# 16-pole controller...



## modern_messiah (Dec 8, 2010)

I all,

Quick question because I am _very_ new to this and am doing some research before I bite off more than I can chew.

I am looking at building my own 3-phase Axial Flux Core-less motor. The current design incorporates 15 teeth and 16 pole-pairs. In another thread it was stated (where I listed 10 poles as an example): 


> The Curtis AC controllers for an example will only handle 300Hz, meaning 18 000 electric rpm. Since you have 10 pole pairs, this controller would limit you to only 1800 motor rpm.


The poster went on to explain that Kelly controllers can provide up to 100,000 electric rpm. With 16 poles the motor could run a shade above 6000rpm. Still not fantastic but then again I have no idea about what sort of performance I am looking at currently - it's all still theoretical.

But as you can see I need to know more about what sort of controllers are out there and if any will would be ideal for my motor.

Can someone please provide me with some insight...number's to look for, brands to pay attention to, or even let me know if the number of pole-pairs is too high to expect reasonable control. I can re-jig the numbers at the possible loss of performance if need be.

Any help would appreciated.

Regards,

- Matt


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## DavidDymaxion (Dec 1, 2008)

By teeth I assume those are armature "pole" faces, like in a switched reluctance motor? How is your motor different from a switched reluctance motor?

I'm no expert -- I'm having trouble visualizing how you are going to line things up. 3 phase is a natural way to drive things as it makes it easy to define a forward direction vs. a backwards direction. You can then wire poles as ABCABCABC... it takes only six switches no matter how many poles you have, provided you have a multiple of three for the number of pole pairs.

16 field pole pairs is could be done (ABCDABCDABCDABCD), that would require 8 switches, is that the plan? Then it's hard for me to visualize how you are going to line up with 15 teeth -- did you mean 14?


modern_messiah said:


> I all,
> 
> Quick question because I am _very_ new to this and am doing some research before I bite off more than I can chew.
> 
> ...


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## modern_messiah (Dec 8, 2010)

You've confused me a little bit so I'll explain what I'm talking about a bit more clearly (I hope!).

Teeth are the windings in the stator between the 2 rotors. There are 15 so seen as it's 3-phase thats 5 'teeth' per phase.

The poles are the magnets. There will be 16 magnets on each rotor, so 16 pole-pairs. The winding scheme I plan to use can be found here: http://fast-results.com/lnl/nutpol_e.htm

16 poles with 15 teeth is an optimal match.



> it takes only six switches no matter how many poles you have, provided you have a multiple of three for the number of pole pairs


Can you please elaborate on this more? I can't seem to work out the 'six switches' part 

Thinking out loud now:

You only need three sensors to determine the rotor position (at angles of 120 degrees apart - I'm assuming this is the same for *all *3-phase motors) and seen as there are only 3 phases you only need to control three input signals. It's not like all 15 teeth are independent of each other!

How does this depend on the number of pole-pairs? Or are the controllers controlling something else? Am I missing something pretty obvious here?


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## frodus (Apr 12, 2008)

modern_messiah said:


> Can you please elaborate on this more? I can't seem to work out the 'six switches' part


3 positive Switches, and 3 negative (IGBT's or FET's) so you can create a sinusoidal waveform.


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## modern_messiah (Dec 8, 2010)

Ah my bad lol. Simple stuff really. I just have so many things going through my head I keep missing the obvious parts.

Can someone confirm/deny that my "thinking out loud" part is correct? Because that is what's doing my head in most at the moment!


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