# Alternator to motor conversion



## kamaaina (Jan 12, 2022)

Bump... I would like to do the same thing.
is it as simple as finding an AC speed controller and connecting the right wires or does the unit itself need to be wired for DC?


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## brian_ (Feb 7, 2017)

kamaaina said:


> is it as simple as finding an AC speed controller and connecting the right wires or does the unit itself need to be wired for DC?


There's not way to "wire it for DC", because it doesn't have a commutator; you would need a suitable controller-inverter.


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## kamaaina (Jan 12, 2022)

brian_ said:


> There's not way to "wire it for DC", because it doesn't have a commutator; you would need a suitable controller-inverter.


Thanks for chiming in.. maybe I was confusing 3 phase to 2 phase ac/dc ? IDK what i'm talking about.. I play with things until they break or catch fire and I get hurt. What I'm trying to ask you is if there is any modification necessary to turn this type of generator into an electric motor? I know some car alternators have a 12v line running to them to create the electric field for charging and the - commutator - would be the rectifier switching the AC out to DC out... is it as simple as running it backwards and pushing energy into it with some sorta suitable controller? 

It would appear to me (i dont know shit btw) that the rotor would either need to be modified or provisions made to excite that field. 

seriously thanks; 

it would be much appreciated if you could just tell me how this would be feasible or if it would even be worth the trouble. what kinda values could this theoretically produce? does the power rating/consumption stay the same like 6500watts for example. honestly I don't expect you to reply.. i know i sound like a child


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## remy_martian (Feb 4, 2019)

Why do you want to do this and what is the target installation?


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## TeZla (Feb 18, 2021)

There's a start.

In a simple explanation, an alternator can be turned into a 3 phase AC motor. You need a suitable controller to do that. you can get them off ebay for a good price, Just look for something suited to an ebike or similar sized motor. As it stands though, they don't make very good motors, as there is no way for the controller to 'know' where the rotor is in its phase cycle. you can fix that by installing 3 hall sensors into the stator, to detect the rotor.
That is a good little project that'll teach you about 3 phase motor basics, but there is still a bit of a learning curve in figuring out where to put the hall sensors, how to wire them, what order they go in etc.
You also need to feed power to the rotor, via the slip rings and a modified/gutted regulator. Its not as simple as just feeding it 12v either, while that will work, there is a lot of tuning to get the voltage just right, which also varies depending on the rotor speed.

If your not afraid of a bit of tinkering, circuitry and theory, then jump right into it. If your expecting it to be a really simple hand held excersize, probably stop now and just buy a proper designed motor.


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## brian_ (Feb 7, 2017)

kamaaina said:


> ... maybe I was confusing 3 phase to 2 phase ac/dc ? IDK what i'm talking about.. I play with things until they break or catch fire and I get hurt.


2-phase power is very rarely used; when people say "2-phase" they usually mean split single-phase (such as the 240/120 volt service found in North American homes). But whether the alternator is for single-phase or three-phase power doesn't change the situation fundamentally.



kamaaina said:


> What I'm trying to ask you is if there is any modification necessary to turn this type of generator into an electric motor?


What's "this type"? In the original post of this thread an alternator from a generator set was shown which is significantly different in details from the alternators typically used in vehicles to supply 12-volt power. TeZla's post is about automotive alternators, not that one from a genset.



kamaaina said:


> I know some car alternators have a 12v line running to them to create the electric field for charging and the - commutator - would be the rectifier switching the AC out to DC out... is it as simple as running it backwards and pushing energy into it with some sorta suitable controller?
> 
> It would appear to me (i dont know shit btw) that the rotor would either need to be modified or provisions made to excite that field.


Those are two good observations: the wound rotor needs excitation (whether the machine is operating as a generator (alternator) or as a motor) and something needs to convert between AC and DC (which is done by a commutator in a DC motor, but there's no commutator in an alternator).

In the alternator of the generator set shown, the AC is output is used directly so there is nothing converting it, and the machine could probably be driven without modification by a suitable inverter; there is presumably a rectifier internally to produce the DC power needed for the rotor.

In automotive alternators, AC power output is not wanted so they include a rectifier, which needs to be removed (as TeZla mentioned) so the individual phase windings of the stator (normally three phases) can be driven by an inverter. The DC power supply to the rotor (through slip rings) could be left simply connected to 12 volts or varied by another controller for efficiency.

I don't see any reason to modify the rotor, in any case.



kamaaina said:


> it would be much appreciated if you could just tell me how this would be feasible or if it would even be worth the trouble. what kinda values could this theoretically produce? does the power rating/consumption stay the same like 6500watts for example.


The power capability would be roughly similar in motor mode to what it was in generator mode, and that's one reason that this sort of conversion usually doesn't make practical sense: the result is not likely to be powerful enough to be useful, which is why the examples are for bicycles and small carts.


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## Scorpio91 (7 mo ago)

Hongs Paul said:


> Hi, I heard alternators make great motors, I have one which I got from a gasoline genset and now would want to turn it into a motor, how do I do it?
> View attachment 124266
> View attachment 124268
> View attachment 124269


Listen the old GM Delco Remy alternators were wound in series ore parearel configuration to achive generator/starter effect they simply do not use bridge rectifier at all those 3 wires are simply put together and the 2 pairs of field windings 1 is put at baterry terminals the other terminals from the secundary alternator field winding are shorted together so basicaly you run ac generator to indction motor ore it will became syncronis motor .
There is posibility to turn alternator to bldc motor as well.
Back in the old days peopel used 1 dead lead acid baterry and 1 charged and they used dc motor like starter motor from a car they used only the polarity difference from that starter motor to desulfate baterrys .
So high voltage is flowing to low voltage so if the starter motor stops simply swap the leads over to go same direction ore have swichabel gear box.
You can use transformer ,baterry and 1 dc motor as well.
So I understand what you want .
It does exist as long you have voltage potential difference the electric motor will spin .
So you need switching circuet to reverse voltage and current flow when you sicesfully transfer power to dead baterry simply reverse it again and again .
So thats the john bedini circuet .
North East starter generators used such methodes they are called compound sg's.
Delco hade rotary converters inverters and transformers it was comon in the old days to use 4 commitator rotors so indead you culd gave dc + dc - ac and ac out of phase so basicaly it is posibel.
Ither way useing just ac ore the old compound dc sg's worked that way by useing just voltage potential difference.
Lead acid baterry if it has greater voltage potencial after some time it becames thermal baterry who reacts to enviroment chamges aka weather conditions.
So your baterry holds charge and discharges faster at low temperatures.
So please see the old SG's how they were designed ,ore use 2 car delco alternators they hade bypass wires on their voltage regulators.
I hope this help you some what.
Compound sg's work with compound multi stroker engines be awere of that fact they have closed loop egr system and they have fuel recovery system by useing bacteria .
The exaust system was chemical to chemical conversion methode .
Those same compound engines used dual ignition .
So thats what you are after .
Use modified hit and miss engine stile with ethanol/methanol vaporisation not injection.
Ore use wind ore water with tesla pumps to air your compound sg's.
Thats proper way how you wuld achive power regeneration.
Be aware only thing you can alter are bacteria and elements .
Evry thing ells are methode of conversions!
For me thats ordinary clock works.
See please how papp engine work ore lanz bulldog tractor piston lock how it works.
Then you will understand how to modify hit and miss engine with compound sg's assistance .
So hope this helps you some what to understand how it can be done.


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## brian_ (Feb 7, 2017)

Scorpio91 said:


> Listen the old GM Delco Remy alternators were wound in series ore parearel configuration to achive generator/starter effect they simply do not use bridge rectifier at all those 3 wires are simply put together...


Since this makes no sense at all, I think the best approach to this post is to just ignore the whole thing.


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## Girolamo (3 mo ago)

Hello My name is Fabio, I am Italian. I am interested in mini wind turbines, I came to this forum by googling modified car alternators.
I am making a mini domestic wind turbine, I have a problem that I have to start the rotation because it has no torque when standing.
So i was thinking of using an esc to run the alternator as the engine for a few seconds. My question is: do you think I have to remove the rectifier bridge anyway? I would like to leave it with the three-phase esc I can still wire the windings directly. Obviously when I use it as a motor I disconnect the DC connection with the load, which is the reverse when it becomes alternator.
Thank you for your professionalism and sorry for my English.


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## remy_martian (Feb 4, 2019)

You can spin up a 3 phase permanent magnet motor and use it as a generator. Most inverters will do this on their own and no disconnect is needed - a small amount of overspeed will push power back into the battery.

Your challenge is having it operate at its maximum power transfer point, which likely needs some bespoke circuitry and software, unlike what we do here by commanding torque/regeneration with a throttle pedal.


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