hysteresis losses have messy nonlinearities, and the above is an
oversimplification.)

The usual problem with operating 50/60 Hz iron core transformers at 400
Hz is that leakage inductance in the transformer sometimes causes output
voltage to be less (with load) at 400 Hz.

- Don Klipstein (don@xxxxxxxxx)


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