# Your 6000 watt gen only puts out 3000 watts...



## LincTex

....of 120 volt power per "side".

Only 240 volt loads can use the full capacity. It is because the generators are wired as "synchronous", like two 2-pole generators running side by side in the same shell.

Here is the website for this info: http://www.utterpower.com/synchronous-generator-basics-simple-guide-to-rewire-your-head/

Here is a why. In this picture, you can see that only one half of the generator windings run one 120 volt outlet, while the other half runs the other outlet.
http://www.utterpower.com/wp-content/uploads/2011/11/Coleman-Gen-main-Parts.jpg









So, if you want to start up a large-draw 120 volt item like a well pump or other large power tool, the one side (half) of the big, expensive generator you bought might not have the capacity to do that.

So, if you use a multimeter and measure carefully, you can wire up the windings *IN PARALLEL*, so that you can still use 120 volt power, but at DOUBLE the amps.http://i1225.photobucket.com/albums/ee391/lawrosa/generator/genrewire.jpg









You can wire in a switch to give either the original configuration, or both windings in parallel:









9 years ago I got a Harbor Freight 3500 watt 6HP gen and couldn't figure out *WHY* a generator that size couldn't handle loads that were about half it's rated capacity. If you are like me and have been mystified as to why you can't run a piddly little air compressor from such a large generator, now you know why! With this mod, you can get FULL RATED capacity from your generator on 120 volt loads!!


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## machinist

Can this cause a phasing problem? I don't know how they are wound, but if the 2 windings are not in phase, it looks to me like that could cause trouble.


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## LincTex

machinist said:


> Can this cause a phasing problem? I don't know how they are wound, but if the 2 windings are not in phase, it looks to me like that could cause trouble.


Possible - worst case scenario, you would have to switch one black & one white.

Use an ohm meter with the engine off to find common pairs and tape them together. Then start the engine, measure between the wires from each common pair to the other common pair. The lowest voltage ones get matched up.


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## MrDean

The simplest solution is to purchase one of those 120VAC to 240VAC transformers that are used for running a 240 Volt well from an inverter. You simply wire the 240 Volt generator out put to the 240 volt side of the transformer and you get 120 Volts out, the 240 volt input will be balanced and you can get the full generator 120 Volt output.

I have one that runs my well 240 VAC submursable pump from my Xantrax 5548 Inverter. I use another on on the output of my 8KW Generac Propane Auto-Start backup generator to provide 30 Amps of 120 VAC for input into the Xantrax inverter battery charging portion.

Another point that many do not realize is that one must de rate a generators output 4% per 1,000 ft elevation due to the lower air pressure resulting in the lowering of the Horse Power a corrosponding amount of the generators motor whether it be Diesel, Propane or Gasoline.

Here is the transformer as I was wireing it up to the 8KW generator










Here it is after I finished the instillation, works beautifully and easily balances the 120 Volt output of the generator.










In this picture you see the Trace 120 to 240 transformer used for the well, the grey oblong box just below the inverter.










I can answer more questions if anyone is interested.


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## MrDean

An additional note, 

Living at 6,300 ft elevation, we de rate our generator 25% ie, a continous output rated generator of 5,000 watts is only good for 4,000 watts.

Another caution especially on lesser expensive generators youu will see a certain rating like it is a 5,000 watt generator, but be careful that you understand that you are reading its continous rating, and not its higher surge out put rating. Running a well or anything with an electric motor on a not quiet big enough generator causes a low voltage situation which causes the amperage to rise with the result of a greately shortened life or simply ruining the motor in what you are oporating. Higher than normal amperage creates excessive heat which severe damage.


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## LincTex

I have been looking.... every now and then I'll see .5Kva to 1Kva 2:1 transformer on eBay for pretty reasonable (less than $50), but the larger ones are always over $100. I'll re-wire the plugs and save the $$$.

I would LOVE to use a 2:1 to step up to 480 volts for lots of the farm when on Gen power, and back down to 240 volts where the work is being done (well pump, etc.). Maybe I'll stumble upon some decent price TxFrmrs someday.


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## Jimmy24

LincTex said:


> I have been looking.... every now and then I'll see .5Kva to 1Kva 2:1 transformer on eBay for pretty reasonable (less than $50), but the larger ones are always over $100. I'll re-wire the plugs and save the $$$.
> 
> I would LOVE to use a 2:1 to step up to 480 volts for lots of the farm when on Gen power, and back down to 240 volts where the work is being done (well pump, etc.). Maybe I'll stumble upon some decent price TxFrmrs someday.


Having worked a good bit with all forms of secondary voltage through 30 years with an electric utility, I can speak to a bit of this.

You do realize there are two different types of 480 electric services, correct? There are the standard 277/480 Y services and there are the straight 480 corner ground type services. Plus both are 3PH. Are you planning on using a converter for single to three ph? I doubt your genset will run the corner ground version. That is for high amp conditions, mainly large wells. Just saying.

I accomplish the hi amp usage of my 3450 watt genset with a small and somewhat old 50 amp use box. I simply bring the 30 amp 240 volts into my box. Split it there into boxes mounted below it at 120 volts. They run my fridge, 10k BTU window rattler and some lights with no problems. I never use the 120 outlets on the unit.

Dry cell transformers are fairly reliable. We used them quite a bit to give customers full 240 volts on bad underground services.

Good luck and be careful with that 480.

Jimmy


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## LincTex

Jimmy24 said:


> Plus both are 3PH. Are you planning on using a converter for single to three ph?


No... Not at all. 240 single phase stepped up to 480 single phase - - out to the load, back down to 240 volts again (or even 120). I never mentioned 3 phase.

I do have some 3-phase on my place, but it is all within the shop - and I make it there from single phase power, a 3-phase motor and capacitors. I don't have anything "out and about" that is 3-phase powered.


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## MrDean

Both of my step up/step down transformers are in the $300.00 to $500.00 range as they are very heavy because they are wound with Copper. I think it is always less expensive in the long run to use hi quality equipment.

We have lived 100% off grid for 16 years with out a single failure or interuption, granted I have upgraded the system three different times in the past. Currently we have 3 refrigators, one with an ice maker plus a chest freezer, a 60" TV, 3 46" TV's and one 32 ", all hooked up and working, nine 52" ceiling fans, two elect coffee pots, two microwaves and lots more. My back up gen set only has run 4 hours in the last two years, the nearest Utility power is 2 miles away.


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## MrDean

We don't run everything all the time of course but what ever is needed is running with out worry.


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## Jimmy24

LincTex said:


> No... Not at all. 240 single phase stepped up to 480 single phase - - out to the load, back down to 240 volts again (or even 120). I never mentioned 3 phase.
> 
> I do have some 3-phase on my place, but it is all within the shop - and I make it there from single phase power, a 3-phase motor and capacitors. I don't have anything "out and about" that is 3-phase powered.


Sorry, I now understand what you want to do. I would say though that even at 480 for your mini transmission line, the load needs to be pretty small. Your line losses and losses through stepping up and then stepping down will be pretty high, particularly at that voltage. And though 480 is twice the voltage, it will shed voltage at a high rate. Larger conductor will be required.

Just wondering that's all. Good luck.

Jimmy


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## Jimmy24

MrDean said:


> Both of my step up/step down transformers are in the $300.00 to $500.00 range as they are very heavy because they are wound with Copper. I think it is always less expensive in the long run to use hi quality equipment.
> 
> We have lived 100% off grid for 16 years with out a single failure or interuption, granted I have upgraded the system three different times in the past. Currently we have 3 refrigators, one with an ice maker plus a chest freezer, a 60" TV, 3 46" TV's and one 32 ", all hooked up and working, nine 52" ceiling fans, two elect coffee pots, two microwaves and lots more. My back up gen set only has run 4 hours in the last two years, the nearest Utility power is 2 miles away.


Oh yes I agree. We used copper wound cells as well. One might have to leave on on all weekend and full load of a home.

I admire your off grid life style. Do you use any solar or wind power along with your genset?

Jimmy


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## MrDean

Jimmy, the Gen Set is only used as a back up and is rarely needed for that, ie only 4 or 5 hours in the last 2 years.

We have 4,000 watts of Solar Panels running thru a Xantrax 5548 inverter with a 24 2Volt L-16 size battery bank.

Click on this for more pictures and explanations as we have put our place on the market.

http://showlowarizona.blogspot.com/

Also have it listed in the For Sale section in this forum


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## Jimmy24

MrDean said:


> Jimmy, the Gen Set is only used as a back up and is rarely needed for that, ie only 4 or 5 hours in the last 2 years.
> 
> We have 4,000 watts of Solar Panels running thru a Xantrax 5548 inverter with a 24 2Volt L-16 size battery bank.
> 
> Click on this for more pictures and explanations as we have put our place on the market.
> 
> http://showlowarizona.blogspot.com/
> 
> Also have it listed in the For Sale section in this forum


Thanks!! VERY cool.

Jimmy


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## LincTex

Let's see if the rewire schematic comes up:
http://s1225.photobucket.com/user/lawrosa/media/generator/genrewire.jpg


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## labotomi

I'm not trying to argue, but having spent a lot of time operating a distribution system that included several large generators in parallel, I see something that could become a problem... possibly a large one.

What you're effectively doing is producing the same effect as running two generators in parallel. The problem is that these "two" windings/generators are not designed to operate in parallel and have no way to ensure the separate windings are sharing the load equally. Even with them in parallel one winding can and probably will be carrying most of the load.

When running generators in parallel it's possible to create circulating currents between the generators. Rewiring the generator in this fashion can produce the same thing. This can happen with the individual windings as the one with the higher voltage will force current into the one with the lower voltage output which is a bad situation for both of them. This doesn't mean it will absolutely happen, but without being able to separately control the voltage of each winding with a built in "droop" it's very possible.

It's also possible for a single winding to be carrying 100% of the load until it becomes overloaded and the voltage drops below that of the winding that's not carrying load. The winding with the lower voltage will still only carry that portion that the overloaded one can't meaning the first winding will continue to be overloaded.

Here's a document addressing the parallel operations of generators and how a drooping voltage characteristic minimizes the chance of circulating currents. This just means that the voltage output of each generator decreases slightly with increasing loading.
*http://esrdc.mit.edu/library/ESRDC_library/VR_parallel.pdf
*

Also, maybe you already knew but the 240v outlet will only have 120v when wired in the modified configuration.


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## Viking

I talked to a friend that is an expert on generators as I have been considering pulling the propane fueled 6.5 Onan out of our motorhome and using it for a backup power supply for our home and I asked him about rewiring it to have 120/240 because I figured that the generator was parallel wired for just 120 VAC and he told me it could be rewired for split phase. So what LincTex has shown is on right. Sadly, generators build nowadays are for the most part 3,600 rpm screamers which are very noisy and not kind on the engine or gen bearings. The motorhome gen runs at 1,800 rpm and is very quiet. From what I've seen on most of the newer generators is you get what you pay for and most are like Yugo's, junk to begin with.


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## labotomi

Viking said:


> I talked to a friend that is an expert on generators as I have been considering pulling the propane fueled 6.5 Onan out of our motorhome and using it for a backup power supply for our home and I asked him about rewiring it to have 120/240 because I figured that the generator was parallel wired for just 120 VAC and he told me it could be rewired for split phase. So what LincTex has shown is on right.


I'm not saying you can't do it. I'm saying it may cause problems and shorten the life of the generator.

This statement by LincTec is essentially correct. Parallel operations of generators isn't simply connecting the wiring together. There's a lot more that goes into the design and operational procedures. 


LincTec said:


> It is because the generators are wired as "synchronous", *like two 2-pole generators running side by side in the same shell.*


Something to think about:
If it were this easy to connect the windings for parallel operation it would be easy to connect two or more entirely separate generators in the same way. You could connect two 2000w generators to make the equivalent of one 4000w or any other combination you wish. Even if connecting identical generators it would be a bad idea.

There are generators made with this capability (honda comes to mind) but it's not something you can do with those not specifically designed to operate in this manner.


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## LincTex

labotomi said:


> If it were this easy to connect the windings for parallel operation it would be easy to connect two or more entirely separate generators in the same way.
> You could connect two 2000w generators to make the equivalent of one 4000w or any other combination you wish.


No, I don't agree... and I wouldn't condone that ("two or more entirely separate generators"), for a great number of reasons (unless you could possibly synchronize the voltage regulators like some newer Honda ones do).

The portable gens in this discussion have the windings laid side by side (two in hand, four in hand, etc) in the same stator, so they see the same lines of flux simultaneously. You cannot over or under load one set of windings unless there was a significant variance in resistance between the windings (doubtful, unless connected poorly). Onan generators that can be wired as 120 or 120/240 have been doing this for decades, with no ill effects. (spec 3, spec 1 are only 120 and can't be wired for 240)

There are two very good reasons for doing something like this. 
First, this idea comes from the RV community, which frequently uses one very large 120 volt plug to power the RV. Someone powering an RV on 120 wouldn't need to buy a gen twice as large if they wired their smaller one this way.

Second, a lot of folks have large 120 volt items (like an air compressor or a well pump) that they want to be able to power with their generator, and then wonder why they cannot. This explains the "why". I for one would also like to use a small generator for fuel efficiency at times when I don't want to be limited to just one side of the windings of one that is twice as large as it needs to be.

Yes, you are correct in wiring it this way removes the ability to use the 240 volt plug. I think I mentioned that earlier, but if I didn't I apologize.


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## labotomi

LincTex said:


> The portable gens in this discussion have the windings laid side by side (two in hand, four in hand, etc) in the same stator, so they see the same lines of flux simultaneously. You cannot over or under load one set of windings unless there was a significant variance in resistance between the windings (doubtful, unless connected poorly). Onan generators that can be wired as 120 or 120/240 have been doing this for decades, with no ill effects. (spec 3, spec 1 are only 120 and can't be wired for 240)


I'll agree partially. Even with the stator windings physically side by side there will be slight difference in the resistance, air gap, iron core and laminations. All these can add up causing the differences or it can be close enough that the generator will be perfectly fine. Each generator may be different also.

I'm not saying you can't do it or that it will absolutely cause problems, but it's not something that I would do even with my background which is more comprehensive about this subject than most people who will try this. You have a good background and may be able to recognize if something's wrong, but many who will try this won't.

I'm not familiar with the Onan generators you mention. Is this a built in feature? Do you have a schematic?

I know what the intended purpose of paralleling the windings. It's basically the same as paralleling batteries as in increasing current (and thus power) while keeping the voltage the same instead of it's present setup where the two 120 windings are separate but one side of the each winding connected which allows the windings to be used in series (higher voltage, same current) for the 240 receptacle.

I'm just voicing my concerns. I can see your point and the difference may be insignificant. I work with electrical distribution systems every day, but haven't worked with generators in quite a while, but one of the most important things about controlling generators in parallel was to match the voltages so that the droop circuit would distribute the load in proportion to the machine ratings. It was a small step from proper operation to overloading our generators or turning a steam turbine generator into a steam pump when connected to a source such as the civilian grid which has zero droop on the distribution side.


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## Viking

labotomi said:


> Something to think about:
> If it were this easy to connect the windings for parallel operation it would be easy to connect two or more entirely separate generators in the same way. You could connect two 2000w generators to make the equivalent of one 4000w or any other combination you wish. Even if connecting identical generators it would be a bad idea.
> 
> There are generators made with this capability (honda comes to mind) but it's not something you can do with those not specifically designed to operate in this manner.


 Ah yes, and here is the issue, phase matching. This is where it's so dangerous to just hook up a home generator into your home electrical system without using a transfer switch to isolate generator power from when the grid power comes back on line, phase differentiation. Now if some of the newer generators, like some Honda inverter types, have a connection to match phases then they can work. When I bought my pure sine wave inverter for our standby solar power system I bought one that can be paralleled with up to four of the same kind of inverters. Instead of a standard inverter controller I got a special router that matches phases, whatever small differences there is between inverters really doesn't create a problem. As to whatever small differences there may be in a single generators' windings for 120-120 VAC for split phase 240 VAC as long as the generator is rewired to parallel phase both the 120 VAC outputs there is no real problem. If you don't know what you are doing, leave it to someone who knows. One thing I learned many years ago was from a engineer at a small hydroelectric dam when I asked him about matching phases when a generator was on standby, he told me that in order to keep the generator in phase they motorize it until it's needed to add to kilowatts needed.


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## labotomi

The paralleling of generators manually uses a meter like this.










You match voltages then adjust the frequency of the generators so that the indicator on the synchroscope is turning slowly in the fast direction. This means that the oncoming generator is at a slightly higher frequency than the one already in service. This ensures the oncoming generator picks up a slight amount of load when placed online. The goal was to operate the switch so that the breaker physically shut with the synchroscope at the 12:00 position. It took some time to learn the operating times of the various breaker sizes. I've seen quite a few that opened right back up because the operator shut the breaker with too much phase difference.

As soon as the breaker is shut the generators are in phase. Any adjustment of the speed setting of a generator would then cause an increase of decrease in how much load it was carrying. There is not way for electrically paralleled generators to be out of phase or run at different frequencies.

Contrary to what most people think, it was better on some machines to run one with a high load and another lightly loaded and switch back and forth once a day.


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## LincTex

labotomi said:


> Even with the stator windings physically side by side there will be slight difference in the resistance, air gap, iron core and laminations.


For these to a be a factor, you would have to have some *significant* variances in build quality, and honestly by judging from what I see inside modern generators.... should not be any concern.



labotomi said:


> I'm not familiar with the Onan generators you mention. Is this a built in feature? Do you have a schematic?


I can't really go search for one now, but it's just two sets of windings in the same stator. Twist 2 and 3 together for neutral and 1 and 4 will be 240 volts. If you want 120 volts only at double amperage, twist 1 and 3 together and 2 and 4 together.... that type of thing.



labotomi said:


> instead of it's present setup where the two 120 windings are separate but one side of the each winding connected which allows the windings to be used in series (higher voltage, same current) for the 240 receptacle.


Yes.



labotomi said:


> I'm just voicing my concerns. I can see your point and the difference may be insignificant.


Most likely scenario.



labotomi said:


> but one of the most important things about controlling generators in parallel was to match the voltages so that the droop circuit would distribute the load in proportion to the machine ratings.


Correct, but kind of like comparing a house-cat to a Siberian Tiger. Yes, they are both cats, but they behave a little differently and must be handled differently. The folks reading this thread won't be connecting their generator to the grid, but if their shiny new 10HP Briggs powered 5000watt/6500peak watt generator doesn't power their 120 volt submersible pump, this explains why and shows what they can do to make it work.


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## LincTex

labotomi said:


> The paralleling of generators manually uses a meter like this.... This means that the oncoming generator is at a slightly higher frequency than the one already in service. This ensures the oncoming generator picks up a slight amount of load when placed online.


This is really far beyond what the original intent of this thread was supposed to accomplish. I cannot ever advocate anyone trying to phase together two individual portable generators.

It isn't impossible to do by any means, but it is an entirely different subject than connecting two windings in the SAME STATOR in parallel in order to get a higher amperage at a lower voltage.


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## labotomi

LincTex said:


> For these to a be a factor, you would have to have some *significant* variances in build quality, and honestly by judging from what I see inside modern generators.... should not be any concern.


I usually respect your comments but I do not believe you have ever conducted an inspection that would actually detect these differences. Those differences wouldn't have to be as large as you must think.

I had a reply to the rest of this but it's not worth the effort. Apparently you've found a simple modification that's ok to do that the manufacturers won't provide as a feature even though it wouldn't be expensive of difficult (even if they add killing the 240V circuit when in the "alternate" configuration).


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## labotomi

LincTex said:


> This is really far beyond what the original intent of this thread was supposed to accomplish. I cannot ever advocate anyone trying to phase together two individual portable generators.
> 
> It isn't impossible to do by any means, but it is an entirely different subject than connecting two windings in the SAME STATOR in parallel in order to get a higher amperage at a lower voltage.


It was an informational response to the post above it (that mentioned a hydro-electric dam). You don't need to get defensive about that one.


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## LincTex

I am not actually getting defensive, sorry if my posts sound that way. I always appreciate your technical input. I do enjoy a lively discussion, though!!!!



labotomi said:


> I usually respect your comments but I do not believe you have ever conducted an inspection that would actually detect these differences. Those differences wouldn't have to be as large as you must think.


When is the last time you have seen a modern portable 3600RPM generator stator up close? We aren't trying to generate laboratory grade electricity here... just run an air compressor or well pump, etc. They are not that efficient to begin with, how bad do you think it is really going to get?

I think you are getting confused/riled about acceptable tolerances.

What do you suppose an acceptable tolerance between two synchronous windings in the stator of the common, 3600 RPM two pole generator are? You KNOW they will be fighting each other when connected in parallel.... but you need to understand that even when that happens, it most likely falls within acceptable limits (which are probably pretty generous) of what the tolerance is per winding output.

If you tried to convince me the two windings would be so far out of whack that you would take total a total max output of (example) an 8500 watt peak, 10HP Brigss and knock that sucker down to a peak of 5000 watts max (due to internal losses), I would listen to what you have to say.

But what *IF* you only lost 100 watts? Maybe a 250 watt loss? How about 500? Well, that would be acceptable in this case.

If I needed to run my well, but I could only afford a $599 Home Depot special that puts out a continuous 5500 watts (ideal conditions, LOL) at 240 (half of which is 2750) on one 120 volt outlet, then darn tootin', I'll take a loss if I can re-configure the windings and get say... 4800-5000 watts continuous at 120. that is very acceptable.

3600 RPM two pole units are not that perfect to begin with, how much more "un perfect" would we make one if we paralleled the stator windings, seriously? Onan has been doing this for 50 years, are they really built that much better (well, those of us who own them would agree, but that's another story  )


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## labotomi

LincTex said:


> When is the last time you have seen a modern portable 3600RPM generator stator up close? We aren't trying to generate laboratory grade electricity here... just run an air compressor or well pump, etc. They are not that efficient to begin with, how bad do you think it is really going to get?
> 
> I think you are getting confused/riled about acceptable tolerances.
> 
> What do you suppose an acceptable tolerance between two synchronous windings in the stator of the common, 3600 RPM two pole generator are? You KNOW they will be fighting each other when connected in parallel.... but you need to understand that even when that happens, it most likely falls within acceptable limits (which are probably pretty generous) of what the tolerance is per winding output.
> 
> If you tried to convince me the two windings would be so far out of whack that you would take total a total max output of (example) an 8500 watt peak, 10HP Brigss and knock that sucker down to a peak of 5000 watts max (due to internal losses), I would listen to what you have to say.
> 
> But what *IF* you only lost 100 watts? Maybe a 250 watt loss? How about 500? Well, that would be acceptable in this case.
> 
> If I needed to run my well, but I could only afford a $599 Home Depot special that puts out a continuous 5500 watts (ideal conditions, LOL) at 240 (half of which is 2750) on one 120 volt outlet, then darn tootin', I'll take a loss if I can re-configure the windings and get say... 4800-5000 watts continuous at 120. that is very acceptable.
> 
> 3600 RPM two pole units are not that perfect to begin with, how much more "un perfect" would we make one if we paralleled the stator windings, seriously? Onan has been doing this for 50 years, are they really built that much better (well, those of us who own them would agree, but that's another story  )


My statements haven't had a single thing to do with losses in power output. It has nothing to do with the "quality" of electricity produced. It has nothing to do with efficiency.

As far as your question about 2 3600 RPM generators in parallel... The statement that you "KNOW" they will be fighting is incorrect. Only if the setting are incorrect will they oscillate and even then it's only in respect to frequency. As I stated earlier, the droop circuit prevents any voltage regulator issues.

Here's a load sharing graph. The horizontal line QG1 to QG2 or QG'1 to QG'2 is the actual power. They are exactly equal but shifted due to the regulator settings. The distance it covers on the left is the amount of load carried by generator 1, the distance on the right is the amount carried by generator 2

The middle shows the "no load" voltage regulator settings of both generators










QG shows that generator 1 is carrying just about all the load and generator 2 is carrying almost nothing. QG' shows that by raising the setting of gen 2 closer to gen 1 it picks up more load. If the gen 2 setting was lowered from the first example it would actually flip along it's horizontal axis (both sides rising from left to right) causing gen 1 to carry all the load but put additional power into gen 2 which has started motoring.

Without a droop circuit the lines are flat. There is no decrease in voltage as load rises. Unless the voltages are PERFECTLY matched, you have circulating currents which will produce some amount of increased current, heating and physical torque. How much depends on the amount of voltage difference.

Home generator windings don't have droop circuits. There is a risk of damage to the generator in the modified configuration.

*Damage*, not efficiency, power or the cleanliness of the electricity is my concern.

_I'd still like to know why manufacturers don't include this functionality if it's so simple._ Perhaps they realize the potential for damage.


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## Viking

How in the world can a simple post that LincTex put together to help others get so complicated? All that he has done is show what can be done to give more amps for starting motors that have high current needs for getting up to speed, (locked rotor amperage ratings). So here's my two cents, the cheap Chinese made Lifan 8000iE generator we bought has one thing that is different than LincTex's generator, it has a Voltage Selector which the wiring diagram shows a Voltage Selector list of which switches need to be on or off to run parallel windings for 120VAC or 120/240 VAC for split phase. In the generator LincTex has I doubt the manufacturer thought a selector switch was a necessity. The way he wired his generator is no different than if I changed the switches on mine for doubling the 120 volt amperage capability. As to LincTex's mention of wattage loss, I doubt it would amount to anything close to even the 100 watts he mentioned.


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## LincTex

labotomi said:


> I'd still like to know why manufacturers don't include this functionality if it's so simple. Perhaps they realize the potential for damage.


I think they do.... but I think it actually has more to do with amperage ratings of the receptacle, since some manufacturers DO INDEED offer this option (Onan, also Kohler very likely). 4800 watts equals 40 amps at 120 volts, and a normal 20 amp outlet was not designed to handle that load for extended periods. For a short time - yes, no problem at all - but it still places them in a position of liability. They could add a 30 amp RV plug (which would be a popular feature) but it also adds cost.

They know full well that inrush current to get larger motors started exceeds 20 amps, but the breakers needed to delay tripping until after the motor is started add (again) to production cost. Cheaper breakers means more profit. People also may be swayed to buy a larger unit than they really need, and that is profitable too.

I was so amazed 8-9 years ago when I plugged a "normal size" 120 volt household air compressor (2-3 HP?) into a "pretty decent" sized generator (8hp?) and had the breaker trip immediately. In fact, the engine sounded as though it barely attempted to pick up the load before the breaker tripped. I was pretty upset, it should have easily handled the load (IMHO)! That is when I learned that only half of the stator output was available. Even if the breaker hadn't tripped, the entire load would have been carried by only one set of stator windings, and I know that it isn't a good idea to have a lot of imbalance between windings within the stator.

Also, I respectfully ask that you refrain entirely from bringing into this discussion the subject of paralleling two entirely separate generators. That is not what I have ever intended this thread to evolve/devolve into, as it is an exercise/evolution that very, very few people would ever attempt to undertake, including myself (not that I wouldn't try for curiosity's sake, but I see no immediately practical reason to try).

I am interested in hearing how/or why you believe that paralleling synchronous windings within the same stator would be dangerous or cause damage (they "look" pretty damn tightly wound and consistently wound to me), but if you go down that path your info submitted must be specific to that situation. I have very little interest in learning about synchronizing separate generators at this time, and I would like to cease discussing them.


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## labotomi

LincTex said:


> Also, I respectfully ask that you refrain entirely from bringing into this discussion the subject of paralleling two entirely separate generators. That is not what I have ever intended this thread to evolve/devolve into, as it is an exercise/evolution that very, very few people would ever attempt to undertake, including myself (not that I wouldn't try for curiosity's sake, but I see no immediately practical reason to try).


The concept is identical. I'm sorry if you don't recognize that. Since there is no information or graphs on paralleling windings available. I was showing what the effects would be using the generator examples. Then as some (including you) started commenting on generator paralleling, I responded to their comments. Just because 90% of people don't know what factors affect paralleling of windings doesn't mean they wont be affected.

It wasn't about connecting two separate portable generators together. I'm not sure you understand the concepts and how they relate. If you do then I don't see why you fail to see the correlation. My first post was fairly simple. I never intended to get in depth on any part of this but you dismissed it as not a concern then later discussed it in a way that showed a complete misunderstanding of what I had stated and the concerns.



LincTex said:


> I am interested in hearing how/or why you believe that paralleling synchronous windings within the same stator would be dangerous or cause damage (they "look" pretty damn tightly wound and consistently wound to me), but if you go down that path your info submitted must be specific to that situation. I have very little interest in learning about synchronizing separate generators at this time, and I would like to cease discussing them.


Have I not explained exactly that... starting with my first post in this thread?

As far as looking good, could you see a shorted winding? It would electrically eliminate one wrap from the winding coil and that alone affects the voltage output. It wouldn't cause problems and nobody would notice with the original wiring configuration. It would cause problems in the new wiring configuration. Shorted windings are not that uncommon in operating generators. When many become shorted the problems are noticed.

You'll probably admonish me for using a motor example instead of generator specific but I don't test generators, I test motors. The concept is identical.

I use some very comprehensive test equipment on critical motors when they come to our facility. In addition to the basics (coil resistance, resistance to ground etc.) it tests for lamination defects and shorts, shorted windings, inductance, polarization and magnetization current. All of which affect how the motor operates.

Two brand new identical motors will not have the same values. There are too many variables in construction. Even the best companies can't produce identical motors. The same can be said for generators as the manufacturing process if virtually identical.

I don't plan on responding to this thread again. At this point I don't care if anyone understands or agrees what I've written about the potential for damage. If some of the people who do this end up with damaged generators it's not going to affect any of mine.


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## LincTex

Well, for someone with only a high school education, I consider myself to be far from an idiot (I am not saying you are calling me one, BTW) but instead of telling the readers of this thread "what the time was" I feel the information you were presenting fell more along the lines of "how the clock works" (per se). ... or some other more applicable metaphor....

The issue I was trying to put emphasis on was parallel windings in the same stator were subject to an equal amount of lines of flux from an energized rotor. I still fail to see how two conductors lying beside each other, and of equal resistance (assuming such for now) would have a great enough detrimental effect to prevent this from being a successful modification. I understand the possibility of why it would occur, but I feel the plausibility or likelihood of damage occurring is far enough remote that it should not only raise any concern, but isn't worth mentioning. By the same token, you have yet to address how the Onan corporation has successfully (for decades) sold generator in which the windings in the stator could be connected in either "W" connection with two legs with 240 volts between them and 120 to center, or connected in parallel so that the voltage remains at 120 but the capacity for amperage doubles (theoretically). Your unwillingness to discuss that aspect makes me believe the information you present on the possibilities of damage or danger do not hold merit. Surely, if risks exist, why then does one of the largest powerplant makers in the USA offer the ability to connect windings in such a way?

The generator end I was discussing having examined while apart was not at fault; disassembly occurred in order to change and engine out that had run low on oil and had seized. It was a gift, and since the crank was salvageable I made one good engine from two, and put the generator back into service. There were no burned windings (evidence of a short)

The reason I got so annoyed with your bringing two separate generators into the discussion is that by doing that, you throw in far too many variables into the mix. In synchronous parallel windings within the same stator, the number of variables is reduced immensely. The windings are made from wire of most likely the same batch/lot of manufacture, the windings experience equal amount of flux from the rotor (within tolerance), etc. etc. So where is the concern here?

I quote you: "Even with the stator windings physically side by side there will be slight difference in the resistance, air gap, iron core and laminations." Yes, there are - - - but these variances are all *NEGLIGIBLE*. They have to be, or the generator would NOT FUNCTION in the intended market for which it is sold to. Nobody builds them to that level of precision, and still have a marketable (due to price point) product.

it sounds as though you are saying any imbalance between the windings (and between outlets) should be cause for concern? How? You have supplied an amazing amount of engineering level information, but I do not feel you have supplied a detailed description that warrants this warning: "Home generator windings don't have droop circuits. There is a risk of damage to the generator in the modified configuration. Damage, not efficiency, power or the cleanliness of the electricity is my concern."

To what level (or rather, parameters) must the windings be exposed to, to reach a level of concern? And though it sounds great in theory, what must actually occur to have said damage actually happen?

Can you describe a scenario that supports that argument - purely from a "consumer-grade-level genset" aspect? Why doesn't "voltage droop" also occur when unequal loads are placed up the separate windings due to differences of load between separately wired outlets (due to lack of a voltage droop circuit)?

Certainly, I once again reiterate the appreciation of knowledge you bring to this discussion. I think you are looking at this from a state-of-the-art power station perspective, not a crude, gasoline fueled, mass-produced consumer product perspective.

If I seem heated, it is because I am frustrated by the appearance of you not fully explaining why you believe there is cause for concern to paralleling synchronous windings, especially when there ARE manufacturers that allow this same practice to be performed with their units.

This whole conversation reminds me a little about the old Chinese Proverb: "Those who say it cannot be done should not interrupt the person doing it."

Why does Onan allow it without any danger to their unit, or to the user?



labotomi said:


> Two brand new identical motors will not have the same values. There are too many variables in construction. The same can be said for generators as the manufacturing process if virtually identical.


*Sigh*..... I am not arguing that with you. 
I wish you would quit on the whole "two separate entities" thing. 
Let's focus strictly on ONE stator, wound from copper wire most likely from ONE lot, with ONE energized rotor, emanating ONE measured Gauss of flux, which is spinning at ONE set RPM, with ONE set of laminations, inside ONE case. OK?!?!?!? Please, no more variables. Just focus on what is happening inside that ONE case only. Only variable allowed: two windings, side by side....nothing else.


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## Viking

LincTex said:


> I think they do.... but I think it actually has more to do with amperage ratings of the receptacle, since some manufacturers DO INDEED offer this option (Onan, also Kohler very likely). 4800 watts equals 40 amps at 120 volts, and a normal 20 amp outlet was not designed to handle that load for extended periods. For a short time - yes, no problem at all - but it still places them in a position of liability. They could add a 30 amp RV plug (which would be a popular feature) but it also adds cost.
> 
> They know full well that inrush current to get larger motors started exceeds 20 amps, but the breakers needed to delay tripping until after the motor is started add (again) to production cost. Cheaper breakers means more profit. People also may be swayed to buy a larger unit than they really need, and that is profitable too.
> 
> I was so amazed 8-9 years ago when I plugged a "normal size" 120 volt household air compressor (2-3 HP?) into a "pretty decent" sized generator (8hp?) and had the breaker trip immediately. In fact, the engine sounded as though it barely attempted to pick up the load before the breaker tripped. I was pretty upset, it should have easily handled the load (IMHO)! That is when I learned that only half of the stator output was available. Even if the breaker hadn't tripped, the entire load would have been carried by only one set of stator windings, and I know that it isn't a good idea to have a lot of imbalance between windings within the stator.


This is exactly what happened to me with the 8000 watt Lifan this past winter, the engine didn't skip a beat as the breakers popped with ease. The power had been out for 32 hours due to heavy snow dropping a tree on the power lines when I finally dragged the generator down from the woodshed (the very first time I've used it) and tried running a couple of refrigerators off of either of the 120 outlets on the generator, I ended up wiring a heavy extention cord to the 120 volt 30 amp RV type outlet that thankfully had been installed on this generator. I may end up installing different breakers for the two duplex 120 outlets as I'd be surprised if they wouldn't pop by trying to run my Black and Decker or miter saw as they draw a lot of starting current.


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## Viking

LincTex said:


> Well, for someone with only a high school education, I consider myself to be far from an idiot.
> 
> This whole conversation reminds me a little about the old Chinese Proverb: "Those who say it cannot be done should not interrupt the person doing it."
> 
> Why does Onan allow it without any danger to their unit, or to the user.


 Or my Chinese made Lifan? The above statements resemble my background as well and the Chinese Proverb is like my saying which I expropriated from a baseball hat a few decades ago, "I've done so much with so little for so long I can do almost anything with nothing." And so it is that people like LincTex, others and myself can do things which other "learned" people think cannot be done, we are part of a group of people that can truly make lemonaid out of lemons. When others have all the appropriate tools to do something we make due with Visegrips, Channel lock pliers and "C" clamps, we sometimes use our pickup bumpers for work benches when we don't have something solid, like bending rebar when we don't have a rebar bending tool. In the end it's all about common (or in these days uncommon) sense. So please don't interrupt those of use doing things that work by saying it can't be done because we'll just end up showing that it can be done.:soapbox1:


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## LincTex

As always, VERIFY your circuits before attempting this; it is for reference only.


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## labotomi

Viking said:


> Or my Chinese made Lifan?
> <<<snip>>>
> And so it is that people like LincTex, others and myself can do things which other "learned" people think cannot be done


Nobody is saying it can't be done, but if that's what you need to make you feel good about yourself or somehow better than the "learned" people. then by all means use it as a chip on your shoulder. Go ahead and look down on "us" who are attempting to save you from difficulty. 
I'm not saying this to make you feel inferior and despite your attempts to make me feel so... I do not feel inferior because of my education, training and experience (nor should I)

I'm not sure how to highlight the potential for damage in terms that are easy for everyone to understand and I'm not going to rephrase or try another method. Where I'm trying to help... you are looking at it as a you vs me argument to be won or lost.

My entire point about this is that the possibility to damage your generator exists if you do this modification. That danger isn't there without the modification.

Some units such as the Onan or Lifan may have been designed around this method of operation and as such have circuitry that compensates for any inconsistencies. It's obviously possible to operate with generators in parallel since it's done everyday, but that doesn't mean every generator is capable of operating in parallel with every other generator.


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## LincTex

labotomi said:


> It's obviously possible to operate with generators in parallel since it's done everyday, but that doesn't mean every generator is capable of operating in parallel with every other generator.


Nobody is suggesting that two separate units can be tried to make run as synch'd units.


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## elder

LincTex is correct on this. His schematic shows a single phase generator with identical windings, if not they wouldn't add for the 240v output. The concept is similar to a transformer that can be wired for 120v or 240v, the windings being on the same core.


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## Viking

labotomi said:


> Some units such as the Onan or Lifan may have been designed around this method of operation and as such have circuitry that compensates for any inconsistencies. It's obviously possible to operate with generators in parallel since it's done everyday, but that doesn't mean every generator is capable of operating in parallel with every other generator.


All that LincTex and I have talked about has been about ONE generator and hooking up same phase windings to double the output of amperage of that generator to be able to get a motor up and running that one winding would not do. I'd really be surprised if a majority of home generators were not set up, with switches or connection terminals, to change them from 120/240 split phase to match phase parallel 120. My friend who works on motors, some so large only one can be carried on a large flatbed trailer and generators, some of which are run by 16 cylinder engines, also rewinds motors and generators. If he told me there is no problem paralleling windings, phased properly, then I see no problem. I'd really be surprised if in rewinding generators that he ends up using almost the same footage of wire per winding, if nothing else simply because he is a perfectionist to the most finite degree. So if this man tells me that the windings of generators can be paralleled I believe him. As to paralleling generators, that's for the power companies to do and certainly is not my concern. LincTex mentioned that some Honda generators could be paralleled and it seems to me that I read something about that but those generators likely are inverter types that need a connection between each set to bring them into the same phase just like my home solar back up pure sine wave inverter can be stacked up to four units. The only thing I had to do is to get a router unit that additional inverter need to plug into. Now, as to putting other people down, I'm certainly not trying to do that and can only figure that cabin fever has set in and some that are locked in due to all the bad weather are going a bit stir crazy. Aren't we all here to give a bit of help to figure out some short cuts to save fellow preppers from spending too much hard earned cash when a simple fix will do the trick? As far as I'm concerned LincTex certainly fulfilled that service because a lot of us that have small gen sets seldom use the 240 volt output but need extra motor start capabilities that are available by paralleling windings.


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## labotomi

elder said:


> LincTex is correct on this. His schematic shows a single phase generator with identical windings, if not they wouldn't add for the 240v output. The concept is similar to a transformer that can be wired for 120v or 240v, the windings being on the same core.


It is NOT the same concept as a multi tap transformer. It's very easy to see the difference if you look at the wiring schematics of each.


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## labotomi

Viking said:


> All that LincTex and I have talked about has been about ONE generator and hooking up same phase windings to double the output of amperage of that generator to be able to get a motor up and running that one winding would not do.


Yes, you talk about one generator but internally that one generator has two stator windings. Those two stator windings have voltage induced into them independently of the other. They share the prime mover and rotor field but in essence they act as separate generators.



Viking said:


> My friend who works on motors, some so large only one can be carried on a large flatbed trailer and generators, some of which are run by 16 cylinder engines


Am I to state the size of motor and generators I've dealt with? 1750Hp 4160V AC, and 2250Hp DC variable voltage and speed are the two types I deal with the most right now. Previously I was involved with the regulator design on 3600KW turbine generators.



Viking said:


> As to paralleling generators, that's for the power companies to do and certainly is not my concern.


You're unable to see, even with the schematics, that it's exactly what you're doing when connecting the windings in this fashion?



Viking said:


> Aren't we all here to give a bit of help to figure out some short cuts to save fellow preppers from spending too much hard earned cash when a simple fix will do the trick?


And that's different than what I'm doing? Let me quote myself.



labotomi said:


> I'm not sure how to highlight the potential for damage in terms that are easy for everyone to understand and I'm not going to rephrase or try another method. Where I'm trying to help... you are looking at it as a you vs me argument to be won or lost.
> 
> My entire point about this is that the possibility to damage your generator exists if you do this modification. That danger isn't there without the modification.
> 
> Some units such as the Onan or Lifan may have been designed around this method of operation and as such have circuitry that compensates for any inconsistencies. It's obviously possible to operate with generators in parallel since it's done everyday, but that doesn't mean every generator is capable of operating in parallel with every other generator.


When this topic was being discussed, I did some of the calculations to see how much difference would be needed for definite problems to develop as LincTex had asked. I came up with just under a 5% difference in the windings/air gap/field/regulator. Granted... there had to be a lot of assumptions made because the exact specifications and regulator mode are unknown and possible different on the various models even from the same manufacturer. Is that 5% outside what you would be concerned about? I'd bet that the majority of generators would operate within that margin of error. I'd also bet that there would be some that would end up with damaged windings because they were outside that margin of safety.

I care not whether any particular person operates their generator one way or another. As I stated before, I'm trying to put out information even if it's not what people want to hear.


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## elder

labotomi said:


> It is NOT the same concept as a multi tap transformer. It's very easy to see the difference if you look at the wiring schematics of each.


I didn't say multi-tap transformer but transformers or motors with separate windings can be wired for 120v or 240v operation. Multi-taps are limited to voltage selection only, i.e. a center tapped generator winding could not be paralleled.

In a single phase generator the windings are on the same magnetic core with mutual inductance but no phase difference other than polarity of windings. Windings may appear separated on a schematic but in the machine they are wound together.


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## labotomi

elder said:


> In a single phase generator the windings are on the same magnetic core with mutual inductance but no phase difference other than polarity of windings. Windings may appear separated on a schematic but in the machine they are wound together.


I've addressed all of this in previous posts.


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## LincTex

labotomi said:


> I've addressed all of this in previous posts.


Are you referring to the possibility of the windings being placed in stator slots that are not wound "two-in-hand"? (bifilar windings)

I would have to disassemble the generator to verify this. Maybe Onan does indeed have bifilar windings so that the two circuits are wound at the same exact time and the wires lie next to each other and share the same slots in the stator.

Are you trying to infer that the windings may share a common stator, *but not the same stator slots?* That would make them slightly out of phase... and if that were the case then the gen manufacturer would never be able to offer a 240 volt receptacle on their machine. Correct?


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## LincTex

labotomi said:


> Granted... there had to be a lot of assumptions made because the exact specifications and regulator mode are unknown and possible different on the various models even from the same manufacturer. ... I'd bet that the majority of generators would operate within that margin of error. I'd also bet that there would be some that would end up with damaged windings because they were outside that margin of safety.


The voltage regulator of an early 70's Onan is simple device and has no compensation circuit for errors. They are very simple and somewhat crude from an electronics engineering standpoint.


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## LincTex

labotomi said:


> I came up with just under a 5% difference in the windings/air gap/field/regulator. Granted... there had to be a lot of assumptions made


You would have to have substantial differences in tolerance occurring and very sloppy manufacturing practices to get enough variation to cause any problems, or the 240 volt receptacle wouldn't function (stator series wired) very well either.


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## labotomi

LincTex said:


> You would have to have substantial differences in tolerance occurring and very sloppy manufacturing practices to get enough variation to cause any problems, or the 240 volt receptacle wouldn't function (stator series wired) very well either.


Again, I would disagree. Maybe if we were limiting this to brand new off the shelf generators. The amount of generators that end up with shorted windings after moderate use would probably surprise you. I'm going to say 30% but I'm pretty sure the number was a bit higher. These generators would still be operational but with lowered ratings. I haven't seen any information on portable residential generators but I would suspect that they would have a higher instance of this due to poor storage and operating conditions along with higher stresses due to vibration and lack of cooling. A new generator would be much less likely to have these problems until they were put through their paces or subjected to harsh environments.

a 5% drop in a 120V circuit is only 6 volts. The field is shared by both windings and the output of the field would be determined by where the voltage is measured. The diagram you provided doesn't show where that value is obtained.

If it were taken from the lower voltage winding, the field current would increase to bring it back to 120V and thus the other winding would go up above 120V by the same value. If it were taken by the non damaged winding the voltage would remain low in the damaged winding. If it were an average of the two, it would raise the voltage so that one is above and one is below 120V by the same magnitude. In all three cases the voltage would remain different.

In that condition the higher voltage winding *will* assume a greater portion of the load. It could potentially (depending on how the field circuit is regulated) assume all the load and only when the good winding was overloaded and it's voltage dropped to that of the damaged winding's level would the damaged winding start assuming some of the additional loading.


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## elder

If there is a minor voltage difference there will be circulating current and a bit more copper loss. If a floating neutral the neutral will seek a new level. 

Phasing not so much a problem, I know we are talking single phase but two phase generators actually can have another voltage by summing the 90 degree outputs to get a voltage that is 1.414x the in-phase voltage.


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## labotomi

elder said:


> Phasing not so much a problem, I know we are talking single phase but two phase generators actually can have another voltage by summing the 90 degree outputs to get a voltage that is 1.414x the in-phase voltage.


Where do you encounter a two phase generator?


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## elder

labotomi said:


> Where do you encounter a two phase generator?


Truth is I don't think have never encountered one except as a textbook concept, they were used in the early days of AC. I don't recall if we had one in the EE lab or not. I only mentioned them as two phase power does (or did) exist and the phases could be summed, as they are in three phase power.


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