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Thoughts on running 50/60 Hz SMPS on 400 Hz

Discussion in 'Electronic Design' started by Dave, Jun 13, 2008.

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  1. Dave

    Dave Guest

    I need to use some equipment in an aircraft which only has a 400 Hz
    supply. My believe is that a switch mode power supply should not really
    care too much if the supply frequency is higher. Anyone any experience
    of using normal 50/60 Hz SMPS's on 400 Hz?
  2. Joerg

    Joerg Guest

    That, and the y-caps in there might throw you a curve. Bottomline the
    manufacturer of the power supply would have to be asked.

    Most likely they would not endorse use in an aircraft anyhow. Possibly
    it would also require an STC blessed by the FAA -> $$$.
  3. Phil Allison

    Phil Allison Guest


    ** So your idea of a " normal " SMPS is what ??

    One that has no PFC circuit ?

    That could become a big problem if not designed for a frequency 8 times
    higher than usual.

    Also, 400 Hz and its harmonics are far more likely to become injected into
    places you don't want them by induction and capacitive coupling than 50 Hz.

    Maybe you can rig up a temporary 400Hz (at 230 volt ?) supply - using an
    audio power amp and a mains transformer (operating in reverse) to see what
    happens with your particular gear.

    ....... Phil
  4. Phil Allison

    Phil Allison Guest

    "Paul Mathews"

    ** DC mains supply was abandoned about 100 years ago - for darn good

    Even then it was only 240V DC not 350 V DC !!!

    IMO - the fire safety hazards and risk of accidental misconnection of
    transformer loads are too great to even contemplate this option.

    ...... Phil
  5. Dave

    Dave Guest

    You are correct. Also, the aircraft will not be flying.
  6. Phil Allison

    Phil Allison Guest

    "Paul Mathews"

    ** That is a total red-herring.

    Even building one 230AC to 350 volt DC supply adaptor is very dangerous -
    since the only practical way to do it is to use domestic 230 volts AC
    connectors at the output.

    The fire risk is way too high.

    ...... Phil
  7. Tim Williams

    Tim Williams Guest

    -- "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.

  8. Phil Allison

    Phil Allison Guest

    "Tim Williams"
    "David Starr"

    ** But not for a given transformer and fixed primary voltage.

    Raising the input frequency by a factor of 8 reduces the core magnetisation
    by a similar ratio - so core losses remain much the same or even reduce.

    ....... Phil
  9. 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

    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 ()
  10. Tim Williams

    Tim Williams Guest

    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?

  11. Phil Allison

    Phil Allison Guest

    "Tim Williams"

    ** Fuckwit TOP POSTER !!!!!

    ** Wanna think that last bit of drivel through again ??

    ..... Phil
  12. Making laminations thinner is done to reduce eddy current loss. With
    that loss (and source of heat) being about the same at 50, 60 and 400 Hz,
    making the laminations thinner makes things better at all of these

    I suspect the laminations are thinner either as part of the transformer
    being a better one, or to counter increased core loss by using lower cost
    core material or skimping turns/volt. This is to make a cheap transformer
    less bad, or to make a good one better. Less heat from the transformer
    may be something sorely needed in something as compact as many modern

    Someone I have worked with tells me that a pretty good quality core
    material with fairly reasonable (not bargain basement) cost is "29M6".
    That comes in laminations thinner than those in the usual fare from low
    bid contract manufacturers.

    - Don Klipstein ()
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