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Generators and switch mode power supplies.

Discussion in 'Electronic Design' started by Sylvia Else, Feb 4, 2009.

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  1. Sylvia Else

    Sylvia Else Guest

    Given the parlous state of Australia's power systems, I've been
    considering buying a standby generator. One marketing point of some of
    the inverter based models is their suitability for 'sensitive
    electronics' with computers given as an example. This appears to be
    based on the fact that they'll provide a consistent sinewave output.

    But given that computers invariably use switch-mode power supplies, are
    they actually going to care what waveform they see - from square wave
    thru 'modified sinewave' thru pure sinewave?

    Sylvia.
     
  2. TheM

    TheM Guest

    Well, usually switcher has a full-wave rectifier and a smoothing cap
    at the input. This means it probably works fine even with DC voltage.
    The PC and similar stuff should be happy.

    Stuff that runs through transformers may not like square wave.

    You could run it through a good UPS (the kind that rectifies and re-generates
    AC) to get good regulation and waveform.

    M
     
  3. ZACK`

    ZACK` Guest

    if you have store that sells the scorpian range
    theres a new type of genset, thay are the
    permanant magnet pure sinewave range, thay will run anything.

    i have one of these its a 6.8kva model PM6500LX
    thay have no electronics in them to go wrong
    no brushes no caps no inverters.
     
  4. Guest

    I fried a notebook power supply on a modified since wave inverter. I
    won't run any electronics on those beasts again. However, I don't know
    the mechanism of why the modified sine inverter fried the power
    supply. Given how a switching supply works, I didn't consider feeding
    a switcher with a cheap inverter to be a problem, but reality was
    different. Well, it was only a $100 lesson. It the notebook got fried,
    I think I would have been a little more POd. If I had to run
    electronics on a generator, it would be with one of those inverter
    generators.

    The other advantage to the inverter generators is they worked on
    making them quiet.

    Incidentally, generators are pretty easy to get used. People buy them
    for a particular lifestyle (say camping in the outback), then
    circumstances change (a newborn in the family keeps them at home,
    etc.).
     
  5. Phil Allison

    Phil Allison Guest

    "Sylvia Else"
    ** Pure marketing hype.


    ** All generators provide a reasonable sine wave.

    But some do not have a steady or accurate frequency.


    ** No *generator* ever puts out a square wave or modified square wave.

    You are BARKING up the wrong tree BITCH.




    ...... Phil
     
  6. Guest

    You can get -48V supplies for PCs, rather than run of AC. I don't
    think I ever saw a PC supply that did both AC and DC, but that would
    be a nice product.

    http://www.trcelectronics.com/48-volt-power-supply.shtml
    is the first google hit.
     
  7. Sylvia Else

    Sylvia Else Guest

    Really? Well, I suppose it depends on your definition of "reasonable".
    How about this one?

    http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_cycloconverter

    I dare say few devices would be upset by that, but it's clearly nothing
    like a pure sinewave.
    Did I say that it did? Don't think so.

    Sylvia.
     
  8. Phil Allison

    Phil Allison Guest

  9. Sylvia Else

    Sylvia Else Guest

    I was thinking specifically of the inverter based generators, which have
    engine speeds that vary with load, but which maintain a constant
    frequency and voltage. I presume they rectify the AC output from the
    generator proper (or use a DC generator) then synthesise some
    approximation to a sinewave in the same way that a battery input
    inverter would.
    I found this page discussing a Yamaha inverter based generator. It
    includes oscilloscope traces of the output, which is clearly a pretty
    good sinewave. I haven't been able to find any indication of the
    technology used for this (unless it's the obvious method involving
    filtering).

    http://2manytoyz.com/yamaha2400.html

    Sylvia.
     
  10. Sylvia Else

    Sylvia Else Guest

    What is a "generator" Phil? A device that generates? The Honda device
    chugs away happily (I assume) generating power. The cycloconverter is
    part of the mechanism.

    Sylvia.
     
  11. Nico Coesel

    Nico Coesel Guest

    Not really. A computer doesn't care much as long as the voltage is
    within range. One thing to consider is that computers are a bad load
    to a generator. As a rule of thumb you need a generator with at least
    twice the VA rating as the total VA rating of all computers. Otherwise
    the generator cannot keeps its rpm constant (starts speeding up and
    slowing down).
     
  12. Phil Allison

    Phil Allison Guest

    "Sillier than Anyone Else"

    ** In the CONTEXT where I used the word - it referred to a small, petrol
    motor driven, single phase alternator.

    You pig ignorant TROLL.



    ...... Phil
     
  13. Sylvia Else

    Sylvia Else Guest

    That'd be right. Change the context without notice.

    Sylvia.
     
  14. Phil Allison

    Phil Allison Guest

    "Sillier than Anyone Else"

    ** ROTFL !!

    Wot a massive fucking NUT CASE & DAMN LIAR you are !!




    ....... Phil
     
  15. Sylvia Else

    Sylvia Else Guest

    I assume that's related to the harmonic load represented by switch mode
    power supplies.

    Circuits for significantly improving the harmonic performance have been
    around for a decade, but I suppose little will happen until legislation
    requires their use.

    Sylvia.
     
  16. Nobody

    Nobody Guest

    I assume that was referring to the variation in power consumption between
    busy and idle.
    EU legislation has required their use for some time (2001, AFAICT).
    Specifically, most power supplies above 75W must comply with
    IEC/EN61000-3-2, with computer PSUs conforming to class D.

    In practice, this means that a typical ATX PSU starts with a boost
    converter whose current waveform is roughly sinusoidal, and in phase with
    the line voltage.

    Although this isn't required in the US, I would assume that most PSUs will
    have been designed to meet EU standards anyhow (cf RoHS).

    FWIW, an application note on PFC:

    http://www.onsemi.com/pub_link/Collateral/HBD853-D.PDF
     
  17. JosephKK

    JosephKK Guest

    May not have happened yet down there, but has been around for about 2
    decades in the US now.
     
  18. JosephKK

    JosephKK Guest

    Power factor correction and harmonic suppression are two different
    things. It is just convenient that typical PFC circuits also reduce
    harmonics.
     
  19. Nobody

    Nobody Guest

    True enough.

    However, although the aforementioned "PFC" app note is titled "Power
    Factor Correction (PFC) Handbook", it immediately starts by discussing
    harmonics, EMI, and EN 61000-3-2 (which regulates harmonics rather than
    power factor per se).

    The EPSMA guide says:

    The corresponding electronic circuitry is often called Power Factor
    Correction (PFC) circuitry, although power factor correction is not the
    correct wording but has become synonymous for harmonic line current
    reduction

    http://www.epsma.org/pdf/PFC Guide_April 2005.pdf

    And then implicitly re-iterates the informal use by using the filename
    "PFC Guide_April 2005.pdf", although the title is "Harmonic Current
    Emissions - Guidelines to the standard EN 61000-3-2".
     
  20. Sylvia Else

    Sylvia Else Guest

    Could be, I suppose, though whether the generator can keep its RPM
    constant (or rather, within acceptable bounds), would depend on how fast
    it can change its throttle setting.

    Sylvia.
     
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