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 Explanation of Delta and Wye wound brushless motors

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snellemin



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PostSubject: Explanation of Delta and Wye wound brushless motors   Mon Jun 21, 2010 10:41 am

I was asked recently the difference between Delta and Wye wound brushless motors. Here is the explanation between the two winds by Aveox.

"Q. In a brushless motor system, what's the difference between a Delta wind and a Wye wind? What are the advantages and disadvantages?

A. Get a pencil and paper for this. <There's not a nice way to do this with ASCII art>

"Wye" wind Motor

Draw 3 resistors (or coils) radiating from a central point (The Wye tie). Label the three ends A, B, and C. These represent the three phase connections in the Wye motor.

In the controller, each of these has 2 pair of MOSFETs connected to it, a pair to source the current, and a pair to sink the current. The motor fires like this (simplified for clarity) A-B, A-C, B-C, B-A, C-B, C-A ad nauseam. The Magnets "chase" the rotating magnetic field. Notice that there are always 2 phases "commutated" at the same time, but the mix differs, and the current direction will reverse every other time. The motors resistance is the sum of any two phases i.e. measure from any 2 phases. The third phase is open electrically when any other 2 are commutated.

"Delta" wind Motor

Draw 3 resistors connected in a triangle (delta). Each of the vertices is a phase. When you commutate CA-AB, you get most of the energy on one coil, (A), but some on (A-C-B) side. (mostly imo losses). The net result of most of the current going through one set of coils at a time, instead of two is that the Kt <torque constant (tm)> is cut in half and Kv <motor constant, RPM/volt (tm)> doubles.

At Aveox, we have essentially deemed the Deltas as secondary to Wye winds in any application, except where a very high degree of uniformity in both directions is very important. Things like robots that move in both directions equally put up with the efficiency losses. Since the motors are very insensitive to timing changes (unlike the Wye winds), you don't have great performance in one direction, and poor in another(without adjusting the timing). You have good performance in both. (but it is not worth the losses in a model)"



So basically the Wye will spool up faster and reach its top RPM a bit faster than the Delta wound motor. The Delta wound motor also consume more amperage than the Wye motor. If you want a hi-torque motor, the Wye-wind will let you do it with few turns. If you want speed, the Delta motor will let you do it without having to use difficult, thick wire or mess with parallel strands.
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PostSubject: Re: Explanation of Delta and Wye wound brushless motors   Mon Jun 21, 2010 3:53 pm

Nice Electrical Engineering stuff something they dont teach you in school !!!
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snellemin



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PostSubject: Re: Explanation of Delta and Wye wound brushless motors   Mon Jun 21, 2010 4:03 pm

YUP. I only got a wiff of it in Robotics class.


Mark has my older 1515 1.5 Delta wound motor and that thing is a beast. Eats diffs like TikTak's.
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Explanation of Delta and Wye wound brushless motors

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