tom opines:

-Something just occurred to me. I wonder if the field is collapsing on him.
Twenty volts is almost like a left over residual charge - it may not be the
rectifier at all.-

Bilge-That's why I want to know if his undervoltage is with "stripped
boards"...I've seen bad grounds knock the shee-yot out of the line voltage,
though. And in 10 years of experience, I've usually found the problems to be
"downstream" from the gennie.

Had an emergency gennie once showed a dead ground on one phase with a totally
stripped circuit board....hmmmm, turns out it was one of the flourescent lights
that provided illumination to the emergency switchboard. That was a kick in the
head...I was almost fixin' to go after the ground lamp socket itself.

If his generator isn't receiving proper excitation voltage to the field, that
would do it also...no DC current, no electromagnet, no electromagnet, no lines
of force for the rotor to break...no, or little output voltage.

Regards;


Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi

I get the same readings with or without a load.
"Bilgeman" wrote in message
...
egavasm:

-The generator I have is an 8kw 8-omdkd-3r-1b diesel serial # D850759014
it's
type is "a Revolving Field, 4-Pole, Brushless" I bought it used 3 years
ago
and it has run fine the whole time. I have a parts catalog which shows the
generator assembley and while there is a rotor, stator and excitor, and
rectifier I do not show any brushes per se.-

Bilge- Are you undervoltaging without load?

G'luck


Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi

wreckless1 wrote:

I get the same readings with or without a load.

Stupid question, but ..

When you tested it with a load - did the load work?
Are you measuring the voltage with something other than the generator
voltmeter (or boat meter)?

Just wondering if maybe the meter is bad.

Eisboch

egavasm relates:

-I get the same readings with or without a load.-

Bilge- Okay, and I assume that you are using a Digital Multimeter to read this.
Eisboch raises a valid question.

If you don't have one, I highly recommend my best friend, a Fluke 77 DMM.
Cheap meters are dangerous and a waste of money.

So...tell me about your voltage regulator...do you have a manual voltage
regulation knob? Or is it one of those solid state arrays?

It'd also help no end to know the excitation voltage of your genny. Voltage is
a function of how intense the magnetic field whose lines of force are being
broken.

I'll wager that in your gennie, the rotor is the electromagnet, and the stator
is where your grid is connected to.

Since you assert that you have no brushes on the critter, I'm assuming that
you have no slip rings, so the rotor is excited by an amplidyne.

We're hoping that your booger is in the external field excitation circuit, not
in the windings themselves...that might be...bad.

BTW, your gennie does have an anti-condensation heater in it, yes? A simple
heat strip or "burger light" can help you avoid no end of truly nasty
hemmorhoids. I've raised resistance to ground on crane motor-generator sets by
orders of magnitude after "baking" the puppies for 24 hours -from 1.5 megohms
to ground,(panic soon time!) to 500 megohms...saved the company a whole heapin'
****load of cash...none of which I ever saw, btw.

G'luck;


Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi

I was reading up on brushless generators and recall the OP said he had a
4 pole system.

According to what I read, (should have bookmarked the URL) 4 pole
generators have a bonded or common neutral and is designed for use with
GFI protected loads. 3 pole generators do not have a bonded neutral.

I'd recommend checking your GFI's and also see if there is a large
"master" on the gen output.

Eisboch

wreckless1 wrote:

thanks for the input but the generator is an ac marine generator which is
brushless and uses a rectifier instead to produce the voltage.
"Chris Newport" wrote in message
news:3914557.aCFQic5eeO@callisto...

On Sunday 24 October 2004 7:44 pm in rec.boats wreckless1 wrote:


The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone
have
any idea of the probable problem? It was running fine and suddenly
stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

Check the brushes in the alternator.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.





An 8 kw genset most likely has brushes - riding on slip rings not a
split commutator. If it is truly brushless, it will probably require
disassembly to have all field & armature winding connections/brazings &
circuits checked. Have you checked the exciter circuitry?

Rob

On Tue, 26 Oct 2004 13:05:11 -0400, Eisboch
wrote:


I was reading up on brushless generators and recall the OP said he had a
4 pole system.

According to what I read, (should have bookmarked the URL) 4 pole
generators have a bonded or common neutral and is designed for use with
GFI protected loads. 3 pole generators do not have a bonded neutral.

I'd recommend checking your GFI's and also see if there is a large
"master" on the gen output.

Ohhhh - nice.

That could be it.

All the best,

Tom
--------------

"What the hell's the deal with this newsgroup...
is there a computer terminal in the day room of
some looney bin somewhere?"

Bilgeman - circa 2004

Eisboch relates:

-According to what I read, (should have bookmarked the URL) 4 pole generators
have a bonded or common neutral and is designed for use with GFI protected
loads.-

Bilge- I would hope that he doesn't have a "hot" neutral, not only do I NOT
like hot or floating neutrals, O best beloved, but they are illegal in merchant
service...and I've no reason to believe that they are legal on small stuff.

I've been "kissy-huggied" more n' once ashore from a neutral line feeding back
voltage and exciting my mental electrons. And shoreside electricians who come
out here are similarly tied in knots..."whut'd yumean 'don't trust colors'?"

What they prolly do is have 3 phases from 3 poles, and they ground the fourth
pole

Could be wrong...always willin' to lurn, especially when it's someone else
getting shocked.

Regards;


Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi

On 27 Oct 2004 01:52:24 GMT, (Bilgeman) wrote:

What they prolly do is have 3 phases from 3 poles, and they ground the fourth
pole
==================================

3 phase power would be unusual in my experience except on a mega
yacht.

wayne relates:

-3 phase power would be unusual in my experience except on a mega yacht.-

Bilge-I had considered that, but Brother egavasm didn't tell us how big a craft
he has, IIRC.

If that's the case, then they've prolly paralleled the poles 2x2. That would
give ya a simple 2 phase output...a pity though, I'm thinking of all the motors
requiring start capacitors for the torque...that's what makes 3 phase so
nice...smaller motors for a given job, and starting torque is no problemo, You
would need step-down xfmrs for your domestic service, and I unnastand that
y'all are a little cramped for room,(heck, WE'RE cramped for room, and we're
700 feet and change long!),but xfmrs don't have to be all that godawful
humongous.

In any event, a moot point if he's not exciting his field...no matter how his
poles are wired, if he's not cutting magnetic lines of force, he's just
spinning a lot of copper.

Regards;


Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi