# Has anyone here disassembled an induction motor?



## steven4601 (Nov 11, 2010)

Nice to see your still interested in an AC motor for your project.

Have you looked into light-weigt aluminium cased aircooled industrial motors? A 15kW industrial rated motor can likely do 60+ kw for a minute or so. Driving road cars is more about delivering peak power (in a wide rpm range) than continious power. Driving the evz3 at 80km/h requires a little less than 10kw. 

What I was trying to say (again) is, not to (re)build a motor, rather choose wisely. Have you considered the EVE M3ac50/ or 60? The Wavesculptor im using is more than happy with it.


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## bjfreeman (Dec 7, 2011)

I had a company design my 200KW liquid Cooled AC motor
The squirrel cage is made of solid aluminum Bars for the windings. Since there is no electrical connection to the squirrel cage it is also hard to connect fluid through the Rotor.
The fluid flows through the outer jacket. up to a point you can increase cooling by increasing the flow of cooling fluid. and the Radiator cooling capabilities.


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## piotrsko (Dec 9, 2007)

Major has warned of cutting the motor case in a haphazard way. something to do about flux paths, but I'm not a motor expert. I do know of several attempts here on this site that resulted in a worthless motor.

YMMV


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## major (Apr 4, 2008)

piotrsko said:


> Major has warned of cutting the motor case in a haphazard way. something to do about flux paths,......


Most of the DC motors we see here use the outer shell as the yoke or back iron and it is the magnetic path. This is the stator for these types of motors and the flux doesn't change at high frequency. In the AC motors the stator is the armature and has an alternating flux at the fundamental frequency in the yoke (magnetic path) so use laminations. These laminated stator cores should not be wacked haphazardly. But most AC motors have a shell around this laminated stator core for enclosure and end bracket support. This shell is in fact sometimes non ferrous (like aluminum) or cast iron (not particularly good magnetics) or rolled steel (but likely doesn't contribute to the magnetics).


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## coulombKid (Jan 10, 2009)

major said:


> Most of the DC motors we see here use the outer shell as the yoke or back iron and it is the magnetic path. This is the stator for these types of motors and the flux doesn't change at high frequency. In the AC motors the stator is the armature and has an alternating flux at the fundamental frequency in the yoke (magnetic path) so use laminations. These laminated stator cores should not be wacked haphazardly. But most AC motors have a shell around this laminated stator core for enclosure and end bracket support. This shell is in fact sometimes non ferrous (like aluminum) or cast iron (not particularly good magnetics) or rolled steel (but likely doesn't contribute to the magnetics).


I seem to recall a few low voltage AC motors made in the UK that have the stator pressed into an aluminum shell with inner and outer walls where coolant is pumped. I've seen rotors that have holes in the laminations large enough to allow some air to pass. Many rotors have the fan blades cast into the aluminum end-rings of the conductive cage. With such a high internal reynolds number they do a good job of convection cooling both the stator conductors and the rotor windings. The materials that the rotor laminations are pressed into are not as efficient as the silicon steel used for laminations in suppressing eddy current losses. Eliminating sneak magnetic circuits from the stator assembly is one of those things the designers would examine carefully to push the efficiency of the motor higher. Getting back on track to the original poster, The currents in the rotor bars can at times be high but of low AC frequency. If you could ride the rotor with a fluke you would find a fairly low potential from end ring to end ring. The aluminum is a good conductor so high current/low voltage generates a manageable amount of heat at rated usage. When the fan blades are cast into the cage it is because aluminum is also a good heat conductor. With them spinning in the breeze at high RPM they draw the heat from the conductor bars out into the air stream where the turbulence created can dissipate the waste BTUs and on the way through also pick up heat generated by the stator windings. I would not recommend cutting off internal fan blades. A liquid cooling alternative is not really feasible in the rotor for a small motor. Some generators have been tested that have hollow conductors with liquid nitrogen pumped through them but the same researchers that would solve the plumbing nightmare would be doing it to study superconductors in large commercial generators.


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## iti_uk (Oct 24, 2011)

Thanks for the replies. I feel I should clarify my original question, since there seems to be a mis-communication here... I'm not looking to liquid cool the rotor, only the outer jacket/casing. I am imagining that, in a water-cooled jacketted induction motor, heat is transferred from the rotor to the stator (radiation, convection, etc.) and that the rate of heat transfer in this mode would be sufficient for keeping the rotor within acceptable temperatures. Is this assumption wrong - is fan-induced airflow over the rotor absolutely necessary?

The motors mentioned which have the stator pressed into an aluminium or non-magnetically-important (ye, down with the lingo!) iron/steel case would be the sort of thing I am after, where the working parts of the motor can be removed by disassembly/machining and where the casing design or material is fairly arbitrary in everything other than cooling capability.

The EVE M3ac50 looks like a nice motor, but over-powered for what I want. I'm looking for something more in the 15 to 20kW range with water-cooling, and I can't find anything like that anywhere. Since I am hoping to use multiple motors, keeping individual motor mass down is a priority, although I understand that squirrel cages are far from being lightweights.

An advantage of going with a custom case is that I could try something a little whacky, like two sets of stator/rotors (two motors) back-to-back in the same water-cooled case. This might be lighter than having two completely seperate motors back-to-back, may simplify cooling (fewer hose connections) and might may mounting simpler and lighter (a bracket on each end of the "sausage", rather than two mounts per motor (I'd be uncomfortable about hanging a motor simply off an endplate without support for the body of the motor). Or it could be a stupid idea, who knows until you try, eh?

I might experiment with a couple of washing machine motors (some are AC induction now...) to try a proof-of-concept design.

Chris


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## peggus (Feb 18, 2008)

I was thinking about doing something similar using a Siemens Spindle motor. These are similar to the EV motors used in the ford rangers except they are air cooled. 

The 132 frame 310lb beast I was looking at had a rotor that weighed 80lbs and stator of 117lbs. There are also shorter versions of this motor that are lighter. 

The housing is aluminum already and has air cooling channels in it, the end bells appear to be cast iron. I was contemplating machining some new end-bells in aluminum and running liquid through the housing for additional cooling. 

To find these, search Ebay for Siemens motor 1PH6* or 1PH5*, 
The 1PH7xxx and 1PH8xxx appears to have steel housings and are of course heavier. The first two xx in the part number is the frame size and the last x is related to the length.

Ultimately I decided against it as it is way too much work and the windings in these motors are so heavily varnished that it'd would require a complete rewind to get it down to voltage where I can use it. 

Here are some pictures of a disassembled one.


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## iti_uk (Oct 24, 2011)

Ahh thanks for that, peggus.

I've got plenty of experimentation to do now. Bought myself an oscilloscope and a bunch of bits and bobs to start messing with controllers as well as motors...

Chris


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