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Author Topic: Single phase generator alternator  (Read 5814 times)

rosietheriviter

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Single phase generator alternator
« on: October 05, 2007, 04:17:40 PM »
I have an Onan welder/generator model CW251-C, 220V 10KW generator, 350 amp 78VDC welder that was manufactured in 1956.  I originally thought it was a Koehler, but I was mistaken.  Runs like a top, 2 cylinder, air-cooled, gasoline powered, 30+PSI oil pressure, 90PSI compression.

I inquired some time back about my concerns over the starting circuit being Positive Ground, but have since put that part out of my mind.  The starting circuit is not even needed - the engine uses a magneto and has a 6 volt starter.

My questions now are about the generator and alternator. 
The alternator is close coupled to the engine and when the gen/weld selector switch is in "power" mode the engine runs at 1800 RPM.  Voltage and frequency are a product of RPM and are not regulated otherwise on this unit.  4 pole with 2 slip rings.

The generator is on the same shaft (one piece shaft) and when in "weld" mode, increases the throttle (governor) setting to 2300 RPM giving a rated output of 350 DC Amps with an open circuit max of 78 volts.

It has a fairly small bridge rectifier, a fairly large transformer and 3 coils that are maybe one inch in diameter - 6-8 inches long with one connection on each end.  The weld/power switch closes two contacts that go to or from the welding control reostat.

My biggest question is - since the unit welds AND will generate 110+ and/or 220+ volts AC (simultanously), without the battery installed, one of the rotating devices must be magnetically excited?  Should I be able to tell if one of the components attract steel (magnetic)?

Does any one know or willing to venture a guess as to whether welding at 1800 RPM (rather than 2300 RPM) will result in a lower than otherwise expected voltage, amperage, or both?  Or is it more likely that the 2300 RPM is required only for the increased power output from the engine?

I fully intend to convert to an 1800 RPM diesel when I get a chance if the above questions can be resolved.

I think I can send pictures of the unit and of the individual components if that would help answer  the question.

Thanks in advance,

Rosie
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Doug

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Re: Single phase generator alternator
« Reply #1 on: October 05, 2007, 09:56:00 PM »
I think thats a CCK engine ( opposed twin? )

Can't tell you anything about the welder.

The engine probably has a tappered shaft.

CK and CCK are great engines, a diesel DJ series will bolt up but also needs a taper shaft.

Doug
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mobile_bob

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Re: Single phase generator alternator
« Reply #2 on: October 06, 2007, 07:31:14 AM »
Rosie:

to answer part of your question, yes it will weld, but at reduced open circuit voltage and a marked reduction in current
the engine being a gasoline unit does not have a flat a torque curve as a diesel, so the hp falls off rather quickly
however.
we can determine from its 10k AC generator section, that it has enough power to provide for approx 10kwatt of power
so i would expect that it will weld up to about 333 amps at 30 volts in theory, but likely it will be well below that
but i would think it would still do a couple of hundred amps anyway

not many folks have a need to go much over 150amps anyway, unless you are welding with some heavy rod on some really heavy
plate.

with the twin, if it is an onan,, i doubt it would ever get up to 350amps anyway,,
most of the onan twins were put on 225amp machines and ran at full rpm to do that as well.

to do 350amps real well would require about 25 to 30hp in my opinion

i have a small miller 1E that is about 40 years old, it has a single cylinder kohler 12hp and does 160amps tops
it is a dual rpm setup 1800 for AC generation 3500watts, and 3600rpm for welding

it will weld at 1800 but at a dramatically reduced ampacity and lower open circuit voltage, which makes striking the arc
difficult.

i gotta ask,, what do you plan on welding that would require that much ampacity?

bob g
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rosietheriviter

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Re: Single phase generator alternator
« Reply #3 on: October 07, 2007, 12:03:20 PM »
I think thats a CCK engine ( opposed twin? )
Can't tell you anything about the welder.
The engine probably has a tappered shaft.
CK and CCK are great engines, a diesel DJ series will bolt up but also needs a taper shaft.
Doug

Thank you, Doug. 
That is great information for me. 
The CCK is supposedly an"improved" version of the CW but without access to manuals (I've searched extensively), that is academic.
 
Rosie
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rosietheriviter

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Re: Single phase generator alternator
« Reply #4 on: October 07, 2007, 12:20:24 PM »
Rosie:

to answer part of your question, yes it will weld, but at reduced open circuit voltage and a marked reduction in current
the engine being a gasoline unit does not have a flat a torque curve as a diesel, so the hp falls off rather quickly however.
we can determine from its 10k AC generator section, that it has enough power to provide for approx 10kwatt of power
so i would expect that it will weld up to about 333 amps at 30 volts in theory, but likely it will be well below that
but i would think it would still do a couple of hundred amps anyway
not many folks have a need to go much over 150amps anyway, unless you are welding with some heavy rod on some really heavy plate.
with the twin, if it is an onan,, i doubt it would ever get up to 350amps anyway,,
most of the onan twins were put on 225amp machines and ran at full rpm to do that as well.
to do 350amps real well would require about 25 to 30hp in my opinion
i have a small miller 1E that is about 40 years old, it has a single cylinder kohler 12hp and does 160amps tops
it is a dual rpm setup 1800 for AC generation 3500watts, and 3600rpm for welding
it will weld at 1800 but at a dramatically reduced ampacity and lower open circuit voltage, which makes striking the arc
difficult.
i gotta ask,, what do you plan on welding that would require that much ampacity?
bob g

Thank you, Bob. 

That sounds logical to me, just looking for an educated opinion.   The machine is rated at 20 hp, some 46 amps @ 220 VAC @1800 RPM.
I'll just disable the 2300 RPM throttle adjustment, leaving the 1800 RPM setting. My "fix" will be reversable, so trying will lose nothing but some time.

Striking an arc, that is no real big problem for me, Daddy taught me how to weld by using his old rod stubs and with rod that had the coating damaged or missing. 
It was a real treat when he let me use "new" rod.

I do not expect to do much welding at all.  I have never welded at settings above 125 amps except when Daddy showed me how to run 3/16" E7028 in a flat position only.  Seems like it was around 375 amps or so and the welded metal warped very badly if it were not welded or clamped in position.

My personal choice is 3/32" E7014 at around 75 amps - makes an extremely pretty weld.  I use 3/32" (80 amps)or 1/8" (110 amps) E7018 for some "out of position"or E6010 for some "dirty metal" welding.

Rosie
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rcavictim

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Re: Single phase generator alternator
« Reply #5 on: October 07, 2007, 01:17:17 PM »
In my experience 7014 is the best general purpose, all position ac or dc rod going.  If you only want to stock one kind, that would be my choice no question.  Gives the best results I have seen from stick welding on an AC buzz box.

If you have a DC machine you can forray into other types and enjoy less splatter and improved penetration and heat control by polarity selection.  7018 is a good, very strong DC rod used for industrial construction where strength is important.

7024, a flat only rod has much iron fill in the flux and is good for building up.  I use it for buildiing up worn shafts, or on thinner sheet metal where minimal penetration is important, like welding to a pressure tank (careful!).

For attaching nodular iron like black iron plumbing pipe fitting, or mild steel like automotive exhaust pipe to a cast iron exhaust manifold outlet  I use 308-16 stainless stick rod and chipping hammer. Bzzzzzt...bang bang bang.....bzzzzzt....bang bang bang, repeat as necessary.  Preheat the cast iron if possible and let air cool out of drafts.  No splashy cold water to cool quickly!
« Last Edit: October 07, 2007, 01:27:13 PM by rcavictim »
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Doug

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Re: Single phase generator alternator
« Reply #6 on: October 07, 2007, 05:19:24 PM »
I don't know anything about the CW ( not even sure I ever seen one )

The CK and CCK were real work horses, I've seen them in forklifts, pumps generators. That engine and the Wisconsin V4 are the two most reliable and long lived gas sationary type engines I know of.

I did see an older Onan single from the 40's some years ago ago that was still providing lights and power. It used an electric choke of an old Chrysler and generator for sarting and recharging batteries. The owner made these modifications but it all worked so well I could have been fooled into thinking that he way they came.

The Onan CK and CCK also used a ball bearing govener system I think is better than most fly weight types out there. Weaknesses oil seals ( like all engines ) and the points and condensor. The carburator on some were a Carter model N but just about anything can be bolted on if its the right size. These engines tollerate an improvised repair ( made a govener linkage and carb with parts from a 71 series detroit linkage and JD snow blower carb once ).

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rosietheriviter

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Re: Single phase generator alternator
« Reply #7 on: October 14, 2007, 02:09:51 PM »
I'll be off-line for the next 30 days but hope to see more information when I return.

See ya'll around 11/15/07

Rose is Rose
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