# Motor Cooling



## Renny_D (Apr 21, 2009)

I need some help with a new issue that my latest upgrade has presented me with. I've updated my 06 Zap PK from 72 to 132 volts. The car runs much better but the motor gets much hotter. Right now I have a blow through fan for cooling. In addition to this I would like to add possibly water cooling. If I wrapped the motor in a sheet of copper braised to copper tubing then used a pump and a small radiator - I have an oil cooler radiator that would be perfect for this. Would this work - meaning would cooling the outside of the motor help cool the motor as a whole? The fan cools the inside of the motor. I did a search but could not find out anything. 

On a related note - if the above works would it be possible to also have the same system heat the batteries in winter? I'm looking to drive this year round and I'm thinking of wrapping the batteries in copper tube and when plugged in using a water heater element and when on the road using the heated fluid from the motor cooling.

Last question - what is a safe temperature for a motor? What temperature would I want to have the system turn on at? The reason I ask is the oil coolers from a mazda rx7 have a built in thermostat set at 180 degrees. Below this it bypasses the oil cooler. 

I know lots of questions - I'd appreciate any help you folks could give.

thanks
Renny


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## Woodsmith (Jun 5, 2008)

Series motor I presume?

With a series motor all the heat is generated in the armature. Cooling the outside of the motor frame would have very minimal effect on cooling the armature. The simplest way of cooling it is to blow air though the core as you are doing.
Maybe increase the cooling air flow?

With an AC motor all the heat is geerated in the frame. That is why industrial AC motors often have fins on the outside but DC ones never do, they just have a big fan stuck to the side.
So, in theory you could water cool an AC motor, and some commercial ones are built that way.

That nullifies the idea of warming the batteries with a water cooled DC motor.

I have read of people using water bed heating pads to warm their batteries.


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## Renny_D (Apr 21, 2009)

Thanks for the reply. So the fact that the outside of the motor istoo hot to touch means that the inside is way too hot? I'm looking for a bigger fan right now. Any other feedback anyone? 

thanks
Renny


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## rillip3 (Jun 19, 2009)

At the risk of sounding obvious, you might want to cut back on your voltage. If it was fine at 72, but is not at 132, then cutting back until it is at a stable heat might be a good idea.


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## Tesseract (Sep 27, 2008)

Woodsmith said:


> ...
> With a series motor all the heat is generated in the armature.
> ...
> With an AC motor all the heat is geerated in the frame.


While these statements _can_ be true, note that in a well-designed motor the losses will be split equally between the stator and rotor.

The commutator heat up the quickest in a DC motor, while the rotor bars in a squirrel cage ACIM heat up the quickest (they are essentially single turn secondaries that have been shorted, not unlike a soldering gun, actually  )


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## Renny_D (Apr 21, 2009)

rillip3 said:


> At the risk of sounding obvious, you might want to cut back on your voltage. If it was fine at 72, but is not at 132, then cutting back until it is at a stable heat might be a good idea.


Thanks and I may cut back some what but I'm curious as I see folks buy old 48 volt fork lift motors then proceed to run 144 volts and more through them so they must be doing something to help keep those cool? Besides the car was a dog at 72 and even at 84 volts. Now it actually feels like a normal car as far as hills and ability to get out of its own way. If I can't find a solution to the cooling then I will go with lower the voltage but I'd rather solve the heat issue if possible.



Tesseract said:


> While these statements _can_ be true, note that in a well-designed motor the losses will be split equally between the stator and rotor.
> 
> The commutator heat up the quickest in a DC motor, while the rotor bars in a squirrel cage ACIM heat up the quickest (they are essentially single turn secondaries that have been shorted, not unlike a soldering gun, actually  )


Ok so if this is true there may be some benefit to increasing the cooling on the motor case as well??

Any more feedback would be appreciated thank you to those who have already.

Thanks


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## Bowser330 (Jun 15, 2008)

like others have mentioned, maybe a larger external fan and if you are really concerned, then maybe have a temperature controlled release of a small bottle of liquid Co2 which will super cool the air..just an idea, albeit an extreme one...


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## rillip3 (Jun 19, 2009)

If the outside is getting too hot to touch, it seems to me that it's dissipating some of the heat at least, so any cooling you can put on it should help, at least down to the point where the outside stays at room temperature.

Have you tried it at 96 or 120? Also, just putting more juice in it is not necessarily the answer. I don't know from personal experience, but it seems likely that people who are over-juicing their motors may be advancing the brushes to utilize it. If your brushes are still set the same as they were at 72v, it is probably building up a lot of resistance at the higher voltage, hence the heat. I couldn't give good advice on how much to advance or if this is actually the solution, but it gives you an avenue to research.


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## jehan12413 (Feb 4, 2010)

FYI a while ago I used a 36 volt forklift motor for testing my controllers at 72 volts. After doing several runs at several thousand amps you could feel the heat from all the cables and the commutator but it would sit for at least 10 minutes before the outside case warmed up. My point is that by the time that the heat works its way through all thet iron the windings are probably way too hot.


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## gor (Nov 25, 2009)

does air gap between rotor and stator can provide enough airflow for effective cooling?
- anyone thought about liquid cooling of rotor?


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