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Hi Christian,
In response to your post on rc line. It appears the newer double helix wind surrounding a two poles rotor each with an opening angle of 45 degrees would form a square ABC rhombic phase matrix under each pole with 90 degree resultant vectors? Each 180 degree coil set would be set at 120 degrees apart. Wouldn't the 4,8,10,12,14,16 higher pole counts increase the switching loss at high speeds?So for high speed it seems 2 or 4 poles would be better in terms of switching loss? What are the torque ripple characteristics of a skewed winding as compared to straight in a slotless motor?
Anyone else here is free to give answers as well.
Hubert
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In the meantime here is the BEMF scope shots @ apprx. 15.5k rpm from the SL MX700. Panned out to be 835 Kv on the optical tachometer. Compare the 2nd and 3rd photo taken at 2,250 rpm and you can see the harmonics associated with loss amplitudes rise with an increase in rpm . Still we can see the crest and troughs starting to flatten confirming a better trapezoidal BEMF for zero cross drives. A pure sinus has shown to be better for BLAC or but not superior to trapezoidal on BLDC drives. What most hobbyist use. The last photo was the Bemf and FFT analysis taken across a phase and the neutral line. I believes it illustrates the extra triplen current and noise in the neutral line. I could be wrong but clearly more harmonics are being produced here. This seems to agree with the academic explanation for 170% increase of triplen seen it the neutral lines.
Hubert
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This is a photo of new tech in the USA from Thingap. The IEEE confirm 30% more power density in printed or coils etched on flexible pcb.
http://www.rc-raceboats.de/forum/att...id=85570&stc=1
Hubert
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FYI
Ive found that actually Slotless winding dont have to be hard to repeat or "spaghetti". Rhombic or similar skewed windings can be repeated with a fair amount of consistency using a sliding mandrel. The patent for such a mandrel lies here in the US. Definitely does not have to be indiscriminately laid. In some slotless motors u can see a definitive pattern overlapping placing at least 1 wire from each phase under a pole.
Hubert