# Can a DC welding generator be used as a motor ?



## Rusty (Mar 31, 2013)

G,Day Blokes,
I am thinking of building an electric vehicle and was wondering about a source of electric motor for it. All the DIY sites I have read suggest electric forklift engines or specially built EV motors by the various manufacturers, only problem with this is I don't want to spend the cash on a professional motor unless I am sure I can build the vehicle to a decent standard and out here (in Western Australia) there are almost no old electric forklifts to rat parts off so I can't get one from that source. I do however have access to several old DC welding generators capable of generating 200 plus amps of current at somewhere around 36 to 45 volts (or so I am told), they would I assume be shunt wound and physically not a lot different to some of the engines used by a lot of conversions but are designed as "generators" not "motors". My understanding is that motors and generators have very similar design characteristics and that generators can be made to motor if wired up correctly BUT can a DC generator like that be made to perform even marginally acceptably or would it either not produce "useable" power or just flatten a battery bank in very short order.

Strange question I know but does anyone have a view ?
Graham


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## major (Apr 4, 2008)

Rusty said:


> G,Day Blokes,
> I am thinking of building an electric vehicle and was wondering about a source of electric motor for it. All the DIY sites I have read suggest electric forklift engines or specially built EV motors by the various manufacturers, only problem with this is I don't want to spend the cash on a professional motor unless I am sure I can build the vehicle to a decent standard and out here (in Western Australia) there are almost no old electric forklifts to rat parts off so I can't get one from that source. I do however have access to several old DC welding generators capable of generating 200 plus amps of current at somewhere around 36 to 45 volts (or so I am told), they would I assume be shunt wound and physically not a lot different to some of the engines used by a lot of conversions but are designed as "generators" not "motors". My understanding is that motors and generators have very similar design characteristics and that generators can be made to motor if wired up correctly BUT can a DC generator like that be made to perform even marginally acceptably or would it either not produce "useable" power or just flatten a battery bank in very short order.
> 
> Strange question I know but does anyone have a view ?
> Graham


Hi Graham,

Any electric motor can be operated as a generator or vice versa if properly excited. Excited meaning the field in this case. As you note, the welder is likely a shunt wound machine whereas most forklift motors used in EVs are series wound. So, not insurmountable, but it would be a challenge to find or build a proper controller. 

Other than that, the generator may not have been designed with efficiency of great concern, nor its weight, both of which are important factors in the EV. You could certainly give it a go. If it was all I had to work with, I'd do it 

major


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## Rusty (Mar 31, 2013)

Thanks Major !
Even by saying what you have I feel I wasn't a complete nut case for considering such a thing, "thanks for that" !

Why would the controller be more difficult than for a series wound machine ? The amount of current would be the same wouldn't it ? or would it have to have variable current independently fed to both the armature and the fields.


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## major (Apr 4, 2008)

Rusty said:


> Thanks Major !
> Even by saying what you have I feel I wasn't a complete nut case for considering such a thing, "thanks for that" !
> 
> Why would the controller be more difficult than for a series wound machine ? The amount of current would be the same wouldn't it ? or would it have to have variable current independently fed to both the armature and the fields.


Yeah, by definition, the series motor has the field in the armature circuit, so the controller output current goes thru both and you automatically get a strong (high current) field when you have high armature current. With the shunt field, the field is across the source and independent of the armature current. Therefore shunt motors are seldom used for EV propulsion because at high armature loading (accelerations) the field is too weak resulting in poor torque and/or commutation arcing.

The use of properly wound "shunt type" fields called separately excited or SepEx can be used to mitigate this trouble but require different wire in the coils and a SepEx controller. It is possible your generator has some compensating windings which might be usable as series field but that might require some internal mods.

All most all EV motor controllers are of the type intended for use with series motors. They may be able to control the voltage and current to the armature of the shunt motor and have your shunt field connected directly to the battery. If done this way, you would need to keep overloading to a minimum, meaning a low to moderate armature current limit. Acceptable vehicle acceleration then may be achievable with the use of a transmission.


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## Rusty (Mar 31, 2013)

"Ah Ha", the penny may not have dropped but its wobbling a bit !

I doubt there is any "compensating windings" in any of the generators, I think they are pretty basic in their design. I don't have them with me at the moment, they are up on the farm and I am down on the coast but I will have a look next time I am up there, I recon I should be able to pick things like that by the wiring.

Do you know of any link that would discuss this type of scenario ? I have looked around and the DIY forum seems the best I have found so far.

Thanks Major,
Graham


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## PStechPaul (May 1, 2012)

I found a schematic for a welder/generator, and it appears that it is an AC generator with a separate stator winding and rectifiers for welding. So it may not be usable as a DC motor unless you use an inverter. It will also be a synchronous machine which may not work well as a traction motor.

http://www.docstoc.com/docs/51279153/Hobart-Champion-16-Welder-Generator

You might look for a DC motor/generator set like this:
http://www.ebay.com/itm/20KW-DC-GENERATOR-SET-125-VOLTS-DC-/130679337328

or this:
http://www.ebay.com/itm/40-HP-RELIANCE-ELECTRIC-AC-DC-Motor-Generator-Set-/330369895336

And here's a 5 kW DC generator that will probably work as a motor:
http://www.ebay.com/itm/GE-KINAMATIC-DC-GENERATOR-45KW-/220723351298


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## Duncan (Dec 8, 2008)

Hi Rusty

Have a look for electric forklifts, - you will find them at abattoirs, and food handling in general,
Anywhere where the fumes could cause problems - is Western Australia mostly agricultural?
Mines could also use electrical handling machines

I have just been at Waitane Meats (sheep processing) - I saw two electric forklifts and I only saw 10% of the site


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## Rusty (Mar 31, 2013)

Thanks Paul but the generators I have are just basic generators with normal DC commutators and large brushes and fitted with basic field coils, no AC involved and no stator winding only the DC armature. They were originally car engine powered or mounted onto tractors, one is set up for tractor power take off operation. Three have no provision for tapping the electrical circuit as a power source and one has a power outlet to operate tools ect on 32 volt DC. 32 volt used to be the standard power generator voltage in our area before the mains power was put through.
It sounds like the welder "may" be feasible so I think I will look into it a bit more, but its not going to stop me looking for a forklift engine, just I will have to be very lucky to find one.

Thanks guys,
Graham


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## Rusty (Mar 31, 2013)

Duncan said:


> Hi Rusty
> 
> Have a look for electric forklifts, - you will find them at abattoirs, and food handling in general,
> Anywhere where the fumes could cause problems - is Western Australia mostly agricultural?
> ...


 
Thanks Duncan,
I hadn't considered looking there ! I think I have only ever seen one electric lift and that was at a carpet warehouse. I will definitely keep on looking hopefully something may turn up, will make it a lot easier if it does.
Graham


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## electro wrks (Mar 5, 2012)

PStechPaul said:


> I found a schematic for a welder/generator, and it appears that it is an AC generator with a separate stator winding and rectifiers for welding. So it may not be usable as a DC motor unless you use an inverter. It will also be a synchronous machine which may not work well as a traction motor.



Rusty is referring to the large, super reliable, old school DC welding machines still made and preferred by the pipeline and offshore oil and gas people. They have few or no electronics to go bad and put out a very smooth (low ripple) DC current for consistently good welds.

Most still have a small field excitation generator sticking out one end. For use in a EV, this could be cut off and electronic field control substituted. AIR most units have the armature bolted directly to the ICE flywheel. So, a bearing, shaft, and end housing arraignment would have to be fabricated. And, they're very heavy.

Like Major says, If you have access to one and the inclination to tinker, try one out! The few that have passed my way were still attached to perfectly good welding units. Although, I wonder if that one down the street in the woods behind a neighbor's house is still there. I'd need a chain saw to free it up, as it had a tree growing up through the works!


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## Rusty (Mar 31, 2013)

electro wrks said:


> Rusty is referring to the large, super reliable, old school DC welding machines still made and preferred by the pipeline and offshore oil and gas people. They have few or no electronics to go bad and put out a very smooth (low ripple) DC current for consistently good welds.
> 
> Most still have a small field excitation generator sticking out one end. For use in a EV, this could be cut off and electronic field control substituted. AIR most units have the armature bolted directly to the ICE flywheel. So, a bearing, shaft, and end housing arraignment would have to be fabricated. And, they're very heavy.
> 
> Like Major says, If you have access to one and the inclination to tinker, try one out! The few that have passed my way were still attached to perfectly good welding units. Although, I wonder if that one down the street in the woods behind a neighbor's house is still there. I'd need a chain saw to free it up, as it had a tree growing up through the works!


Yes that's exactly what I have got, solid and simple, no electronics anywhere, I don't think there is anything separate from the machine as an excitation generator on them, but I will have a look when I get the chance (be a week before I am up at the farm) They are all self contained with bearings at both ends and a 15/16 shaft sticking out one end for operation by a belts. Two units are made by EMF and the other two are Lincolns.


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## electro wrks (Mar 5, 2012)

Rusty said:


> Yes that's exactly what I have got, solid and simple, no electronics anywhere, I don't think there is anything separate from the machine as an excitation generator on them, but I will have a look when I get the chance (be a week before I am up at the farm) They are all self contained with bearings at both ends and a 15/16 shaft sticking out one end for operation by a belts. Two units are made by EMF and the other two are Lincolns.



So much the better. I'm not familiar with belt drive units. Post pics and nameplate info, if you can.


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## thewierdquestionguy (11 mo ago)

major said:


> Hi Graham,
> 
> Any electric motor can be operated as a generator or vice versa if properly excited. Excited meaning the field in this case. As you note, the welder is likely a shunt wound machine whereas most forklift motors used in EVs are series wound. So, not insurmountable, but it would be a challenge to find or build a proper controller.
> 
> ...


i have a similar question but a different application of the welding machine. Could employing a DC welding machine like a Miller Bobcat 250 be suitable as an alternative power source? Yes it would still require Gas/Diesel fuel and on a skid it weighs over 500 pounds without fuel, then exaust, etc. Still, is it a viable alternative to using batteries, which are very heavy and expensive. what is the possible DC motor that could operate with that kind of power source? 

FYI: Im considering a home made 1/4 mile electric monster. im not a purist, so im trying to think of ways to deliver power and maybe see the look on track purist who just got smoked, literally, by a hybrid. LOL. All joking aside, I'm serious.


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## remy_martian (Feb 4, 2019)

Sell the welding gensets, buy a Nissan Leaf 200hp motor for the money, have money left over for a case of beer.


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## piotrsko (Dec 9, 2007)

Yes it may output massive watts, but you want higher voltage over current instead of current at a low voltage. Welders generally don't go high voltages (>100v) , motors prefer high voltage, power wiring is ditto.

Was my experiences In bracket racing that showing your oponent your tail lights during the first 1/8 caused them to generally blow their bracket trying to beat you.


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