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Posted by RamRod Sword of Baal on July 12, 2008, 3:24 pm
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>
>> 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.
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