when generator is overloaded

 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

 

   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)


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


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


   Usually not.


   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

 


providing

in such

shut

"brown out"

back-to-back

down,

outage

repeated


  to add to the good reply from Vaughn ..
Prudent load management is the key - if you want to
run your home from a  3 - 5  kw generator.
 I have a Honda 5000 that feeds my home quite nicely ..
  -  except  -
 I shut off everything else - when I need to pump water.
 No big electric heater elements and no air cond.
 No  "idle down" fuel savings - the phantom loads will easily beat-out
the idle-down  limit.  ( 40-50 watts )
 Fuel consumption - I can just barely make it through the night on a
tankful .. 7 hours.. at nothing near full load ..  3 - 4 gallons.
  That said  -  I have sat through 30 hour
southern Canadian February grid power failures
while the gas furnace, gas water heater, fridge, freezer, computer,
TV, lights, etc   are quite happy  ..  
  If your needs are more critical - or for long duration -
do not rely on a little 3600 rpm consumer generator.
  They are also quite noisy.
  I can't say that I've had my generator poop-out or overload
under critical load ..  I can't say how the loads would react.
  jt

 

nominally providing

typically in such

just shut

"brown out"

back-to-back

shut down,

power outage

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.