when generator is overloaded

Discussion in 'Home Power and Microgeneration' started by Mark L., Jul 10, 2008.

  1. Mark L.

    Mark L. Guest

    am attempting to size a generator and have a couple stupid questions.

    assume a generator wired via manual or automatic transfer switch, nominally providing
    about 3-5 kilowatts of power, about 22-24 amps

    apart from an overload shutting down a generator, what else occurs, typically in such
    a situation? does it cause home appliances to "burn" or do these typically just shut
    off similar to what would happen when a power utility has what is called a "brown out"
    or low voltage situation? sometimes our local power utility has multiple back-to-back
    low voltage events, causing appliances to stop-start-stop

    how does a "brown out" differ from a generator overload caused low voltage shut down,
    aside from the fact that the generator of course will turn off and the power outage
    becomes a "black out".

    does a generator experience permanent harm from an overload, assume it's not repeated
     
    Mark L., Jul 10, 2008
    #1
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  2. Mark L.

    Vaughn Simon Guest

    "Mark L." <> wrote in message
    news:g53hif$bsr$...
    > am attempting to size a generator and have a couple stupid questions.


    As you have already figured out, size matters. That said, especially in
    these days of expensive fuel, bigger is not necessarily better. You must figure
    out what your load is and size your generator accordingly. (Or figure out what
    your generator can handle and size your load accordingly)

    > apart from an overload shutting down a generator...


    Many/most generators do not have a true overload shutdown. That can be a
    real problem if you don't manage your load.

    >what else occurs, typically in such a situation?


    Worst case; the "magic smoke" comes out of your generator.

    >does it cause home appliances to "burn"...?


    Usually not.

    > does a generator experience permanent harm from an overload, assume it's not
    > repeated


    Yes, it can.

    You need to know your load. You already seem to know the relationship between
    current and power. One way to manage your load is to build a simple adapter so
    that you can use a cheap "clamp on" AC ammeter to measure current. Another way
    is to use a manual transfer panel with built- in wattmeters. A common way is to
    keep track of what you have connected to the generator and estimate your total
    load using simple addition.

    My whole-house generator is only 4 KW. That means that I must shut down my
    central air, my oven & range (hot water is gas). That done, our typical load is
    under 2 KW. Why so small? Because we can have weeks-long power failure in our
    area and even that little generator could burn hundreds of $ worth of fuel in a
    single week. Imagine what a big one could cost to run?

    Vaughn
     
    Vaughn Simon, Jul 10, 2008
    #2
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  3. Mark L.

    Ulysses Guest

    "Mark L." <> wrote in message
    news:g53hif$bsr$...
    > am attempting to size a generator and have a couple stupid questions.
    >
    > assume a generator wired via manual or automatic transfer switch,

    nominally providing
    > about 3-5 kilowatts of power, about 22-24 amps
    >
    > apart from an overload shutting down a generator, what else occurs,

    typically in such
    > a situation? does it cause home appliances to "burn" or do these typically

    just shut
    > off similar to what would happen when a power utility has what is called a

    "brown out"
    > or low voltage situation? sometimes our local power utility has multiple

    back-to-back
    > low voltage events, causing appliances to stop-start-stop
    >
    > how does a "brown out" differ from a generator overload caused low voltage

    shut down,
    > aside from the fact that the generator of course will turn off and the

    power outage
    > becomes a "black out".
    >
    > does a generator experience permanent harm from an overload, assume it's

    not repeated
    >


    Inverter generators will simply shut down the output if overloaded. I doubt
    they would cause any spikes or low voltage problems.

    My personal experience with overloaded generators is that (usually) the
    circuit breaker trips. Or the coils burn out or melt. None of my
    non-inverter generators will "shut down" due to an overload. At least not
    to my knowledge. Some generators will keep struggling along without
    tripping the breakers but you should be able to hear it struggling and the
    lights will be dim etc.
     
    Ulysses, Jul 12, 2008
    #3
  4. "Ulysses" </> wrote in message
    news:yR6ek.56$...
    >
    > "Mark L." <> wrote in message
    > news:g53hif$bsr$...
    >> am attempting to size a generator and have a couple stupid questions.
    >>
    >> assume a generator wired via manual or automatic transfer switch,

    > nominally providing
    >> about 3-5 kilowatts of power, about 22-24 amps
    >>
    >> apart from an overload shutting down a generator, what else occurs,

    > typically in such
    >> a situation? does it cause home appliances to "burn" or do these
    >> typically

    > just shut
    >> off similar to what would happen when a power utility has what is called
    >> a

    > "brown out"
    >> or low voltage situation? sometimes our local power utility has multiple

    > back-to-back
    >> low voltage events, causing appliances to stop-start-stop
    >>
    >> how does a "brown out" differ from a generator overload caused low
    >> voltage

    > shut down,
    >> aside from the fact that the generator of course will turn off and the

    > power outage
    >> becomes a "black out".
    >>
    >> does a generator experience permanent harm from an overload, assume it's

    > not repeated
    >>

    >
    > Inverter generators will simply shut down the output if overloaded. I
    > doubt
    > they would cause any spikes or low voltage problems.
    >
    > My personal experience with overloaded generators is that (usually) the
    > circuit breaker trips. Or the coils burn out or melt. None of my
    > non-inverter generators will "shut down" due to an overload. At least not
    > to my knowledge. Some generators will keep struggling along without
    > tripping the breakers but you should be able to hear it struggling and the
    > lights will be dim etc.



    Depending on the design and size of both the motor driving it and the
    alternator different things can happen



    If you overload the alternator to the extent that it exceeds the capability
    of the motor to supply enough power to drive it and it is a straight forward
    motor alternator (not an inverter model), the alternator will slow down
    causing the frequency to drift, any electric motor on the electrical system
    will also slow down, or could stall. Electric motors prefer a fixed
    frequency or cycles (Hz) The more you overload it the slower the alternator
    will turn and the slower the electric motors will run. If the overlaod is
    severe enough it could cause the motor driving the alternator to stall.



    Most alternators are capable of a limited overload for starting purposes of
    electrical motors, but a sustained overload will cause the breaker to trip
    or and the burning out of the alternator.



    Running an alternator above its rating for any length of time can cause the
    windings to overheat and be damaged, and although this might not at the time
    be sufficient to cause the alternator to burn out then, it could cause
    problems later on in shortening the life of the altermnator.
     
    RamRod Sword of Baal, Jul 12, 2008
    #4
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