# Rebuilding motors



## Kempie9901 (Sep 12, 2009)

I have an ac motor 10hp 1750 rpm, that was given to me but it was supposidly fried. is it possible to have somebody rebuild the motor and change it to a dc motor? or is it possible to change the power output?


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## yarross (Jan 7, 2009)

Kempie9901 said:


> I have an ac motor 10hp 1750 rpm, that was given to me but it was supposidly fried. is it possible to have somebody rebuild the motor and change it to a dc motor?


DC? I don't think so. You would need a completely different rotor, and distributed stator windings are not optimal for this motor type. Economical nonsense.


Kempie9901 said:


> or is it possible to change the power output?


You can get this motor rewound for higher rated speed. This would yield some increase in power, maybe up to 2 times, but rotor strenght is a limiting factor.


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## Kempie9901 (Sep 12, 2009)

Well it would be easier to use a DC motor instead right? So i need to go and find A good DC motor to use?


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## yarross (Jan 7, 2009)

Kempie9901 said:


> Well it would be easier to use a DC motor instead right?


I can just say turning AC motor into DC (or vice versa) is not an option 



Kempie9901 said:


> So i need to go and find A good DC motor to use?


This is the cheapest way.
There are some projects using industrial induction motors of this power range.
My favourite one is http://rc-autopilot.de/wiki/index.php/Opel_Corsa_Project .


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## Kempie9901 (Sep 12, 2009)

Pretty good stuff, but i think i will get a motor off ebay. I found a 18.2 kw 925 rpm motor for $250, which sounds like plenty of power, i will just need to change the axle ratio for top speed. Thanks for the help!! It is very appreciated. Need all the help i can get!!


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## yarross (Jan 7, 2009)

Kempie9901 said:


> I found a 18.2 kw 925 rpm motor for $250, which sounds like plenty of power


Low RPM -> high weight.
High power + low RPM -> very high weight.
IMO 4pole motor is optimal.
There's a reason that almost all production drive motors are of 10000rpm and higher.


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## Amberwolf (May 29, 2009)

Kempie9901 said:


> I have an ac motor 10hp 1750 rpm, that was given to me but it was supposidly fried. is it possible to have somebody rebuild the motor and change it to a dc motor? or is it possible to change the power output?


First, how many wires come out of it? "AC" doesnt' necessarily mean it is a multiphase motor, based on nameplate markings. 

If it is indeed a multiphase AC motor, then making it into a single-phase (DC-capable) motor is probably impractical. 

If it's 1750RPM, that sounds like a single-phase induction motor, so probably you could rebuild it to make a DC powered motor out of it, but it would probably cost more than buying the type you actually need, if paid someone to do it for you. Doing it yourself, on the other hand, could be pretty cheap if you look hard enough for the parts and have the time on your hands already.

Also, what do you intend to drive with it? At only 10HP, it doesn't sound like it's powerful enough to move most EVs very fast (seriously, maybe creeping down the road, depending on the gearing you use), though some bikes (bicycle or motorcycle) could move pretty well with one that small.
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## yarross (Jan 7, 2009)

Amberwolf said:


> If it's 1750RPM, that sounds like a single-phase induction motor


Why? It's probably a regular 3ph 60Hz 4pole motor. 1ph motors are very rare with power ratings above 3HP.


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## Amberwolf (May 29, 2009)

yarross said:


> Why? It's probably a regular 3ph 60Hz 4pole motor. 1ph motors are very rare with power ratings above 3HP.


OH. I only thought about the speed part of it. My bad.  I'm certainly no motor guru.
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## Kempie9901 (Sep 12, 2009)

yarross said:


> Low RPM -> high weight.
> High power + low RPM -> very high weight.
> IMO 4pole motor is optimal.
> There's a reason that almost all production drive motors are of 10000rpm and higher.


Well does this mean that it will weigh too much? 350 lbs too much? If not then would i be able to change my axle ratio enough to compensate for the low rpm of the motor?


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## yarross (Jan 7, 2009)

Kempie9901 said:


> 350 lbs too much?


It yields only 0.12kW/kg. Really poor.



Kempie9901 said:


> If not then would i be able to change my axle ratio enough to compensate for the low rpm of the motor?


I'ts possible but rather costly. Better to use existing transmission.


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