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Old Apr 09, 2006, 09:03 PM
Flying motor mount master
fly_boy99's Avatar
San Jose, California, United States
Joined Oct 2004
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Data
Castle Creation max rpm per pole

I did some digging last nite and could not find the specs for
Castle Creation ESC's:

I believe it's something like:

150000 - 2poles

But I don't know the rest for 4poles, 9 poles and 12poles.

Joe, Bernie, et all please post a response because I think with
a certain motor I've built I'm pushing the rpm limits.

Thanks,
fb
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Old Apr 10, 2006, 06:59 AM
A man with too many toys
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I donít know the exact numbers hut it will spin a NeuMotors 8-pole ORK at 35,000 RPM and a 4-pole at aver 65,000.

Do the math and it comes out about 23,000 for a 12 pole motor.

That information use to be on the CC web site but I canít find it. Does anyone have a link?

.
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Old Apr 10, 2006, 11:03 AM
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How many poles and what kind of rpms are you looking for? I'll let you know if it's possible.
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Old Apr 10, 2006, 01:07 PM
Flying motor mount master
fly_boy99's Avatar
San Jose, California, United States
Joined Oct 2004
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I need to know the max rpm for 12 poles as I think I know my limitation now. I'm looking to break past 30k rpm with a speed APC prop.


is this right?

The max rpm = 2 x frequency x 60/number of poles

150000 - 2poles
75000 - 4 poles
37500 - 8 poles
24000 - 12 poles

Correct me if I'm wrong.
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Old Apr 10, 2006, 02:41 PM
Flying motor mount master
fly_boy99's Avatar
San Jose, California, United States
Joined Oct 2004
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I think I may have found my answer in the CC35 which has some adjustability.

I'd still love an answer from Joe, Bernie, or Shawn.

Thanks guys,
fb
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Old Apr 10, 2006, 04:57 PM
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Fb,

We donít publish the max rpm a CC controller will spin a motor. It is higher than any other available ESC and will spin any motor to destruction.

Bernie
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Old Apr 11, 2006, 01:45 AM
Flying motor mount master
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San Jose, California, United States
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Bernie-

Sent you a PM. Would you kindly respond.

Thanks,
fb
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Old Apr 11, 2006, 06:53 PM
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Old Apr 13, 2006, 06:31 PM
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Old Apr 13, 2006, 06:56 PM
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I've seen the number 190k. Can't remember where though. Must have been in the e-heli-talk.

Have you tried different chopping freqs?
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Old Apr 13, 2006, 07:08 PM
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Old Apr 14, 2006, 10:22 AM
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Quote:
Originally Posted by FRAMEDNLVS
Well I spent the last couple of nights trying to get my prop to spin 2k more then before. I keep rewinding with one less turn on the motor but doesn't seem to get me anywhere. I wonder why?????????????? I wonder why my wasted time seems so unimportant to a vendur (SI.). I'll try a couple to get my results useing different motor part hopeing to get the required rpms I need. Sure would be nice to know if it is the CC-ESC limiting my motor. Wish I knew. Thats ok, I'll just keep winding and unwinding my motors. Maybe I'll try some magnets with a larger airgap, should give me higher rpms. Nope, that didn't work. I'll unwind it again and try something else. Still wonder if I'm limited to how many rpms the CC_ESC can produce. More wire, fewer turns and maybe magnets that aren't as strong could bring the rpms up. Gosh, I'm only at 23 amps and nothing is warm except this darn CC_ESC. I'll unwind it and try multi strand wire with smaller magnets and weaker ones rated for more heat. Darn, last of my two rolls of wire and now the enamel is chipping off the stator from takeing the wire on and off. I'll just have to buy new wire and order a couple of extra stators. Over two weeks into it and wasted about 10 evenings that I could have spent with the family. Still can't seem to bring the rpms up on this motor - CC-ESC combination. Seems like a simple question. What was the answer, "It is higher than any other available ESC". I was told by the other manufacturer that his ESC is rated up to 160k electrical rpms, (2) magnets make one electrical rpm. So I have to assume the CC-ESC should be able to do 160,000+min of 1 more to exceed other manufacturers. I can except that. Lets see, what was the other part of that "and will spin any motor to destruction". Any motor to destruction. This is where I need some help. I know my bearings are rated for 60K. I wonder what the other limitations of my motor would be? Pretty solid one piece steel can on the one cheap motor that I have. I would think that would not distort or have any problems going 60K. Just what are the limits of any motor to spin to destruction? "ANY MOTOR", that leaves it wide open and very general. I wonder if there is a better way to phrase this question so Fly_boy and others would feel like they haven't wasted there time and money trying to obtain a simple goal.

Whatever,
Chirs

Wow -- well removing windings often wont increase RPM at all if you are near the ouput limits of the motor anyway. You just keep reducing efficiency. Your controller is probably getting hot because you are saturating the back iron, and are already at the maximum output of the motor. There is a point on the efficiency curve of every motor where efficiency drops so rapidly that you can continue to dump more and more power into a motor, and output DOES NOT INCREASE. I doubt you are getting anywhere even close to the limits of the controller... but since you haven't decided to give any information about your motor and setup, I'm forced to guess. 160,000 electrical RPM is 80,000 RPM on a four pole, 40,000 RPM on an eight pole, 20,000 RPM on a 16 pole. Are you saying you are beyond those kinds of RPMS? If you aren't THEN THE ANSWER IS "NO". The controller is NOT limiting the RPM of your motor -- your MOTOR is limiting the RPM.

We aren't positive of the maximum -- because we don't artificially limit the RPM output of the controller. The reason is that there is some variation in maximum RPM due to differences in back-emf signal from motor to motor. So the maximum commutation RPM depends on the motor.

There is a practical limit imposed by the ESC -- and that is because there is some overhead involved with processing in the commutation code. It also takes a finite amount of time to turn the FETs on and off -- and that can vary somewhat from controller to controller. However, because that can change based on the TYPE AND DESIGN of the motor being run, there isn't a good/fast answer.

160,000 on a two pole was suggested -- and for most controllers that's a pretty good answer. At 160,000, timing is still accurate, and the ESC doesn't have any issues with FET turnon/turnoff times (except for the Phx-10, which has slower high-sides.) At about 250,000, overhead in software becomes an issue, and timing is near neutral (when set for default timing.) At about 350,000 timing will be retarded by around 12 degrees, and from that point on no increase in RPM will be seen because the controller will limit motor RPM by continuing to retard the timing (due to processing overhead.) However, by that time the hardware on most controllers probably won't be able to keep up with commutation rates anyway. And again, that will vary from controller to controller based on the design and hardware on that particular controller.

So you see, there is no correct answer. And 160,000 is a good, safe, practical limit to work with.

Therefore, bashing us for not giving an answer is silly.

Patrick
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Old Apr 14, 2006, 12:05 PM
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Old Apr 14, 2006, 01:06 PM
Flying motor mount master
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San Jose, California, United States
Joined Oct 2004
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Patrick-

I have a speed motor which on 3S pushes a CC-25 and CC-35 to 24k no problem. After a static bench run of say 45 seconds the motor is only 100 degree F. This leads me to believe that I can try for a 4S and see if I can get more out of the motor.

I may be completely wrong and heat has nothing to do with saturating the iron but I believe its a byproduct and would show up.

2 pole - 160000
4 pole - 80000
8 pole - 40000
16 pole - 20000

I believe the above numbers are correct and it's kinda ironic that my motor cannot break through the 25k barrier. I guess I'll have to build a comparable motor with 6 magnet poles and let you see how it can pass this one up to 60k rpm. Amp draw is a serious consideration though.
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Old Apr 14, 2006, 02:35 PM
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Quote:
Originally Posted by FRAMEDNLVS
Patrick,
Thank you for your reply. I didnít mean to bash, I just wanted you and CC reps to realize this is a true concern for me as a motor hacker and cdrom kit builder. I find 160k is going to be a big problem on my motor that I'm working on. Specific numbers for me (not limited to just this example) are 10 magnet poles:
Battery Efficiency: 100%
Max Current: 13.60 A
Avg Current: 13.30 A
Max Voltage: 10.97 V
Avg Voltage: 10.86 V
Min Voltage: 10.77 V
Max Power: 149.23 W
Avg Power: 144.24 W
Max Tach: 28396 RPM
Avg Tach: 27285 RPM

The motor has been pushed with a larger prop beyond 200w with 16 magnet pole but not turning much over 24k. I have been running this with the CC-35 that is quite old and have to set it for the higher switching frequency to get it to run at high rpms. With the above mentioned motor I was able to run it the same with CR esc with a slight decrease in rpms and amps. I really would like to push my motor with 14 magnet poles over 35k.

I understand you can't give me an exact answer to what are the rpm limits of your controllers. I really do appreciate your time and apologize for the rant.

At this point maybe you could help with my problem and suggest some things that might help me achieve my objective of getting the high rpms.

I also want to mention that I had planed on going down to a 3" prop and trying for even higher rpms.


Thanks,
Chris

Well, to be quite honest with you, high pole counts and high RPM don't really belong together... the reason is that as you increase commutation rates the efficiency of the motor drops dramatically... This is because you are increasing the rate at which the magnetic field orientation and strength change across the iron in the stator. This is not ideal, as iron losses are proportional to frequency squared... In other words, your iron losses will become a HUGE factor, and will be the main issue with getting good efficiency out of the motor.

Also remember that there is a maximum rate at which the current flow and direction can be changed given a constant voltage source -- this is the inductance of the motor coming into play. This can be compensated for (somewhat) by increasing the timing advance (which the controller does automatically) -- however as commutation rates increase near the maximum the controller can deal with, the amount of timing advance available to the controller also decreases (becuase it takes a finite amount of time to commutate and setup variables for the next commutation cycle.)

If you are looking for high RPM/ low torque -- a lower pole count motor will really get you where you want to go with MUCH better efficiency than a high pole count motor. First, because the commutation rates are much lower, so iron losses are lower, secondly because inductance is usually lower on non-outrunners, and because the controller will be better able to accurately handle the timing advance, because it has enough available time to calculate correct timing advance.

Another possibility would be to go to a "ironless" or low iron (like slotless) motor design. Or, alternately, go to a better material than iron for the stator (Iron is very poor at high frequencies--) like a nickle or cobalt material.

Hope this helps!

Patrick
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