Cooling Hub Motors

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As hub motors get made to handle several thousand watts,
they generate more heat. However their surface area and cooling capacity do not appear to be increasing enough. Rarely does one see cooling fins on the hub motors.

Has anybody found nice, effective ways to insure sufficient cooling for these motors?

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Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

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Mik
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Re: Cooling Hub Motors

The Vectrix motor has cooling fins.

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Re: Cooling Hub Motors

Well the motor is already in the air flow...so...?

Adding a heatsink to the motor would make it wider and require a wider fork, right? There's a geometry problem here.

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Re: Cooling Hub Motors

Mik wrote:

The Vectrix motor has cooling fins.

In Gary's context a "hub motor" is one that is "inside-out" the windings are inside (in the RC world they call them out-runners rather than in-runners).

The Vectrix has a conventional motor mounted in the swingarm and directly connected to the rear hub (which contains a single ratio planetary gearbox with a reduction ratio).

The issue with a hub motor is that the windings are inside and they're the part that generate the most heat. It's fundamentally much harder to cool this "inside-out" setup.

On the Vectrix the windings are on the outside (not exposed, but on the outside in relation to the magnets). This makes it much easier to get airflow and thus cooling.

Thus cooling a Vectrix motor is easier than cooling an XM motor. (Also the mighty V has mechanical gearing on it's side whereas an inside-out hub motor has no gearing other than changing the rolling circumference)

Putting fins on the outside of a hub-motor may help a little but not as much as on a standard motor.

Another approach to reliability is rather than cool it more make it more robust to higher temperature usage. Cooling is the better approach but you might find it difficult.

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Re: Cooling Hub Motors

I have been working on a large hub motor design for motorcycle conversions called the MHM-602. In trying to get 10KW continuous out of the first prototype I ran into a heating problem and decided to force air cool the motor while waiting for 2 new improved designs to arrive DSC_0235_S.jpgDSC_0237_S.jpg
This made a huge improvement in heating and since implementing this fan cooling have not had one temp shutdown using the Kelly thermistor input set to 135 with the sensor in direct contact with the winding. I've since showed this technique is possible with an X5 motor
DSC_0231_S.jpg

If you want to pull many KW with an X5 holes in the covers (with screens) and fans will let this motor reach 3 to 5 KW without overheating

Mark

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Re: Cooling Hub Motors

Good ideas, Thanks.

What "glue" did you use to attach the screens?
What material and mesh are the screens?

How did you attach the fans?
How did you power them?
Did you choose any special fans (high flow, etc.)?
Where did you order/get them?

Any more details that you would like to share would be welcome.

The motor on the XM-5000Li is only about 8.3 inches in diameter, so I might need to try using rather "small" fans.
I might try adding some "scoops" on the left side (where there is about an inch of external clearance) to help force the air into the motor, and then fans to force the air through and out the other side.

The possibility of picking up iron "dust" that would build up on the magnets is a concern of the motor maker. A forced-coolant (into and out of the axle) design might be an interesting option, especially if the circulation pump (if electric) only runs when the motor is warm.
The tubing might be flattened on one side to provide for better thermal contact inside the motor, and so that the in and out tubes can better use the same hole through the right end of the axle.

Or, perhaps going to some non-conventional, easily-replaceable "brushes" or contacts on non-segmented slip rings on the inside of the motor would work with the 3 (or 6) phase motor?
The Hall effect devices could be on the stationary side, with some small magnets added to the rotating side?
Just random ideas, but more cooling is certainly needed in the motor design.

Thanks for your input and the pictures.

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Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

markcycle's picture
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Re: Cooling Hub Motors

garygid wrote:

Good ideas, Thanks.

What "glue" did you use to attach the screens?
What material and mesh are the screens?

How did you attach the fans?
How did you power them?
Did you choose any special fans (high flow, etc.)?
Where did you order/get them?

Any more details that you would like to share would be welcome.

The motor on the XM-5000Li is only about 8.3 inches in diameter, so I might need to try using rather "small" fans.
I might try adding some "scoops" on the left side (where there is about an inch of external clearance) to help force the air into the motor, and then fans to force the air through and out the other side.

The possibility of picking up iron "dust" that would build up on the magnets is a concern of the motor maker. A forced-coolant (into and out of the axle) design might be an interesting option, especially if the circulation pump (if electric) only runs when the motor is warm.
The tubing might be flattened on one side to provide for better thermal contact inside the motor, and so that the in and out tubes can better use the same hole through the right end of the axle.

Or, perhaps going to some non-conventional, easily-replaceable "brushes" or contacts on non-segmented slip rings on the inside of the motor would work with the 3 (or 6) phase motor?
The Hall effect devices could be on the stationary side, with some small magnets added to the rotating side?
Just random ideas, but more cooling is certainly needed in the motor design.

Thanks for your input and the pictures.

What "glue" did you use to attach the screens?
Silicon glue works

What material and mesh are the screens?
Nylon standard bug screen but not metal

How did you attach the fans?
drilled and tapped holes

How did you power them?
My motorcycle is grounded with respect to the 12 volts so I tied the negative lead to the stator frame and brought out 1 wire for the 12 volts

Did you choose any special fans (high flow, etc.)?
Ball bearing fans good quality fans around 7cfm each

Where did you order/get them?
Ebay of course
http://stores.shop.ebay.com/Lumpy-Oats-Computer-Parts__W0QQ_armrsZ1

I really don't think iron dust is a big problem at least with a motorcycle using 18 rim the hub is far off the ground. I would rather have to clean out the hub a few times a year then be on the side of the road waiting for the motor to cool. Also you can use foam over the holes to keep out debris and or put a small magnet in the center of the hole to attract and hold iron dust from getting into the motor. I have no idea if there is room inside your motor and if the stator would allow air flow through it but if it would then this is a simple idea that works

this is a picture of the motorcycle with the hub motor before I put in the fans
DSC_0189_S.jpg

Mark

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Trying to Change the old school ways of doing things
But I never Never try to break the laws of Physics
http://www.doingitall.net/EnerTrac

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Joined: 12/20/2008
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Points: 441
Re: Cooling Hub Motors

Mark,
Thanks for the info.
Now, I need to see how much space is available inside the 5000Li's motor. Maybe three 40mm square x 10 mm thick, 12v, dual ball bearing, 9 cfm fans will work.
Thanks again.

__________________

Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.

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