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#1 whosthebaddest Jun 20, 2012 06:58 PM

Question about ESC effect on motor temp
 
Hey guys. I have a flying wing and I was trying to get a fast setup on it with a 3648 1450kv turnigy on 4s and a 9x6 prop.

It pulls over 100 amps for sure. I was using a hobbywing 100-120amp ESC and its not cutting it. Sometimes it works but frequently cuts out when it gets too hot.

I totally friend and smoked one of these motors with a 10x7 prop LOL the motor burnt to a crisp but the ESC was ok? go figure?

so aiming for the 9x6. Even with the 9x6 the motor gets VERY hot. Not hot enough to burn on touch but close hot enough so you can only tap it really quick with your finger. The ESC was hot also. It was a 90 degree day also all things considered.

I don't want to run a motor too hot for obvious reasons (ie don't want it to go bad when not expected)

My question is if I get a better ESC that can handle 200amp would this cause the motor to run cooler?

Also I'm using turnigy nanotech 65-130C batts If I use say 30C batteries instead of 65c batteries will this
decrease the motor temp also as well?


Thanks for your help!! :)

#2 Lnagel Jun 20, 2012 08:08 PM

The motor heating up is caused by the motor pulling too much current. The ESC has nothing to do with how much current the motor pulls. So changing the ESC will accomplish nothing. The motor's current pull is caused by the load on the motor, which is the propeller. The way you decrease that load, which decreases the current and thus the heat, is to either use a smaller propeller or spin the propeller slower by lowering the motor's applied voltage, i.e., lose a battery cell.

Larry

#3 Bruce Abbott Jun 21, 2012 02:57 AM

Power loss is proportional to current squared. Your motor is rated at 70A for 20 seconds. At 100A it has to dissipate twice as much heat as it does at 70A. No wonder it's getting hot!

You should drop the prop size down to 8x6, or even 7x6. I bet it won't be much slower with these props (perhaps even faster if your airframe is slick enough), but the motor and ESC will stay much cooler.

#4 whosthebaddest Jun 21, 2012 04:14 AM

Cool thanks for the help Guys!!

#5 jackerbes Jun 21, 2012 06:14 AM

An alternative, since you are looking for a "fast setup," is to add a motor that can handle that much power. If you drawing 100A at 15V you want a 1500 Watt motor. That would weigh about 300 grams.

If the 10 x 7 prop is a limiting factor (you cannot fit a larger prop) you want to spin that at a max RPM of about 14,000 RPM (the prop's RPM limit). So you'd want a 300 gram motor with a 1600 or so Kv.

Then look for a big wide open area to fly in, a place with nothing or no one to run in to because you'll have a potentially lethal flying wing... :eek:

Jack


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