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Generators and switch mode power supplies

Discussion in 'Hobby Electronics' 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 bases 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?

  2. Bob Parker

    Bob Parker Guest

    I haven't experienced any power interruptions here in Sydney for
    many months so the supply's not exactly parlous where I am.
    My cheap UPS doesn't output a clean sine wave but the PC and
    monitor (switching supplies), answering machine and modem power supplies
    (50Hz transformer plugpacks) all work quite happily from it when it
    kicks in.
    I doubt that exact waveform makes much difference to most power
    supplies, especially switching supplies. Just my 2c worth...
  3. Phil Allison

    Phil Allison Guest

    "Sylvia Else = Sillier than Anyone Else "

    ** Sylvia Else = a Pommy bitch = usenet's most notorious TROLL.

    Ever seen her pic ?

    And that's an old one !!!!!!!!!!!!!!!!!!

    Know about her being a crazy nudist who tried to get a nudist political
    party going in NSW ?

    NLP = Naturist Lifestyle Party ( Inc) .

    Sylvia was the secretary of the group.

    Wot a hooooot !!

    ** Massive fallacy.

    Sylvia lives in Frenchs Forrest in Sydney.

    Dare dispute this Sylvia and I will post you EXACT address

    - bitch brain.

    ** The fuckwit pommy bitch has no idea what the term means.

    ** An " inverter " is a NOT a generator


    ** Computers all have monitors and most have sound cards and video cards.

    All of which may well be negatively affected in various ways by being
    powered by a POS fucking "modified square wave " inverter.

    Go by one and FUCKING FIND OUT !!!!!!!


    ...... Phil
  4. a t e c 7 7

    a t e c 7 7 Guest

    troll.... asyou will find out .
  5. terryc

    terryc Guest

    what exactly do you want to use it for?
    the power requirements of each item?

    I expect that most stuff doesn't really care, but you will never know
    until you try it. I've heard comments about some cheap inverters (steppy
    waves) some laptop power supplies run hot, but not chased up the details.

    The only apparatus that usually needs pure or as close to it as you can
    get is stuff that is switching with mosfets(?) which need to sense the
    zero crossing.
  6. Bob Parker

    Bob Parker Guest

    Huh? I'm not a troll. At least I don't think I am...
  7. a t e c 7 7

    a t e c 7 7 Guest

    saliva is though
  8. Sylvia Else

    Sylvia Else Guest

    NSW is in a better condition. The other states show predicted reserve
    shortfalls in the coming months.

    In some ways, though, reserve shortfalls are not such a huge concern,
    because the resulting blackouts get shared around, with no individual
    group of cumstomers subject to extened periods without power.

    Of greater concern are overloaded transformers. If they fail it can take
    quite a long time for supplies to be restored. In periods of hot weather
    such events have been known.

  9. So what's the big deal if it *does* happen?
    Not the end of the world.
    Go for a walk, go shopping, go visit a friend, read a book by torch or
    candle light, and countless other things you can do without mains

    The other week I was stuck in a lift (in Frenchs Forest of all places)
    for more than an hour during a blackout, it was actually quite fun.

    You'll survive, really, no need for a generator when you live in
    Frenchs Forest.

  10. **Doesn't matter. A standby generator will deliver a 50Hz sine wave. It is a
    mechanical device, comprising a petrol or diesel motor, linked to an
    alternator. Inverters are for use with battery storage systems (VERY
    expensive) Make certain you do the following:

    * Ensure your generator can cope with fridges and the like. Fridges and
    other motorised devices have huge switch-on demands and can cause generator
    output to fall dramatically, thus risking damage to the motor (load).
    * Do not even THINK about a large air con with anything but a very large
    generator, UNLESS you are using an 'inverter' type air con. These have a
    'soft start' and are suitable for use with most generators.
    * Get a Diesel or a 4 stroke type.
    * Buy one which has a lot more capacity than you think you'll need.
  11. terryc

    terryc Guest

    Who is your supplier?
    I'm on Integral and you expect a few hours once a month. I suspect
    they are butchering the wrong trees.
  12. terryc

    terryc Guest

    double the rating?
    And have a place out side that gets a good breeze flowing away from the
    house to run it. The USA provides a continual stream of stories of people
    who ran the generator inside and experienced why you do not do this.
  13. Mr.T

    Mr.T Guest

    Great consolation for those tens of thousands without power for their
    fridges and freezers during the recent heatwave down south.
    Sure have, and the resulting fires in some cases burnt homes or factories to
    the ground!

    Still profit is more important than minor supply and maintenance issues.

  14. Mr.T

    Mr.T Guest

    It was pretty close for some people in South Australia. Their burnt out
    homes and factories anyway!

  15. Mr.T

    Mr.T Guest

    I attended the funeral of someone who also discovered it the hard way. You'd
    think the number of people using a car exhaust to commit suicide might give
    some clue though.

  16. **That's the figure I've been told. However, I suspect it has a lot to do
    with the manufacturer. Quality manufactured products probably have short
    term overload capacity built in. Those cheap, Chinese generators from
    Bunnings probably barely meet their own specs.
    **Indeed. It's amazing how stupid some people can be. I'm clearing 30-odd cu
    Metres of soil and rock from under my house. I'm doing it by hand, or with
    electrically powered tools only. It's bloody hard yakka. A few smartarses
    have suggested I should hire a DingoT and get the job done in a few days.
    Sheesh! There's no air flow under there and almost no viable method to push
    much air through either. I'd be lucky to last 30 mins.
  17. Mr.T

    Mr.T Guest

    You could use an oxygen tank, or an externally pumped air supply if you
    thought it worth it. I'm guessing you don't.

  18. **You guessed right. Logistics beat me everytime I thought it through.
    * I'd need to remove two door frames (not such a huge deal, but
    inconvenient). There's around 2cm clearance for a DingoT at present. I'm
    told that is sufficient to guarantee damage. Then there's the (lack of)
    security thing, whilst the job is progressing.
    * I'd need to organise bins to cart away the 50cu Metres (as you probably
    know, the stuff 'fluffs' up, when you dig it) of stuff. I can only manage 2
    cu Metre bins at any one time.
    * Based on the above, I'd need a DingoT for a great deal longer than the
    optimum period of 2 days. I'd reckon on at least a month. Too expensive.
    * I'm not in a desperate hurry. If I was, I'd pay some guys to do it.

    I'll keep doing it by hand. It's good exercise.
  19. terryc

    terryc Guest

    Been there done that when we were younger.
    If it requires drainage, make sure that the drainage hose is below the
    concrete slab.
    You could probably hire a mine ventilator tube as well. The real problem
    is when they ggraze the foundations.
  20. kreed

    kreed Guest

    Regarding "inverter" generators:

    Honda (and possibly others) now offer generators with an inbuilt
    sinewave "inverter" in
    order to provide high quality power (presumably crystal locked to
    50hz) for sensitive
    equipment regardless of generator motor speed fluctuations etc.
    This would also allow lower engine speeds at low load to save fuel,
    without affecting the output frequency

    Another advertised advantage of this system is the ability to link 2
    of these
    units together in parallel via a special cable (available from Honda)
    in order to increase the total output capacity.
    This would probably have extra wire(s) to ensure the inverters outputs
    are synchronised, their output voltages as close as possible to each
    other to keep the load balanced between the 2 inverters/generators ?

    this provides 30a @ 120v (equivalent to a 15A 240v socket.) (note -
    this is for US use only, there would be an Australian version.)

    The other advantage that this dual system MIGHT have is the ability
    to keep critical equipment in the home (such as life support) running
    in the home if one of the two generators fails, as long as the total
    load is sufficient for one unit.
    (NOTE: I don't want to go round giving advice on this, or saying its
    100% foolproof, or legal, or safe in case Im wrong and someone is
    hurt or dies, please seek expert advice from the supplier or
    manufacturer or other expert before using or relying on this or any
    other method of powering life support)

    For most people, I think this sort of unit would be an good choice for
    occasional temporary emergency home use of lighting, computers, phone
    charges etc etc and you can be sure it will run ANY sensitive
    equipment just as well as off the mains. Gas rings would be more
    efficient for cooking, boiling water etc.

    Trevor's comments on selecting a generator should be noted also.
    regarding large loads, fridges air cons etc,

    2 problems I can recall with use of non-mains power are :

    Note there was a letter from a reader in silicon chip recently
    regarding use of a generator powering a battery charger on a boat, the
    battery charger wouldn't start at all with one particular generator
    (probably because of low quality or noisy power) and worked perfectly
    with another.

    Another problem I have had personally is with my Dewalt cordless drill
    I bought in the 1990s when they first came out.
    It charged perfectly on the mains, but wouldnt charge on a modified
    square wave inverter (note: true sine wave inverters/generators
    wouldn't give this problem) we used in the work van. IT turned out to
    be a "series capacitor" type power supply (transformerless).
    Fortunately it charged pretty fast compared to the older cordless
    drills, and armed with a spare battery we just charged it off the
    mains at places where we were doing jobs.

    These are examples of where a TRUE SINEWAVE inverter generator would
    be of benefit.

    I dont think a PC would need this and would work happily off a square
    wave or modified square wave inverter (this is what most UPS provide.
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