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Mixalis
09-28-2012, 03:48 PM
Hello to all members!
First of all it's nice to join this community and share knowledge but i admitt that mine is limited!!!

Well i have a problem with a brushless outrunner motor which got burned and after gathering many info especially from you all i tried to rewind it.
The motor is a Freewing (2226-1250kv) which came with the Hobbyking Kinetic 800.The motor has 12 magnets and 9 teeth.
The initial wind was a 9.5-10 turns of 5 strands #32 AWG.
According to the wire calculator from http://www.bavaria-direct.co.za/models/motor_info.htm
i used 8 turns of one strand #24 AWG.
After many tries cause it was my first rewind of a motor i managed to have a neat wind with no short circuits.
I connected it to a 30Amp ESC and a 3cell lipo and it shuttered a little at, lets say 10% of throttle but with more power it turned like hell with no problem.It was obvious that the rpms had icreased a lot!
But when i mounted the 8x5 folding prop it could not start at all.It shuttered and got hot.
So i then used a one strand 20 turns #28 wire to increase torque and decrease rpms but now it still shutters when i gently increase throttle and again it can not start at all when i mount the prop???

I do not know what to do:confused:

JetPlaneFlyer
09-28-2012, 04:43 PM
Sounds like you have got the winding pattern wrong and/or have connected the tails up in the wrong way.

Assuming that the ESC is ok.. If it was connected to the motor when you burned it out then the ESC may have been damaged too.

ron_van_sommeren
09-28-2012, 06:25 PM
Why/how did your original motor burn?
Are the magnets still ok? I.e. no magnetic strength lost due to high termperatures? The weakening would be permanent.
Weaker magnets will give a higher Kv and lower Kt (torque per ampère). This results in higher motorcurrent -> higher Kv -> higher current -> higher temperature -> weaker magnets -> higher Kv -> higher current -> higher temperature -> weaker magnets -> higher Kv -> higher current -> higher temperature -> weaker magnets ...
What winding diagram did you use?
How did you hook up the three phases, in star or delta? What was the original hookup?
Begin end ending of the wires matters a great deal, you cannot just connect one phase to the other. In star you connect all starts or all ends. In delta you connect ends to starts. Do it wrong and you'll get phase differences of e.g. 0°, 240°, 300° instead of the correct 0°, 120°, 240°
Check out my signature.

More pictures
SPEEDY-BL self made brushless controller (http://www.aerodesign.de/peter/2001/LRK350/SPEEDY-BL_eng.html)


120° difference in phase (the 'grass' is PWM chopping (https://en.wikipedia.org/wiki/Pulse-width_modulation) for speed control)

http://www.aerodesign.de/peter/2001/LRK350/Speedy-BL/Teillast_Motor.gif

Mixalis
09-29-2012, 10:24 AM
I believe that my winding pattern and end connection is right!
The original hookup was in star connection and i did the same.
My winding diagram is from http://www.bavaria-direct.co.za/models/motor_info.htm
(Star (Wye) Connection)
I had mounted the motor to a not so good, due to overweight, DLG that i build and i believe it was burn due to insufficient air for cooling.
I am not sure if the magnets are damaged???

Mixalis
09-29-2012, 11:33 AM
Some pics might help!

flydiver
09-29-2012, 04:44 PM
You can claim anything you want but a stuttering motor is a clear indication of something not right. You wound wrong, terminated improperly, did not do a good job soldering leads (cleaning off insulation), or you created a short. It's got to be one of those things. Sorting out your first few motors can be a problem. I strongly recommend people NOT start with an 'advanced and burned out' motor as it just adds additional layers of complexity to an already frustrating task.
What wire did you use?

Magnets need to get pretty hot to de-magnetize. It's possible but I think it's more likely one of the above problems.

ron_van_sommeren
09-30-2012, 04:45 PM
.. My winding diagram is from http://www.bavaria-direct.co.za/models/motor_info.htm ...
Several winding diagrams on Christo's page there. Which one are you referring to?

Magnet placement is pretty poor, more cogging, more noise.

Did you remove wire insulation (lacquer) before soldering?

Check out the checks and tests in
http://www.rcgroups.com/forums/showthread.php?t=240993

Do the power-drill test. What three voltage levels do/did you measure?

Mixalis
10-01-2012, 03:10 PM
I used #28 KEMO wire and i did Star (Wye) Connection
The power drill test gave me 0.3V in all three phases at aproximately 1500rpms.
I will check my soldered leads once again!!

flydiver
10-01-2012, 03:45 PM
I used #28 KEMO

Not familiar with that wire-not USA.
We have an electronics company in the US called Radio Shack that sells a bunch of electronics. They have wire. Their wire is terrible. It's very easy to get shorts with it. So, I'm not saying it is your wire, but shorts are one of the more common problems for ALL winders and new winders in particular.
Since you were using a use and abused (burned out) stator the chances of roughness on the edges is higher which increases the possibility of shorts. There are entire threads trying to deal with bad stators and recover them or touch up bad spots.

Good wire and a clean stator make winding life a lot easier. I won't even work with really bad stators anymore-not worth the frustration for me.

kyleservicetech
10-01-2012, 06:26 PM
Hello to all members!
First of all it's nice to join this community and share knowledge but i admitt that mine is limited!!!

Well i have a problem with a brushless outrunner motor which got burned and after gathering many info especially from you all i tried to rewind it.
The motor is a Freewing (2226-1250kv) which came with the Hobbyking Kinetic 800.The motor has 12 magnets and 9 teeth.
The initial wind was a 9.5-10 turns of 5 strands #32 AWG.
According to the wire calculator from http://www.bavaria-direct.co.za/models/motor_info.htm
i used 8 turns of one strand #24 AWG.
After many tries cause it was my first rewind of a motor i managed to have a neat wind with no short circuits.
I connected it to a 30Amp ESC and a 3cell lipo and it shuttered a little at, lets say 10% of throttle but with more power it turned like hell with no problem.It was obvious that the rpms had icreased a lot!
But when i mounted the 8x5 folding prop it could not start at all.It shuttered and got hot.
So i then used a one strand 20 turns #28 wire to increase torque and decrease rpms but now it still shutters when i gently increase throttle and again it can not start at all when i mount the prop???

I do not know what to do:confused:

If you've got one winding reversed, it can cause all sorts of problems. I've done it.

If one winding is reversed, this thread will show it.
http://www.wattflyer.com/forums/showthread.php?t=35216

The test in this thread that will show a reversed winding is the one where the motor is spun up with a battery operated drill with all motor wires directly shorted to each other. If the torque "Chuggs", you might have a reversed winding. Only other way to find it is with an oscilloscope.

If you've got a winding reversed, just reverse connect that windings
leadwires, no need to rewind the motor.

ron_van_sommeren
10-02-2012, 06:59 PM
I used #28 KEMO wire and i did Star (Wye) Connection ...That is the hook up of the three wires, in star and delta are the two possible hook-ups of the wires after winding. Star and delta are not winding diagrams.

You probably used ABCABCABC, as in the picture belwo According to the voltages you measured, you don't have shorts, nor do you have wound one or more coils, in the wrong direction, nor did you hook up the wires wrong.

Several excellent articles on building lrk and cd-rom motors, pictures, winding diagrams, by Brian Mulder a.k.a. 'Mr DIY' on E-zone:
www.southernsoaringclub.org.za
-> Articles from Southeasters
-> Electric Motors - part 1 ... part 5

http://www.bavaria-direct.co.za/models/images/CD_Star_diagram.gif

Mixalis
10-03-2012, 03:30 PM
You probably used ABCABCABC, as in the picture belwo According to the voltages you measured, you don't have shorts, nor do you have wound one or more coils, in the wrong direction, nor did you hook up the wires wrong.


Yes that is my winding patern.
I do not see any other explanation for my problem other than my ESC.But i do no have a spare one to check.

Mixalis
10-11-2012, 03:34 PM
I am about to change the magnets of my motor to see if it changes something thus the original placement is of poor constuction (see photo post #5)
My problem is that i can not find neodymium magnets of 13x5x1mm size as the original.
I even checked at http://www.supermagnete.de/eng/ and i can only find10x5x1mm.
Will it be sufficient for the motor??

My second question is that if we know the Kv, the number of windings and thickness of the wire can we accumulate how to make different Kv motor?
For example we have a 2000Kv motor of 10 turns of #28 wire, can we make it 1000Kv be removing for example 5 turns of wire??

kyleservicetech
10-11-2012, 05:11 PM
I am about to change the magnets of my motor to see if it changes something thus the original placement is of poor constuction (see photo post #5)
My problem is that i can not find neodymium magnets of 13x5x1mm size as the original.
I even checked at http://www.supermagnete.de/eng/ and i can only find10x5x1mm.
Will it be sufficient for the motor??

My second question is that if we know the Kv, the number of windings and thickness of the wire can we accumulate how to make different Kv motor?
For example we have a 2000Kv motor of 10 turns of #28 wire, can we make it 1000Kv be removing for example 5 turns of wire??

Another source for magnets:
http://www.kjmagnetics.com/products.asp?cat=11

FYI, the physical size of these magnets is critical, the clearances between the magnets and the stator inside these motors is very small. To small, the magnets will hit the stator. To large, you loose power.

I've done this with the www.gobrushless.com (http://www.gobrushless.com) motors. Found the best way to install the magnets is to place the magnets, and hit them with thin CA. Then, bridge between the magnets with plain old baking soda, making certain the baking soda does not rise above the magnet level. Then place a drop or three of thin CA on the baking soda. Instant concrete! And this stuff is pretty much heat proof.

If you've not done this before, it's a lot of work. Beginning with the fact that while placing the magnets, they tend to move around due to very substantial magnetic forces between them. You need a non metalic fixture to hold them in place while gluing them.

I've got a few of these magnets from work 1.5 by 3 by .375 inches. Got to really be careful with magnets this size. I got a finger smashed between two of them a few years ago. It didn't stop bleeding for 9 hours.

Mixalis
10-12-2012, 03:03 PM
Thanks for the tips!!!

Is there an equation of how to achieve a speciffic Kv when winding a motor?

kyleservicetech
10-12-2012, 05:18 PM
Thanks for the tips!!!

Is there an equation of how to achieve a speciffic Kv when winding a motor?

Nope, that would get into serious magnetics formulas, including airgaps, type of steel, quality of steel, turns and likely a lot of other stuff. Way over my head. :oops:

What I've done is wind up a motor with real small diameter, easy to work with magnet wire. Then run up the motor at no load and see what RPM it turns. Since the number of turns on the motor windings is related to the motor RPM, you can use the number of turns to indicate what diameter wire will be required for the RPM you need.

As an example, a 15 turn motor will turn over exactly twice as fast as a 30 turn motor. Then you've got to figure out what size wire will fit into the motor stator and completely fill up the wire slot.

Yeah, that requires a supply of different wire sizes. Before retiring, I did have access to a whole range of wire sizes. That stuff came in 50 and 100 and 250 pound spools, so I'd get my wire from the end of the spool after the shop wound their coils. There was always a few dozen or few hundred feet left after a series of coils were wound from those spools. Those wire sizes varied from about #34 to three inch wide copper strips that could carry 500 Amps or more.

Mixalis
10-13-2012, 02:33 PM
Thanks!
This empirical equation i was looking for!
It is a nice way to find out what winding you should do to manufacture a desired motor!!!

ron_van_sommeren
10-14-2012, 11:23 AM
I am about to change the magnets of my motor ...Magnets (or magnetpoles) must be installed alternating(ly?)
N-S-N-S-N- ... etc
or
NN-SS-NN-SS-NN- ... etc. (tiled/cascaded magnetpoles)
Check it with a spare magnet: attract-repel-attract-repel-attract- ... etc

Instructions/pictures
http://www.torcman.de/index_e.htm
-> downloads
-> Assembly Procedure TM280, 350, 430
-> Chapter 3: Glueing rotor and magnets

The UHU-Plus Endfest 300 mentioned there is a good quality epoxy 2-component glue

... to see if it changes something thus the original placement is of poor constuction (see photo post #5) ...The magnet misalignment is not the cause of your problem. Better alignment will reduce cogging. Nevertheless, installing stronger magnets is a good option, it will lower Kv. To get your original Kv you can use less winds (less copper resistance) of thicker wire (again, less copper resistance). Stronger magnets will give you higher efficiency. I'm ignoring magnetic saturation here and stronger magnets have lower Curie-temperature! (https://en.wikipedia.org/wiki/Curie_temperature).
See also
http://www.supermagnete.nl/eng/faqs
-> N40, N42

Efficiency governs power/weight ratio
Higher efficiency does not only mean that the motor makes better use of the batteries' power, it also means the motor is able to handle a higher power input before hitting its maximum temperature mark i.e. a the power/weight ratio will be higher.

An example
Say the motor has an efficiency of 70% and it can handle 50Watt input. That means it can get rid off 30%*50=15Watt excess heat. Now, by cramming in thicker wire (and/or using better stator-iron, segmented magnets), efficiency increases to say 75% (I'm a bit optimistic here). The motor's ability to loose those 15Watts has not changed (by radiation, convection and conduction). This means the motor now can handle 60Watt before it hits the 15Watt (25%*60Watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20% (from 50Watt to 60Watt). That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

B.T.W. where do you live? I take it somewhere in Europe?

kyleservicetech
10-14-2012, 07:37 PM
That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

B.T.W. where do you live? I take it somewhere in Europe?

That's why I like those motors that state their winding resistance such as the Hackers and similar types. Winding resistance plays a substantial part in motor efficiency, and it is so easily measured. All it takes is a pair of digital multimeters, a power resistor and a battery.

Take a look:
http://www.wattflyer.com/forums/showthread.php?t=50740

Mixalis
10-15-2012, 03:02 PM
The magnet misalignment is not the cause of your problem. Better alignment will reduce cogging. Nevertheless, installing stronger magnets is a good option, it will lower Kv. To get your original Kv you can use less winds (less copper resistance) of thicker wire (again, less copper resistance). Stronger magnets will give you higher efficiency. I'm ignoring magnetic saturation here and stronger magnets have lower Curie-temperature! (https://en.wikipedia.org/wiki/Curie_temperature).

Excellent informations!I just keep reading all the nice articles.Thank you guys.

I did not change the magnets.I just reglued them in better position hopping for something that did not happen as you said.It just limited the cogging,did not disappear it.
I think i have to find better-stronger magnets and replace the winding again!Then we will see.


B.T.W. where do you live? I take it somewhere in Europe?

I am Greek:)

kyleservicetech
10-15-2012, 05:19 PM
Magnets (or magnetpoles) must be installed alternating(ly?)
. I'm ignoring magnetic saturation here and stronger magnets have lower ?

If my old memory is correct, magnetic saturation is one limit to the maximum current any motor can pull at any given RPM. Once the magnetic steel paths hit magnetic saturation, the motor efficiency plummets, and everything gets hot. Heavier steel structure adds weight, and is partly the reason those motors that claim 200 watts or more per ounce of motor weight might be exaggerating a little bit.

ron_van_sommeren
10-15-2012, 09:16 PM
... I am Greek:)I compiled a list of RC flight fora worldwide (http://www.modelbouwforum.nl/forums/de-modelbouwkroeg/135271-vakantie-vragen-overzicht-niet-nl-modelbouw-fora.html), but the Greek fora are still missing. Can you help me here, do you know of Greek fora?

Mixalis
10-15-2012, 09:30 PM
I see that you mean Greek forum!I know two with many members and daily posts.
http://aeromodelling.gr
http://www.aeromodelistis.com

Mixalis
10-27-2012, 06:58 PM
Generally speaking the N35 neodymium magnets would benefit my motor or i need a stronger magnet say N48-50??

ron_van_sommeren
10-28-2012, 04:44 PM
Stronger magnets will give you lower Kv, but may cause magnetic saturation and they have lower Curie temperature (https://en.wikipedia.org/wiki/Curie_temperature). If you have N35 magnets lying around just go ahead and use them.

CarpenterDave
03-24-2013, 11:04 PM
For an ABC wind-ing you did get 7 stator teeth out of 9-----try again-::o:sad::{:(:mad::silly::ws:
167354

kyleservicetech
06-06-2013, 06:17 PM
That is the connect of the three cables, in celebrity and delta are the two possible hook-ups of the cables after twisting. Star and delta are not twisting blueprints.

Here is some useful information on winding brushless motors.
http://www.bavaria-direct.co.za/models/motor_info.htm

I've wound a half dozen of these www.gobrushless.com motors, they work well. Only problem, winding your own motor now days is more expensive than just buying one ready to use. :( :eek: :cool: