# How hot are your motors running?



## Carroll_1 (Dec 18, 2007)

92 Toyota Tercel conversion with Impulse9 motor, 1000A controller, 144V with (12) 12V gel batteries. Last summer I recorded a series of tests conducted over a week while recording battery, motor, and controller temps. After testing by running 16 miles at 55-60 mph on two lane highway, I was seeing repeated and consistent motor temps of 50C throughout the week. I measured with an infrared thermometer at the motor case, field frame bolts, and the terminal posts. Ambient temps during the week were 70F - 85F and had no effect on the operating temps.

(Note: the higher ambient air temps did increase the the vehicles range about 2 miles per test by increasing the battery operating temps.)


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## Snakub (Sep 8, 2008)

My Warp 9 with 168 volts nominal to it in the summer only gets say 120 F. What kind of conversion are you running with this BLDC motor and how many volts are you applying? Do you have any kind of cooling at all to it? Blower? Liquid cooling? I thought about wrapping a heat sink with liquid cooled channels around mine.


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## david85 (Nov 12, 2007)

The motor is a TEFC with an integral fan, but I'm wondering if I need to direct some more air flow to it. The space its intalled in is very tight but it is exposed underneath.


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## DavidDymaxion (Dec 1, 2008)

Not as scientific, but a rule of thumb I've heard is you should be able to put your hand on the motor. I've had mine hot enough I couldn't keep my hand on it for more than one second. It didn't seem to hurt it, but at that point I'm looking to cool it down. It seems to take forever to cool it once it gets hot. The first couple of times I got it hot it smelled, but that stopped, I assume it was initial outgassing.


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## etischer (Jun 16, 2008)

david85 said:


> I'm using an infra red thermometer to measure the temperature of my motor by reaching under the car and shooting it (after pulling over) and after a successful motor controller mod, I've gotten the outside of the motor as hot as 87C. Anyone think this is too high? The insulation rating of the motor is supposed to be 155C.



The outer casing of the motor, the part you are able to touch and measure with an IR gun is probably a bit cooler than the internals. The middle of the coil windings are sure to be hotter.


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## dimitri (May 16, 2008)

DavidDymaxion said:


> Not as scientific, but a rule of thumb I've heard is you should be able to put your hand on the motor. I've had mine hot enough I couldn't keep my hand on it for more than one second. It didn't seem to hurt it, but at that point I'm looking to cool it down. It seems to take forever to cool it once it gets hot. The first couple of times I got it hot it smelled, but that stopped, I assume it was initial outgassing.


I have had exactly the same experiences. My Warp9 motor typically gets to 70C-80C, too hot to hold the hand on it, but otherwise seems to handle it without issues. It has over 13,000 miles on it by now.

If I recall, the spec states 120C limit for Warp9, but its not clear at which spot this temp limit applies, brushes/commutator or outside case or else.


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## david85 (Nov 12, 2007)

etischer said:


> The outer casing of the motor, the part you are able to touch and measure with an IR gun is probably a bit cooler than the internals. The middle of the coil windings are sure to be hotter.


I agree the internals are likely hotter, but at the moment I have no way of knowing how much hotter. Unless there is a general rule I can look up??


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## corbin (Apr 6, 2010)

I think my Warp9 was getting up to 50-60 C after 30 mile drive (including a large hill). I'll measure it again (also with a infrared thermo) and report back. See my blog link below for my car stats. (Short: Bug, Warp9, Netgain Warp Drive, limited to 600 batt amps, 154v lithium, 200ah)

corbin


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## steven4601 (Nov 11, 2010)

Hi David,

If it is an BLDC you want to keep the magnets as cool as you can without taking weird measures. simple air duct can be enough.
Is it an out-runner or in-runner? If 80C is the magnet temperature you are stress-testing it. If 80C is the stator temperature you are okay. Place a thermocouple between the windings. Maybe the eddy currents prevent from measuring while the motor is spinning but it should give exact winding temperature measurements when pulling over. 




Steven


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## david85 (Nov 12, 2007)

Thanks for the input guys.

Steven, the motor is an in runner, and the temperature is taken of the outside of the stator (outside case) after parking the car. 

What I'm unsure of with this type of motor is if the permanent magnets generate their own heat, or is all the heat coming strictly from the windings?

Interesting point about using a thermocouple. I plan to have a temperature gauge in the car eventually but right now all I have is a small pocket IR thermometer.


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## steven4601 (Nov 11, 2010)

Hi David

That is quite a good question. I cannot imagen the magnets staying cool from constant flux variations working on them. Eddy currents within the metals should heat it up. Im goin to think about this, as I also want to know the rotor temperature of my AC motor while its spinning. Maybe hacking an IR thermal camera or a thermopile sensor and build it into the motor is an easy solution. 10C accuracy is good enough for damage assessment. 

Something you may already know but like to share it with you:
At work I had the oppertunity to try out various heatsources and their materials. Most materials work well with IR based sensors. However brushed Aluminium is like a mirror for those IR thermal cameras or meter devices. Can see other heat sources by reflecting the heat on brushed aluminium as an image! I assume your motor is coated and should work quite good with an IR thermometer.


//Steven


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## david85 (Nov 12, 2007)

Yeah, the motor is coated in insulation, then painted. The frame is also cast iron so getting an IR reading shouldn't be a problem.

I'm just trying to figure out if the magnets are likely to be hotter or colder than the stator. Logically, I don't *think* they would generate as much heat, but at the same time, its completely surrounded by the stator so whatever heat gets there has no real place to go.


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## rochesterricer (Jan 5, 2011)

You might find it useful to check out RIPPERTON's e-motorcycle thread. He is running a brushless PM motor and recently toasted the magnets by overheating them. He first describes the issue on this page:

http://www.diyelectriccar.com/forums/showthread.php/ripperton-electric-track-bike-41173p19.html


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## david85 (Nov 12, 2007)

rochesterricer said:


> You might find it useful to check out RIPPERTON's e-motorcycle thread. He is running a brushless PM motor and recently toasted the magnets by overheating them. He first describes the issue on this page:
> 
> http://www.diyelectriccar.com/forums/showthread.php/ripperton-electric-track-bike-41173p19.html


Thanks for that.


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## corbin (Apr 6, 2010)

An update: my warp9 after driving 30 miles at 60-70 mph, including a ~7% grade at 55mph for about 10 minutes: 60 C when pointed at the brushes, and 70 C when pointed at the case. Outside air temp: 18 C. I think 70C is the hottest it has gotten.

So, in general, my motor seems to run 50 C - 70 C.

corbin


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## corbin (Apr 6, 2010)

corbin said:


> An update: my warp9 after driving 30 miles at 60-70 mph, including a ~7% grade at 55mph for about 10 minutes: 60 C when pointed at the brushes, and 70 C when pointed at the case. Outside air temp: 18 C. I think 70C is the hottest it has gotten.
> 
> So, in general, my motor seems to run 50 C - 70 C.
> 
> corbin


Today was hotter. It got up to 80C on the same drive home; although, I pushed it a little harder, and measured it at the top of my hill before a 2 mile coast downhill.

corbin


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## david85 (Nov 12, 2007)

Thanks for the update. On the drive when I got it to 87C, I was sustaining about 70 MPH on some shallow rolling hills. I'm not positive of the speed though since the car came with slightly oversized tires and the speedometer is likely reading a bit low (guessing 9% but not sure).

Thinking to give it another run to see what happens.


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## corbin (Apr 6, 2010)

My 80C read was after sustaining 65-70 for about 20 miles, and then 55 up a 5-6% grade for 5 miles.


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## david85 (Nov 12, 2007)

Well I just got back from a ~50km run sustaining similar speeds. I stopped half way at a turn around spot and checked the motor - 66C

Turned around and headed back. For the last few clicks on the freeway I let it top out in 4th and I think I might have hit 75 at one spot (I need a GPS!). Power on the EV display maxed out at 25-26kw.

After pulling into the driveway I checked the motor again and it was at 82C. I think I'll have to pick a specific speed and kw output range and let the car cruise at that for a longer period to see where the temperature settles. at 22kw output it was holding 65-70 for most of the time but I need a longer test run to be sure.

I should also add its still cold up here. About 5C outside, which is why I thought it was safe to test it this evening without fear of burning anything up.


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## dtbaker (Jan 5, 2008)

after normal driving around town... which averages around 35mph, so not a LOT of air blowing by open underneath, the casing seems to end up around 130-140 deg F. This is with 8" motor, 120v pck and curtis 1221 controller.


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## ciggy (Mar 24, 2011)

In theory it's possible to calculate the temperature of copper coils by comparing cold and hot resistance measurements but for such heavy coils it probably requires a very good meter with an accurate low ohms range. The thermocouple suggestion is probably much easier.


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## tomofreno (Mar 3, 2009)

The hottest I've seen my HPEVS AC50 is mid 60's C. That was after climbing about 4500 ft elevation, about 19 miles of 4.5% grade, at about 45 mph, with outside temperature of mid 30's C in the valley, mid 20's C at the top. It usually gets to the high 40's to mid 50's C driving mixed highway/city in the valley with outside temperatures of upper 30's C. It runs a several C cooler if I keep rpm up around 5 - 6k compared to 3-4k rpm in a lower gear. I assume due to the higher speed of the internal fan. Current draw is about the same in both cases.


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## david85 (Nov 12, 2007)

Wow, you guys have some crazy hills to deal with!


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## david85 (Nov 12, 2007)

Little update on this.

I decided to remove the plastic forward inner wheel well of the car on the right hand side. Really easy since its all snap together plastic (no tools required).

Anyway, the idea was to expose the tail of the motor so it can draw air from slightly forward of the axle whereas before, it was largely sealed off due to such close clearances. Did this and tested the car at speeds between 100-115 KPH indicated for roughly 50km.

Usually that puts me close to 90C but this time the outside motor temp seemed to be a good 10C lower - great.....then when I aim a flashlight into the wheel well to inspect for any evidence of crud getting to the motor from the tire, I see the motor fan has been damaged.

All the blades of the fan are missing and likely on the side of the road somewhere but as for when it happened, I have no idea. I drove the car again today and temperature was still reasonable and never got above 70C (I'll have more updates and photos on today's trip on my main build thread). So in other words, I've likely been driving it for much of this time without any forced air cooling at all. 

I think I found my problem


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