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simibill
07-23-2007, 10:20 PM
How does one go about determining how many poles there are in a brushless outrunner motor?

pilotpete2
07-24-2007, 01:43 AM
You usually can see the poles well enough through the cooling holes on the front of the motor with an outrunner, then just count em':), inrunners , now they ain't as easy.:< manufacturers specs will probably give that info.
Pete

Larry3215
09-12-2007, 07:35 PM
Usually when someone is refering to the number of "poles" in a motor its the number of 'magnetic' poles they are talking about - NOT the number of stator teeth.

In an outrunner you can usually just count the number of magnets and thats the number of "poles".

However, that doesnt always work because some outrunners can have, for example, a 4 pole setup with the magnets arainged in a NNSSNNSS patern. Thats 8 magnets but only 4 magnetic "poles".

Outrunners will always have a different number of stator teeth than magnets, but the ratio varies depending on how its setup.

Inrunners are almost impossible to determine on your own as the central magnetic rotor is usually hidden and made/molded into one piece and the number of magnetic poles is often not obvious to the naked eye.

Larry

Bill G
09-13-2007, 05:20 AM
Inrunners are almost impossible to determine on your own as the central magnetic rotor is usually hidden and made/molded into one piece and the number of magnetic poles is often not obvious to the naked eye.

Larry
You know when the split the rotor in half through the plane where the fields oppose each other.:D That's 2 poles.

Larry3215
09-13-2007, 06:51 AM
Yup - that is a good (if a little late) indicator for sure :)

Larry

P.S. I wonder if I should list why I was banned from RCG? ;)

ron_van_sommeren
09-13-2007, 03:27 PM
... Outrunners will always have a different number of stator teeth than magnets ... Inrunners ditto.

B.L.E.
09-18-2007, 01:55 AM
Find an old fashioned analog voltmeter and count the number of times the needle swings back and forth when measuring the generated voltage while turning the motor by hand.
One swing per revolution (a plus and minus cycle) = a two pole motor
Two swings per revolution = a 4 pole motor
Three swings = a six pole motor
And so forth.

I have used this technique often to find out the pole count of mystery 3 phase motors that have obliterated nameplates.

simibill
09-18-2007, 02:46 AM
Great idea, thanks.

Bill G
09-20-2007, 05:59 AM
http://www.wattflyer.com/forums/images/icons/icon1.gif How many Poles?
.....does it take to....? :D

You know this thread, given its title, would proabably fit well in the humor forum too. Ok, that was bad, I know.:eek:

Happy Days
12-28-2007, 03:30 AM
Talking of Poles, does anyone know what defines a 'High' or 'Low' pole count motor?

B.L.E.
01-07-2008, 01:29 PM
Talking of Poles, does anyone know what defines a 'High' or 'Low' pole count motor?

I think that outrunners usually have high pole counts, 12 to 16. Inrunners usually have low pole counts, as little a 2, (the fewest poles a motor can have).
There's no reason an outrunner can't have only two poles, in fact if you take a two pole speed 400 brushed motor and made the armature stationary with a brushless esc connected to the three commutator segments and allowed the case to turn around the stationary armature, you have a two pole outrunner. It probably won't be any more efficient that way than it was as a brushed motor however. It still has ferrite magnets.

Dr Kiwi
01-07-2008, 07:32 PM
Another quirk [no change in the stator windings] is to double the number of magnets to get lower Kv.

Justgofly produces 6-magnet outrunners of about 3000Kv, but if you use a bell with 12-magnets the Kv is around 1700.

Happy Days
01-08-2008, 02:29 PM
Right!.................... thanks guys. I needed to know so as to programme my Synergy ESC. It just invites a setting for High or Low pole count motors.

Well, you learn something every day!

DarZeelon
01-17-2008, 08:53 AM
Usually when someone is referring to the number of "poles" in a motor its the number of 'magnetic' poles they are talking about - NOT the number of stator teeth.

In an outrunner you can usually just count the number of magnets and thats the number of "poles".


I would say this is incorrect, Larry.

I have several outrunner motors here, most of which are defined by their manufacturer as 12 pole motors. They all have 12 wire-wound electromagnetic poles (stator teeth?) and 14 neodymium magnetic poles.

The other smaller, inexpensive motor from another manufacturer is not categorized by the number of its poles, but has 9 wire-wound electromagnetic poles and 12 magnetic poles.

The number of wire-wound electromagnetic poles must always divide evenly by 3, to allow the same number poles to always be energized by the 3 phases. The electromagnetic poles that are energized at any one time must be spread evenly around the stator, or the motor would run like... well... one of those 'odd-firing' Buick V6 engines of the early '80s...

The number of magnetic poles must always be an even number, to have the N-S-N-S-... sequence all around, with no adjacent N-N, or S-S (or N-N-N-N or S-S-S-S in case of paired-combo poles) anywhere.
...Which would result in an even worse case of the last few words of the previous paragraph...

If the same number of magnetic and electro-magnetic poles are used, the rotor would just be held static...:blah:

ron_van_sommeren
01-17-2008, 05:55 PM
A magnetic pole can consist of more than one magnet to create a bigger one. Some manufacturers do this.

B.L.E.
01-17-2008, 06:29 PM
I would say this is incorrect, Larry.

I have several outrunner motors here, most of which are defined by their manufacturer as 12 pole motors. They all have 12 wire-wound electromagnetic poles (stator teeth?) and 14 neodymium magnetic poles.

The other smaller, inexpensive motor from another manufacturer is not categorized by the number of its poles, but has 9 wire-wound electromagnetic poles and 12 magnetic poles.

The number of wire-wound electromagnetic poles must always divide evenly by 3, to allow the same number poles to always be energized by the 3 phases. The electromagnetic poles that are energized at any one time must be spread evenly around the stator, or the motor would run like... well... one of those 'odd-firing' Buick V6 engines of the early '80s...

The number of magnetic poles must always be an even number, to have the N-S-N-S-... sequence all around, with no adjacent N-N, or S-S (or N-N-N-N or S-S-S-S in case of paired-combo poles) anywhere.
...Which would result in an even worse case of the last few words of the previous paragraph...

If the same number of magnetic and electro-magnetic poles are used, the rotor would just be held static...:blah:




The number of teeth of a stator is not the number of magnetic poles the stator has. If you put some D.C. current through the stator winding and counted the number of magnetic poles with a small compass, you will find that the magnetic field generated by that DC current has the same number of poles as the field magnets do.

The coils can also span more than one tooth, in fact with larger motors that is the rule. In this particular 3 phase stator, the stator has 108 teeth or slots and each coil spans 14 teeth. Six adjacent coils are connected in series to make a group that generates one magnetic pole. This is a 6 pole motor that turns 1200 rpm on 60 Hz current.

http://i170.photobucket.com/albums/u260/ben_eberle/IMG_0959.jpg

DarZeelon
01-17-2008, 08:22 PM
B.L.E.,


But on a typical brushless outrunner motor used, with 12 electromagnetic 'stator teeth', these poles are not grouped, but rather wound in series as follows; 1-4-7-10 on coil I, 2-5-8-11 on coil II and 3-6-9-12 on coil III.

Cheers

ron_van_sommeren
01-17-2008, 10:29 PM
For a controller, you need to know the number of magnetpoles.

Larry3215
01-17-2008, 11:01 PM
My statement was correct as far as it went :)

When programing controllers or things like rpm sensors on the Eagle Tree logger for example, you need the number of magnetic poles - NOT the number of stator teeth.

Also - I did say you can usually get that number by counting the number of magnets. As Ron pointed out, some motors are built with NNSSNNSSNNSS araingements. You might have 12 magnets making up a 6 pole motor.

Larry

Larry3215
01-17-2008, 11:06 PM
I would say this is incorrect, Larry.

I have several outrunner motors here, most of which are defined by their manufacturer as 12 pole motors. They all have 12 wire-wound electromagnetic poles (stator teeth?) and 14 neodymium magnetic poles.

.........:blah:





Who makes those motors?


Id guess they are some of the chinese knockoffs? Those guys often have no clue about thier own motors. More often than not they have completely wrong Kv, Io etc, numbers of windings vary from tooth to tooth, magnets are set wrong etc.

From what I have seen in my testing, most all the specs are invented rather than measured :)

Larry

ron_van_sommeren
01-17-2008, 11:09 PM
Almost all manufacturers produce dLRK motors Larry. Or am I misunderstanding your question?

Larry3215
01-17-2008, 11:36 PM
Almost all manufacturers produce dLRK motors Larry. Or am I misunderstanding your question?

Sorry Ron.

I meant the spicific ones he has where they are calling the number of stator poles the number of magnetic poles.

Larry

ron_van_sommeren
01-17-2008, 11:42 PM
That's way I always write teeth/slots/statorpoles versus magnetpoles.

ron_van_sommeren
01-17-2008, 11:50 PM
A magnetic pole can consist of more than one magnet to create a bigger one. Some manufacturers do this.E.g. www.flyware.de
(http://www.flyware.de)


http://www.flyware.de/wde/shop-produktinfo/torquerex40/T-REX-40.gif

DarZeelon
01-18-2008, 07:33 AM
Who makes those motors?


Id guess they are some of the Chinese knockoffs?



Larry,


They are KD. Indeed a Chinese knock-off...

BUT...

...One of these specific motors, the A50-14L, which is reputedly an Axi 4130/16 equivalent, uses an actual 1,700 Watts, 61.7A on 8 cells, spinning a 16x12 APC...

This is ~20% more than that Axi (tested back-to-back) and also 200 Watts more than the Hacker A50-14L (the same signification)...

It really surprised people here since it is such a bargain.

simibill
01-18-2008, 12:41 PM
Larry,


They are KD. Indeed a Chinese knock-off...

BUT...

...One of these specific motors, the A50-14L, which is reputedly an Axi 4130/16 equivalent, uses an actual 1,700 Watts, 61.7A on 8 cells, spinning a 16x12 APC...

This is ~20% more than that Axi (tested back-to-back) and also 200 Watts more than the Hacker A50-14L (the same signification)...

It really surprised people here since it is such a bargain.



Where do I find the KD motors you are speaking of?

DarZeelon
01-18-2008, 01:12 PM
I sent you an E-mail. Bill.

Cheers.

Larry3215
01-19-2008, 05:38 AM
Larry,


They are KD. Indeed a Chinese knock-off...

BUT...

...One of these specific motors, the A50-14L, which is reputedly an Axi 4130/16 equivalent, uses an actual 1,700 Watts, 61.7A on 8 cells, spinning a 16x12 APC...

This is ~20% more than that Axi (tested back-to-back) and also 200 Watts more than the Hacker A50-14L (the same signification)...

It really surprised people here since it is such a bargain.



DarZeelon,

If a motor draws more power on a given prop, that does not automatically mean is a more powerfull motor. You must also compare the RPM its turning on exactly the same prop.

A less efficient motor will always draw more power than a more efficient motor on the same load (prop) - but if it is turning that prop at the same or lower RPM then its a loosing proposition :)

Even if its turning it faster - it needs to be turning enough faster to justify the extra power used.

Putting watts into heating air instead of moving air is a poor use of amps :)

Give us some relative rpm readings using the same prop and I can tell you which motors is more efficient.

Larry

DarZeelon
01-19-2008, 06:48 AM
DarZeelon,

If a motor draws more power on a given prop, that does not automatically mean is a more powerfull motor. You must also compare the RPM its turning on exactly the same prop.

A less efficient motor will always draw more power than a more efficient motor on the same load (prop) - but if it is turning that prop at the same or lower RPM then its a loosing proposition :)

Even if its turning it faster - it needs to be turning enough faster to justify the extra power used.

Putting watts into heating air instead of moving air is a poor use of amps :)

Give us some relative rpm readings using the same prop and I can tell you which motors is more efficient.

Larry

You are correct, Larry.


In this test we did not actually compare the RPM, just listened and it sounded more powerful...

But had there been a very diminished level of efficiency, the motor would have become much hotter...
This KD motor could be 'fisted' immediately following the flight. It was not hotter than the Axi was.

Cheers.

Larry3215
01-19-2008, 07:11 AM
Get some rpm numbers on the same exact prop along with volts and amps and then you canmake a good comparison.

Another thing to keep in mind is that even small differences in the Kv of the motors will cause significant differences in the amp draw. the higher Kv motor will draw morwe current as it trys to spin the prop faster.

Its important to have all the relavant data when making comparisons.

Weight is a factor as well.

By the way - Im not knocking the KD motors - dont have enough data to do that :)

Larry

DarZeelon
01-19-2008, 07:18 AM
Larry,


I still don't have a model for this motor, so this test was done with the favor of the Axi owner (the KD motor is a 3 minute, drop-in replacement for it in his plane).

...Even the Watt meter and the prop were his...

When I have an update, I'll sure post it.

The weight and the appearance of these two motors is the same, BTW.

Cheers.

Bill G
03-28-2008, 12:55 AM
How many Poles?

Simibill I opened this thread up and was expecting to see a good joke.:D

Bill

Dr Kiwi
03-29-2008, 07:32 PM
Since you seem desperate for one, Bill:

<center>A Polish man was walking down the street ...

</center>A Polish man was walking down the street, carrying a brown paper bag. He ran into one of his friends, who asked, "Hey! What do you have in the bag?"
The man tells his friend that he has some fish in the bag.
His friend says, "Well, I'll make you a bet. If I can guess how many fish you have in the bag, you'll have to give me one."

The man says, "I'll tell you what. If you tell me how many fish I have in this bag, I'll give you both of them."

ron_van_sommeren
03-29-2008, 09:50 PM
...
But on a typical brushless outrunner motor used, with 12 electromagnetic 'stator teeth', these poles are not grouped... www.actro.de outrunners, years before outrunners became popular, in fact, the first ones.

http://www.actro.de/bilder/gross/actroSchnittmodell.gif

DarZeelon
03-30-2008, 01:06 AM
Well, Ron,


This specific brushless motor does seem to have grouped stator-teeth...

They are grouped diffferently from what I had initially envisioned.
I thought of each 'tooth' being a member of one windings group...

Here, each stator tooth is a member of all three windings groups, depending on which is currently energized and what its polarity is...


Cheers,

Dar

ron_van_sommeren
03-30-2008, 10:35 PM
It's the only winding of this type I've seen in 'our' RC e-flightmotors, and these Actro (excellent quality) motors have been around for at least ten years.

DarZeelon
03-31-2008, 06:28 AM
Ron,


I will need to take apart a few more brushless motors to be sure...

It does make sense that all applicable 'teeth' be energized, at any time.
I.e. if a stator tooth can pull an adjacent magnetic pole in the right direction, it must be powered to do so.