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power conditioning

Discussion in 'Electronic Repair' started by [email protected], May 28, 2006.

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  1. Guest

    This is probably an old question, but here it goes again.

    I have recently bought a generator for emergency use. I want to
    occasionally use it to power the tv and/or computer equipment. I have
    read numerous posts that state some generators operate electronic
    equipment ok and many that say it fried the electronics. So here's the
    question: What type of power conditioning is best for interfacing the
    generator power to electronics? UPS? Inverter? Other?

  2. Mike Berger

    Mike Berger Guest

    The best way to run your electronics on backup power is with DC,
    using the generator to charge the batteries. High-reliability
    Telco and network equipment is powered by 48 volt inverters.

    Most smaller UPS's don't work well on power from small generators.
    The voltage and frequency will both be too unstable. They'll keep
    switching back and forth between line voltage and inverter.

    So if you're running anything besides lights and motors from the
    generator, you're taking a chance with out-of-spec noisy power.
  3. Guest

    OK, inverters come with outputs in true sine wave and modified sine
    wave, with the modified wave units being more common and cheaper. Will
    tv's & computers work ok with modified sine wave inverters?

  4. Guest

    Actually, the cheapest and the most common inverters have
  5. Mike Berger

    Mike Berger Guest

    For the most part, yes.
  6. I wonder about the initial assumption that a small generator is unsafe
    for TV/PC. Isn't the generator's output pretty close to a perfect sine
    wave - better than what comes out of a UPS? The frequency may go up and
    down a bit - I don't think this is a big problem unless you are using a
    turntable. Voltage will waiver but if you don't overload the generator
    this might not be too bad.

    If you wish to use a UPS w. the generator, be sure to buy one that has a
    sensitivity switch to ignore generator variations.
  7. Mike Berger

    Mike Berger Guest

    They're unsafe in that the voltage and frequency can fluctuate wildly
    especially as the load changes. I'm sure some consumer electronics
    devices will handle it fine, but most of it isn't designed with wide
    operating margins these days.
  8. Mike Berger

    Mike Berger Guest

    In your experience which ones work ok with generators? None of my
    APC SMART-UPS or Matrix UPS controllers do, even at lowest sensitivity.
    The very high end Lieberts work, but they're extremely expensive.

  9. No. Take a look at the output with a scope and you'll see.
  10. Bud--

    Bud-- Guest

    Any idea why it isn't a sine wave?


  11. It would take way too much typing. Find a college EE book on power
    generation and distribution, then prepare for some heavy reading.

    In layman's terms, its the transformers and motors that help clean up
    the power on the grid and you don't have all that to help filter the
    output on a single small generator.
  12. Mike Berger

    Mike Berger Guest

    Not to mention the serious phase shift.
  13. I stand corrected about suitability of small generator for TV/PC.
    I found the following APC FAQ's very helpful. Also addresses waveform
    of small generators (with non-linear loads).
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