My engine panel overspeed alarm is driven by the freq output from the
alternator from the AC taps. The overspeed alarm goes off when the
alternator speed is 5000rpm, equiv to engine speed 2300rpm. With a new
alternator, I've reduced the pulley size considerably and the alt speed
is 5000 rpm at 1400 engine rpm - and the alarm now goes off.
The engine panel has a pot to adjust the overspped freq but looking at
the service bulletin the freq will be outside its adjsutment range
I've got 2 options - the easy one - disconnect the wire - is an
overspeed really necessary or useful??
Try and get a device to divide the frequency.

Grateful for any ideas.

CS inscribed in red ink for all to know:
My engine panel overspeed alarm is driven by the freq output from the
alternator from the AC taps. The overspeed alarm goes off when the
alternator speed is 5000rpm, equiv to engine speed 2300rpm. With a new
alternator, I've reduced the pulley size considerably and the alt speed
is 5000 rpm at 1400 engine rpm - and the alarm now goes off.
The engine panel has a pot to adjust the overspped freq but looking at
the service bulletin the freq will be outside its adjsutment range
I've got 2 options - the easy one - disconnect the wire - is an
overspeed really necessary or useful??
Try and get a device to divide the frequency.

Grateful for any ideas.


change the alternator pulley back to the one from the old alternator?

bob

Colin,

It would be neat if you gave us any idea what this is about:
What engine,
What alernator
anything else that might interesting.

Are you so far from the engine that you could not hear it?

Matt Colie

CS wrote:
My engine panel overspeed alarm is driven by the freq output from the
alternator from the AC taps. The overspeed alarm goes off when the
alternator speed is 5000rpm, equiv to engine speed 2300rpm. With a new
alternator, I've reduced the pulley size considerably and the alt speed
is 5000 rpm at 1400 engine rpm - and the alarm now goes off.
The engine panel has a pot to adjust the overspped freq but looking at
the service bulletin the freq will be outside its adjsutment range
I've got 2 options - the easy one - disconnect the wire - is an
overspeed really necessary or useful??
Try and get a device to divide the frequency.

Grateful for any ideas.

Engine is a Daewoo L136 and the original alternator, 50A 5000 rpm max
continuous, was replaced by a Leece Neville unit, 110A 8000 rpm max
cont . To get more amps from the alternator, I reduced the pulley so
8000 alt rpm is now achieved at just over 2300 engine rpm - engien
normal max is 2200 rpm. The engine is beneath my feet in a luxemotor
barge - so I think the oversped is somewhat superfluous.

Colin,

Don't sweat the overspeed.

Unfortunately, this engine is too new for my catalogues, but I and quite
sure that it is using a Hitachi copy of a Bosch TE injection pump. This
pump includes a controlling governor that not only controls the engine
to produce the ordered crankshaft speed but also limits the speed to a
safe maximum. The only way to exceed that speed is by introducing
additional fuel (often that is injested lube oil) and it that occurs
there is often little the operator can do without getting too close to
the engine.

I was glad to see that you are running double belts because that is just
about and maybe a little bit over the capability of a single belt.

Matt Colie
Lifelong Waterman, Licensed Mariner (Diesel Chief...)



CS wrote:
Engine is a Daewoo L136 and the original alternator, 50A 5000 rpm max
continuous, was replaced by a Leece Neville unit, 110A 8000 rpm max
cont . To get more amps from the alternator, I reduced the pulley so
8000 alt rpm is now achieved at just over 2300 engine rpm - engien
normal max is 2200 rpm. The engine is beneath my feet in a luxemotor
barge - so I think the oversped is somewhat superfluous.

"CS" wrote in news:1160512470.107776.32410
@c28g2000cwb.googlegroups.com:

I've got 2 options - the easy one - disconnect the wire - is an
overspeed really necessary or useful??
Try and get a device to divide the frequency.



As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.

Spinning an alternator so fast DOESN'T make it put out another amp....

No, you can't charge the house batteries in 5 minutes, either....(sigh)


--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.
Spinning an alternator so fast DOESN'T make it put out another amp....

COMPLETELY INCORRECT - look at the output curve for the alternator here
-
http://www.prestolite.com/images_alt...161U_curve.pdf

At engine idle, alt will be at 2500 and deliver 85A. With old pulley
off original alt, alt is only at 1500rpm and output is only 35A - so
quite a useful increase.

Output therefore CLEARLY varies considerably with speed and the spec
sheet I got from Prestolite has it continuously rated for 8000 rpm - so
it is not being overspeeded.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

No, you can't charge the house batteries in 5 minutes, either....(sigh)

At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.

Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

"CS" wrote in message ups.com...
As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.
Spinning an alternator so fast DOESN'T make it put out another amp....

COMPLETELY INCORRECT - look at the output curve for the alternator here
-
http://www.prestolite.com/images_alt...161U_curve.pdf

At engine idle, alt will be at 2500 and deliver 85A. With old pulley
off original alt, alt is only at 1500rpm and output is only 35A - so
quite a useful increase.

Output therefore CLEARLY varies considerably with speed and the spec
sheet I got from Prestolite has it continuously rated for 8000 rpm - so
it is not being overspeeded.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

No, you can't charge the house batteries in 5 minutes, either....(sigh)

At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.

Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

I'm lost - I have not mentioned transformers???

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

Yes, a 10 pole alt at 8000 rpm is generating AC at around 1332Hz. More
A can be produced at 1332Hz than at 50Hz.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

I was explaining why aircraft sometimes use 400Hz AC -- because they can carry
smaller transformers.

I won't disagree that you can generate (not transmit) more power by spinning the
alternator faster (up to a limit).

"CS" wrote in message ups.com...


Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

I'm lost - I have not mentioned transformers???

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

Yes, a 10 pole alt at 8000 rpm is generating AC at around 1332Hz. More
A can be produced at 1332Hz than at 50Hz.