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Any generator experts out there?
Greetings,I have a Westerbeke 4.0KW gas genny in my boat, and I'm experiencing
the following: The genny runs like a sewing machine, and when first
started, the voltage settles right at 115. When a load is presented
(A/C for example), I'll get the typical drop from the load while the
genny adjusts, and then the genny will settle back to around 115. All
is well at this point. The problem is, when the load is removed (when
the A/C cycles), the voltage rises to 150 and stays there. I notice
an increase in engine speed as well. My initial thought is that the voltage regulator might have gone
south, but I don't know if this would explain the rise in engine
speed. I guess if the regulator doesn't control the voltage, the
engine speed will rise accordingly to satisfy the higher voltage, but
I'm no electrical engineer, so it's just a guess. Any input would be greatly appreciated! I'm planning an anchor-out
this weekend, and with the rains and heat/humidity in FL, I can't be
without A/C!!! |
rc620
Jul 13
2006
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| >already. A testament to the power supplies in modern electronics no
>doubt. Most electronics these days use "wide mouth" switcher power supplies
so they can be shipped world wide so frequency and voltage problems
don't bother them too much. Motors will be the first thing to fail if
you lose regulation. |
gfretwell
Jul 15
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| I don't believe being an alternator implies that. The regulator does
that. And the regulator circuit may be designed such that it is only
capable to maintaining a reasonable voltage when the motor is turning
at approximately the correct rpm. Not the best design but certainly
possible. I agree though, being an alternator, the rpm will control
the frequency. Seems pretty likely the governor is not reducing the throttle when the
load is removed. While I'm sure there are electronic rpm governors on
generators, my limited exposure to personal generators have all had
mechanical rpm governors. They have linkage that sticks. Also any
conventional carburator has the potential for the throttle plate to
stick even if it is being operated by a servo instead of governor
linkage. I'd look for a mechanical problem before an electrical one. gfretwell@aol.com wrote: |
jamesgangnc
Jul 14
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| Of course what you're saying is correct. I was just trying to explain
why the voltage could rise in the case of the throttle not being able
to close after the load is removed. In my car example, even if it
were fully into regulation, there will be some voltage flunctuation.
But it wasn't a very good analogy. On the genset, if it's outside the regulator's capability to reduce
exitation enough, the described runaway could happen. Unlike the car,
the voltage regulator is designed to operate in an environment where
the motor will be maintaining a constant RPM regardless of load.
Since it's not, the regulator may not be able to compensate. It still
may be just a binding throttle or broken throttle return spring. It
definitely needs to be looked at before things escalate. |
Jack
Jul 14
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| Agreed. I'm surprised he hasn't damaged something plugged into it
already. A testament to the power supplies in modern electronics no
doubt. |
jamesgangnc
Jul 14
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This is an alternator so engine speed only affects frequency. The
regulator may in fact be bad but if it really increases engine speed
there is another problem. I would suggect getting it looked at by
someone with the tools to see what is really going on. |
gfretwell
Jul 13
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| You don't get the power for free, so under load the gas engine driving
that alternator/generator must increase its throttle setting to keep
up with the increased demand. When the demand goes away, the throttle
evidently isn't closing back down, and the engine speed increases
without that extra load on it. If poorly regulated, that can increase
the voltage output as well. Think of your car idling with the lights
on, the rev it up... the lights get brighter. Conversely, keeping the
same engine speed turn the headlights off, and the voltage will rise. Does the engine speed ever slow back down on its own? Could it be as
simple as a broken/missing throttle return spring? Or maybe a binding
throttle linkage. |
Jack
Jul 13
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| >Think of your car idling with the lights
>on, the rev it up... the lights get brighter. Conversely, keeping the
>same engine speed turn the headlights off, and the voltage will rise.
That is only true until the setting of the voltage regulator is met.
In the case of your car it is not a case of the voltage going too
high, only that at very low RPMs it can't meet the regulated voltage
under load.
With a 120v generator (actually alternator) the engine should maintain
a constant 3600 RPM to keep the 60 cycles constant. The throttle may
have to open or close to maintain the output power but the RPM should
stay the same.
If the RPMs did run away the voltage regulator should be decreasing
the excitation voltage to the rotor.
There are "inverter" style alternators that alter engine speed for the
load but the voltage fluxuating is still a function of the regulator.
I would be as concerned about the wrong frequency as the voltage.
Induction motors run at a multiple of the frequency, or at least they
try till they die.
He should really have this checked by a guy with a frequency counter
and a good meter before something blows up |
gfretwell
Jul 13
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| Some generators have a rpm governor that controls the output voltage.
Sounds like yours is one of those and it's sticking open too far. When
you add a load the engine throttle gets opened further to keep the rpm
constant. When the load is removed the engine throttle is not being
backed off thus the increase in speed and voltage. rc620@hotmail.com wrote: |
jamesgangnc
Jul 13
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