Outrunner Motor Timing Q's

[GeneR]

Good Evening Everyone!

I am trying to understand how to set up my speed control for my outrunner motor. Here is the setup.

BPhobbies outrunner 2820-6, 1000 rpm/v, 14 pole being used with 11x6 prop and 3 cell 4200 lipo. Speed control is BPhobbies 45 amp. There is a motor timing setting which can be set at 1, 7, 15, or 30 degrees and a PWM setting which is 8 or 16 KHz.

So, my question, after all that, is how does one know which setting to use. Is it simply a tradeoff of RPM vs current draw? Or is there a better choice for outrunners. I used the 1 degree and got about 300 watts, the 7 degree and 310 watts, then the 15 degree and got 325 watts. But I still do not understand which is "better".

Can anybody shed some light on how this decision is made?

Any help appreciated.

Gene

[scalefreak]

A lot of ESC's today offer the ability to program timing, which is the degrees of advance applied to the motor. Some brushless motors behave differently at different timing settings. 0-8 degrees is normal for low timing and is most efficient on Little Screamers motors along with several of the higher KV motors, including many inrunners. I know AXi's need a Hard or "High" timing advance, as do several high torque/low kv outrunners. The motor is the deciding factor that signals the ESC when to do the frequency switching. A brushless motor is the same as a brushed motor, where the mechanical commutator is replaced with an electronic controller, within the ESC. During operation at all times one of the coils is not activated but a voltage is induced in it by the moving magnets. The controllers senses this voltage and uses it to figure out rotor position and speed. If the frequency isn't programmed correctly in the ESC, it could and probably would have a difficult time controlling the motor throughout the throttle range. Some of you may have noticed that certain setups seem to have a "MUSHY" throttle response from half to full, from idle to half, or all the way through the range of travel. This is usually why.

I would probably go with the 30 degree setting with your motor. You will likely have the most efficiency there and the motor will behave better throughout the throttle range when loaded properly.

Hope this helps!

Chris

[GeneR]

Thank you Chris,

This is just what I was looking for. The motor is headed for a new Eflite Piper Pawnee 15e.

Thanks again!
Gene

[scalefreak]

No problem, Gene. Glad I could help! Message me anytime you wanna' talk electric!


Chris

[mflander]

Good post scale, love your avitar!

Any links to articles pertaining to this subject?

[scalefreak]

This article is about as good as it gets, as far as explaining the basic principles behind what makes a brushless motor tick.

Check it out:

http://www.motioncontrolonline.org/f...sOperation.pdf

[GeneR]

Ok Chris,

Thanks for the article. Of course it intrigued me and now I have a couple of more questions.

So, when the term "sensorless" is applied to a brushless motor it means it has none of the "hall effect devices" and the speed control relies on induced current to know where the rotor is?

And, when it talks about PWM does that imply (in my case the choices were 8 or 16KHz) that is how long the pulse of current is applied to the windings? Or is that the frequency of how often the controller looks at the rotational state of the motor?

Thanks
Gene

[scalefreak]

I'm pretty sure the pulse width modulation (PWM) is constant. Each phase or sine wave is 120 degrees apart and the sine wave alters the width of each pulse. I would say that your second guess is the correct one, however I will put an ESC on the oscilloscope this weekend and post my results. That is a good question that I have not thought about.

[migerthepimp]

i dont quite understand what you just said...
but i have a question about the timing for an axi 4120/14, what would be a good timing for this motor. higer or lower. i would like to get as much power out of it as posible, im putting it in sebart katana 50e(3d)

thanks, miger

	Quote: Originally Posted by scalefreak
	A lot of ESC's today offer the ability to program timing, which is the degrees of advance applied to the motor. Some brushless motors behave differently at different timing settings. 0-8 degrees is normal for low timing and is most efficient on Little Screamers motors along with several of the higher KV motors, including many inrunners. I know AXi's need a Hard or "High" timing advance, as do several high torque/low kv outrunners. The motor is the deciding factor that signals the ESC when to do the frequency switching. A brushless motor is the same as a brushed motor, where the mechanical commutator is replaced with an electronic controller, within the ESC. During operation at all times one of the coils is not activated but a voltage is induced in it by the moving magnets. The controllers senses this voltage and uses it to figure out rotor position and speed. If the frequency isn't programmed correctly in the ESC, it could and probably would have a difficult time controlling the motor throughout the throttle range. Some of you may have noticed that certain setups seem to have a "MUSHY" throttle response from half to full, from idle to half, or all the way through the range of travel. This is usually why. I would probably go with the 30 degree setting with your motor. You will likely have the most efficiency there and the motor will behave better throughout the throttle range when loaded properly. Hope this helps! Chris

[scalefreak]

	Quote: Originally Posted by migerthepimp
	i dont quite understand what you just said... but i have a question about the timing for an axi 4120/14, what would be a good timing for this motor. higer or lower. i would like to get as much power out of it as posible, im putting it in sebart katana 50e(3d) thanks, miger

Definitely higher, I would try between 24-28 degrees for best performance.


Chris

[jeeeeeeright]

I've got an hacker a50-16s and a flighttech synergy 75amp esp, and I'm getting a strange error. When I move the throttle too quickly from low to high the engine makes a strange humming noize and produces no power. In the esc programming I can choose between low-medium-high, and with the settings to low, the error occures in the low range of the throttle stick. If set to medium or high the error occures further and further up.
This is really annoying and kepps me from doing 3d at all, because the engine syddenly can quit if i jerk the throttle too fast, and I have to wait for the motor to slow down a bit before I can gently apply throttle again...
any suggestions here?

[scalefreak]

	Quote: Originally Posted by jeeeeeeright
	I've got an hacker a50-16s and a flighttech synergy 75amp esp, and I'm getting a strange error. When I move the throttle too quickly from low to high the engine makes a strange humming noize and produces no power. In the esc programming I can choose between low-medium-high, and with the settings to low, the error occures in the low range of the throttle stick. If set to medium or high the error occures further and further up. This is really annoying and kepps me from doing 3d at all, because the engine syddenly can quit if i jerk the throttle too fast, and I have to wait for the motor to slow down a bit before I can gently apply throttle again... any suggestions here?

The ESC you have seems to be having a problem with properly timing the motor through the power band, due to not receiving and translating data from the motor fast enough. The ESC has to rely on the motors position to properly time the motor and several esc's aren't up to par with managing the timing needs of a large motor like the A50. The A50 is also an extremely precise motor, as are AXi's, Neus, Scorpions. A Jeti, Kontronik or Castle ESC are all going to be the best match for your motor. Unfortunately, your motor is not going to work well with the ESC you are using. The best timing you can use with the ESC you have is low, which will be ok for hovering but will rob you of power in the long run...also all of your throttle position changes will have to happen slowly in order for the esc to make the timing changes accurately.

Hope this helps