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Generator trouble - help Options
Pat Miketinac
#1 Posted : Monday, October 26, 2009 4:15:19 AM
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My first guess would be worn brushes, but I don't know that gen. The guys at otherpower.com probably know, see their discussion board.

LaserBillA
#2 Posted : Tuesday, October 27, 2009 7:12:17 AM
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If it's a brush type unit then start with the brushes. Otherwise it's hard to say.

First you have to keep in mind that both brush and brushless generators work like an alternator on a car. You have to send power to it in order to get power out. This means that it can also be from a bad 12 volt battery.

Brushless units have just enough of a perminant magnet to create a 12 volt source and then they use that 12 volts to send pulses to the other windings to charge the core. The core itself has windings, a diode bridge and a capacator. Once the capacator charges it works just like a brush type.


general info on generators
http://en.wikipedia.org/wiki/Electrical_generator

http://en.wikipedia.org/wiki/Alternator

davisonh
#3 Posted : Friday, October 30, 2009 3:00:11 AM
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Ok,electrician to the rescue here.From what you have told me and the star,pentagon diagram you describe,what you have is a 3 phase generator set.First thing I would do is take your meter and see if you get 120 volts from each hot line to the case of the generator.You have 3 hot lines.Next thing I'd check is the neutral connection.(the white or natural gray wire) If thats loose either in the generator or at the house connection that'll cause your voltage to go haywire.Most 3 phase generators are of the revolving field type which means the exictation current is delivered to the rotor of the generator.It is a rotating electromagnet which induces your main electrical current in the stator of the generator.There are 2 slip rings delivering 'charging dc' to the rotor.All 'brushless' generators have these brushes,lol.If these brushes are worn that'll also cause the voltage to go low.And lastly make sure your load is balanced between all three phases .Loading down two phase legs will drop your voltage.If it is not any of these then it may be a loose connection to the windings of the stator(the fixed coils in the generator)ake a resistance check between any two out of three phases with the generator off.The reading should be around 3 to 12 ohms between hot legs,if you get nothing then there's an open wire in the windings somewhere,that means rewinding.If the resistance is too high then your windings are burning,look at the stator coils and see if they;re black,burned looking at all,then the generators' toast.Hope this all helps jd,lemmee know how you make out.

jd
#4 Posted : Friday, October 30, 2009 6:29:20 PM
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Davisonh, boy am I glad to see you!  But, in the meantime, I have gone hogwild!  Perhaps a bit too far.  Imagine a steel framed box, 4 x4 x 2 feet.  It is framed by 2"angle steel and clad in heavy sheet metal.  Inside is a genset unit comprised of a 34 hp diesel Isuzu and a Fidelity 'back end' (what do you call the back end?  Alternator?).  The !*&%$ frame makes it almost impossible to get at some things and, of course, the rear mounted 30 gallon fuel cannister is mounted against the side that allows access to the control box.  I, naturally added to the structural complexity by adding a 100 gallon fuel tank with its support legs also in the way.  The unit is built by Klinge and they have website.  The unit looks like their modern 15 kw 'betwen-the-rails' model.  Not quite - but close. 

So, yesterday, I went at it and removed the 100 gallon tank, the cannister tank and other access problems.  But the unit still weighs 2500 pounds and so I jacked it up, put pipes underneath for 'rollers' and moved the assembly into the middle of the genset room to afford access.  Getting into the black box (at the back of the back end) was difficult.  It simply would not come off because of the steel frame is in the way.  Out came the mini grinder with a razor cut and I 'cut' the top off the box and the then the back side would come away.  I covered the box guts with cloth to prevent metal shavings getting in.   I now have pics of the beast's butt.  It's like looking at the wrong end of a baboon. 

Back to the problem........my voltage meter reads 180 volts at 60 hz.  But my Outback inverter rejects the power as 'too low voltage'.  And, since I am only sending 120v to the inverter, the problem is likely with the 120 circuit.  I get 120 by centre-tapping between L1 and L2.  My problem?  For starters my Multimeter (which I don't know how to read properly) is broken.  Secondly, because the 240 volt meter was reading 180, I went to the heart of the beast.  Maybe I should have simply done something else.  But I did check all my wiring to the point of the black box and everything seemed OK.....................anyway, I went the whole nine yards.  I can now see the Fidelity back end but all the tanks and things are in a heap.  I doubt that I could run the machine for more than a minute (I took all the fuel out of the tanks). 

So, first question - want me to send you pics of the back end?  I am at jdavidcox@hughes.net.  Second question - was there something I could have checked without disassembling this monster?  Thirdly (it is a monster) what would it cost (roughly) to rebuild the back end ata windings shop?  I suspect that it needs it.  Mind you, there are two halves to the backend.  There are the main windings in the big round housing and then there is the control box at the very back.  By the way, I cannot find an AVR.  I have more questions but that will help.

And thanks for showing up!!!!!

davisonh
#5 Posted : Saturday, October 31, 2009 3:11:55 AM
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Yes jd,I think that'd be a good idea.I'm >davisonh1@hotmail.com">. Um,I hate to see you going thru all that work,but basically all you need to do is get the endbell off the generator end.Usually four bolts holding the bell  end on.Can't tell till I see your pics,then I'd be able to give you a better idea of what to do.You'll be able to tell whats wrong pretty much right off the bat once the bell ends' off.If theres a burned out winding you'll see it right off,it'll be a blackened coil(or more than one blackened coil)and most likely you'll smell it too.Smells like burnt plastic or varnishy kind of smell.I call it bakelite burn smell,can't miss it.Now question I have,is there a coupling of some  sort between the engine and the generator? Sometimes the crankshaft and the generator shaft are one and the same,if it is you have to send the whooole thing out to be fixed though I have taken the stator as a unit off and left the rotor hanging on 2 x 4 blocks.Ya the inverters doing its job,telling you it's supply voltage is too low.You say this is a 3 phase generator,if it is L2 will be a live line not a grounded line.Is there an L3 by chance?It should be L1,L2,L3 and N if it is 3 phase.If not it'll be L1,L2 and N.N has no power on it,L1 and L2 are live lines.N should he white or gray.Did you check fuses and circuit breakers?L2 on a 3 wire or a 3 phase circuit should read 240 volts between L1 and L2.Try going between L1 and the green wire connection or the case of the generator,with the setting on resistance.There should be a small resistance reading there.Then do that between L2 and then L3.Should be a small reading.No problem,if you need assistance I check my email every day.The star you mentioned in the diagram tells me you have  3 phase parallel connected windings ,it can be connected either in parallel or series,but I won't go into that in depth.That gets confusing.Out of the middle of the star connection there should be a wire shown,thats your neutral wire.(the wire with no power on it.)That needs to be connected to the case of the generator somehow.Alright,I'll wait for your pics and get back to you.Good luck!

LaserBillA
#6 Posted : Thursday, November 05, 2009 9:52:42 PM
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Finding a schematic is quite useful. I'm glad that the 15Kw 1950's generator I bought came with the manuals and schematics.

The larger generators are also designed so that you can remove the brushes without taking it all apart... So before you go to all the trouble look for large ~1 inch screwdriver slot plates in the outer case.

davisonh
#7 Posted : Thursday, November 05, 2009 11:39:05 PM
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Hey Bill,you're right but the newer alternators don't even have brushes on  slip rings anymore,they use the diode trick.They don't do away with the DC generator at the end but what they do do is either wind a small ac winding into the alternators' main stator or use a transformer tapped off the stator mains to run thru a diode bank/power resistor setup to keep the residual/active magnetism up in the DC field coils.Then what they do is take the CEMF developed on the DC armature and run it into the AC rotor(both are on the same shaft) neccesary to set up the dc rotating magnetic field that generates the heavy power current in the main stator windings.Pretty neat trick The voltage regulation is set by the tapped power resistors hooked into the DC field coils and of course the frequency is set by the speed of the engine,so it does away with the need for a field rheostat.I've even seen em with the DC coils on the inside with the AC stator wound 'around' the DC magnet coils.

jd
#8 Posted : Saturday, November 07, 2009 7:05:29 PM
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Wahoo!  Genset running!  Turned out to be diodes in the rectifier.  Had to cobble a few together by way of adapting and such but replaced the dead ones with new ones (slightly bigger) and it works!  There definitely is a God and he makes allowances for fools, infants and guys who work with electricity.  Yahoo!

'Course, I have day putting everythng back together but man, oh man, this feels good!  Looking at the back end of that generator was like looking up a baboon's butt.  Not pretty.  And way more confusing than one would think.  I felt like a proctologist!

 

Anyway, Davh.........thanks for being there.

 

dc

davisonh
#9 Posted : Sunday, November 08, 2009 4:38:41 AM
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No problem jd,glad I could be of help...only thing I could suggest is to balance out your house power load on all three phases;that diode(s) problably burnt out either because of age or too much current load on one diode set;they heat up after awhile and burn out.When you have even current load on all 8 poles of that DC magnet the diodes don't heat up as much.Anyways I am glad it worked out and hey now you have an idea about how the whole thing works and I think thats the most important of all!

jd
#10 Posted : Sunday, November 08, 2009 7:27:09 PM
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Don't give me too much credit, Dh.  I still have no idea how it all works.  Maybe some partial,  vague................nah................I know nothing.  I still have trouble with the concept of alternating current.  So, no credit, please.  Luck and finding what looked like diodes was the key. 

And yes, I agree, I have to balance the load.  Which brings me to the post just below - finding a good (affordable) battery charger.  Loading up one side with a 240v battery charger putting out 60 amps at 48 volts would balance it.  While I was at the baboon's butt (generator end) I continued on and I 'split' one 240 phase into two 120's (previously I was running off just one 120) and have dedicated one of the 120 circuits to just the washing machine.  So that will help. 

The reality is I don't need 15kw.  I need 7.5.  But you work with what you have............right?

davisonh
#11 Posted : Sunday, November 08, 2009 10:54:47 PM
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Exactly..and the extra capacity can't hurt either.Yes that should help a lot.Now the current load will be evenly balanced.

jd
#12 Posted : Sunday, November 08, 2009 10:54:47 PM
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Isuzu engine powering a Fidelity 15kw generator.  All of a sudden the inverter rejects the power.  Upon checking, my genset has reduced from 240 volts to 180 volts??!!  Not the engine - still putting out 60hz at 1800 rpms.  Definitely the generator.  May be the voltage regulator (wherever that is) but why all of a sudden?  Suspect one 'terminal' of power.  This unit has some kind of 'star' or pentagon like arrangement from which power is taken from each point.  Combine just two and you get 120, combine three and get 240...........or something like that............electricty is not my strong suit.  OK, I do not have a strong suit but being critical doesn't help.  I am about to dig in and start taking things apart...............always a bad move when you have no idea what is in the black box.  Davisonh..............you there?

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