Hi every one
I have a combo of Emax motor 2215 and Turnigy ESC 30 amps  and a prop of 10 in
Every thing is just according to recommendations... But after about 5 min of flight the motor and ESC become Hot ... I mean the motor is real hot .... And Batteries are warm .....
I actually tried the combo with out load that is with out prop ... The motor is Hot ESC is warm


Any reasoning .....

Overpropping,
can you give a link to the motor.

Ashok.P

The recommended prop is 7 to 10

Better link ..
http://www.emaxmodel.com/views.asp?hw_id=38

Use 9 inch ep prop and 20 amp ESE 11.1 v batt

I have same combo for my sbach. U can see pic in my post on electric plane.

@kewal ... I won't get the desired thrust with a 9 in prop

Try running it with no prop on a 20A esc, if it still gets hot then its faulty. else overpropping is your issue.

Ashok.P

Tried running it without prop on 30 A ESC still gets hot

Should be a problem with motor or ESC, if your ESC is programmable then set all the values to default and try again,
One question here, is it warm or hot, most ESCs get warm with a 5min run but not hot.
Possible checks, see if the motor can is rotating freely, turn it with hand to hear the sound, any metal sharpnels can cause this problem.
inspect clearly under a bright light to check for motor can and armature friction.
also try interchanging some other ESC or motor to see which one is faulty.
Good luck.

Ashok.P

I have used the same ESC with a iPower 1250 kV motor without any problems ... And the ESC was hot ( it melted the epe foam used as packing ) and motor rotates freely no issues such as friction or noise ....

And to end its a brand new motor ..
 I guess I have to discard the motor

These points seem to be missing from the discussion.

1. Everyone talks about the size of the prop, not the pitch ! When a motor manufacturer says 7 to 10 inch prop, it should also be understood that as the size increases, you should reduce the pitch to prevent overdraw of current and heating issues. One cannot arbitrarily keep on increasing prop size just because "I need more thrust", without worrying about pitch and/or corresponding current draw.

2. It is a bad idea to run motors under no-load (no prop) for extended periods.

3. The statement "I won't get the desired thrust with 9" prop" is a clear indication that you are border-line in your power setup, which means the AUW of the plane might be too high. Always plan for power systems with enough leg room based on your model weight and flying performance required.

On park flyer size motors, roughly 45 to 79 gr weight, whenever there is a wide range of suggested prop size such as 7 to 10 inches, it means smaller prop on 3S or 4S lipo, and the bigger when using 2S lipo.

each motor is also rated to handle a maximum value of watts.  You can burn a motor even before the maiden flight during static tests if you're not careful.

I had a nice Exceed RC 370 brushlesss motor with only three flights on it.  I did everything right except fully tighten the prop adapter.  The cone/nut backed off which caused the shaft to spin without a load.  This was a case of having no prop yet the motor burnt out.

The best way to be sure is to use a watt meter.  You can see the watts and amps usage throughout the throttle range.

ranging from 2 to 8 or 10 power transistors or FETs are connected in parallel inside the esc to increase output current , failure of even 1 or more FETs will increase the load on other FETs , so they tend to heat quickly.

check for any such damage/failure inside esc.

I do not understand one thing, if there is no load there should be less current flowing through the circuit and the back EMF should be almost equivalent to the supply, but how come a brushless motor burn out with no load.
( i personally had my emax 2812 motor without prop for long time and never got warm to tough/overpropped it with 10x7 prop and it boiled out but was working fine until the wiring snapped)

Ashok.P

at high rpms(means high frequency at o/p terminals of esc) , does it have to do anything with inter electrode capacitance/inductance.....??

too much heat buildup results in high temps enough to damage

One second of WOT without a prop probably won't burn a motor but try 10 seconds will

Best Answer from Chriss:

chriss
Senior Heliman
Sunny Florida

 No high performance motor should ever be free run for more than a few seconds at a time. The motor will draw a minimal amount of current once threshold voltage is reached. This power is not being dissipated through the shaft via mechanical work so it has to be dissipated in heat through the case of the motor. The net result is that the motor will become over heated in a short amount of time.

Yes, Kv is the rpm/volt of the motor. It and Kt , the torque constant (in*oz/amp), are related through the constant 1355. If you know one you can determine the other mathematically. Kv*Kt=1355

In a brushless motor, there is really no reasonable upper limit to rpm. The only things limiting it would be from the centrifugal force on the rotor wanting to throw it apart or the bearings. If the motor is well balanced and solidly constructed, it should be capable of very high rpm's.

It is always best to setup an electric motor system so that most of the time the motor is at full throttle. This is due to the inefficiencies of the speed controls when opperated at part throttle loads. But, the motor also has a happy current it wants to run at. When setting up a new system, you should always endevor to keep the motor loading close to the maximum efficiency point on it's load line.

Check the Aveox site for some good info. Also Astro Bob's motor handbook is a good source of info. Most of it is about brush motors, but the info is pretty universal.

Chris

I think you can use 10x4.7 prop for good thrust with 30a ESC.
One more thing, air ventilation is also necessary element to cool electronics.Did you balance your prop? Is your plane scratch build? What is weight? can you post pics here,,

@docnayeem
Buy or borrow a wattmeter.
Without power reading, these discussions lead nowhere.
But motor hot, esc hot, battery warm all indicate overload.

@docnayeem
Which 2215?
What pitch?
What rpm on full throttle?

wat thrust u want?

Use only 20 amps .30 amps is not suggested from my side.

Care:
Emax's own data (rpm on 10x6) seems suspect or misprint