Smart active cooling

[helpfulguy]

I thought about this, and throwing it out there:

Resistance goes down with temperature, so a motor is more efficient when cold. A 40C motor have 25% more resistance/loss/heat generation than at 10C (source: http://www.stereophile.com/reference/1106hot/)
Also it can take more power before overheating at all.

These two effects work in synergy, amplifying each other. Also, lower temperatures mean better reliability.

I figure, keeping a low temp is great - simple as that.

I got this idea for cooling:

Mount an alu/copper cooling plate to the motor with thermal paste for best conductivity. This is the motor plate.
On this motor plate, mount multiple peltier elements with thermal paste - these are flat modules that when powered, transfer heat from one side to the other. They are very cheap and compact.
On the heated side, mount another alu plate heatsink and optional fans - or use vehicle wind drag to remove the heat from the fins. This is the heat plate.

Here is a low cost $30 package of 10 elements: http://www.aliexpress.com/item/Wholesale-10Pcs-lot-12V-6A-72W-TEC1-12706-Heatsink-Thermoelectric-Cooler-Peltier-Cool-Plate-Refrigeration-Module/1888953613.html
Sandwitch these 10 between the motor plate and the heat plate, and it will keep the motor very much colder than without. Preferrably making sure the hot air from the heatsinks does not enter the motor.

With peltier modules $30 and 2 alu plates $20 and a couple of fans $10 you basically have frosted your motor. Simplified, a 90% efficient 5kw motor will generate 500w of heat when at 40C. Lowering temp to 10C will increase efficiency to 92%. The package example can remove about 750w of heat, and can be temperature sensored, keeping the motor even COLDER than ambient temperature, actually slowly reaching lowest temp of the peltier modules (-3 degrees celsius for these modules i think). So instead of heating your motor during bursts, reaching for example 60C (88% efficiency), you keep it at around 0-10C between bursts, increasing efficiency by "up to" 93%. Cost for this is only $50.

This WILL result in longevity of motor.
This WILL result in more motor power continuous.
This WILL result in longer motor power bursts.
This MIGHT result in a total power loss (while motor power increased) (increased motor power < cooling power required) - but even then you get more bang out of your motor and might get a total value gain.
This MIGHT even result in a net gain of energy (decreased motor energy loss > cooling energy required)

So, any of you smart guys modify the calculations from my hip-shotted ones, we can decide if this is a good idea or a bad idea?

 

[jeffpetersen]

On each 1 watt of removed heat peltier module generates roughly another 1 watt of internal heat. So that after peltier (on its hot side) you will need to remove twice as much heat. That makes your system much less efficient.
I think the main usage of peltier modules is precise temperature control. And there is a price to be paid for that precision-generation of internal heat in peltier module itself.

 

[izeman]

peltiers have been identified as a BAD idea to cool motors/controllers what ever. there main purpose is not intended for ebike use.

 

[Punx0r]

I think you should try this experiment and share with us your results. Then you can confidently state what it "WILL" do

One thing to bear in mind is that rate of heat loss from the motor is dictated in part by the difference temperature between the motor cover and the atmosphere (Delta-T). So while a hot motor does have more resistance loses (bad), it does increase the rate at which it can shed that heat to atmosphere.

 

[helpfulguy]

Great - then the idea is scrapped!

 

[helpfulguy]

I think you should try this experiment and share with us your results. Then you can confidently state what it "WILL" do

Well, idea was posted for it to be discussed, only a retard would buy stuff and experiment first and think last. Thanks to our collective expertise we only had to think, no experiments needed - saves our community time. If every guy who come up with in idea should challange it in solitude, well, it's just ineffective evolution of shit.
Anyway, the idea is scrapped! Good feedback everyone - this is how we evolve!

 

[John in CR]

Electric motors are efficient enough that properly implemented air cooling is the "smart" way to go about it. That combined with using a motor of sufficient size that it's not stressed doing the job you ask of it. 8)