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 In a brushless motor system, what's the difference between a delta wind and a wye wind? What are the advantages and disadvantages?

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. Matthew Orme, Aveox Inc. mailto: 102252.401@compuserve.com

Get a pencil and paper for this.

"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 something 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 losses imo). The net result of most of the current going through one set of coils at a time, instead of 2 is that the Kt is cut in half and Kv doubles.

At Aveox, we have essentially deemed the Deltas as secondary to Wye winds in any application, except where 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 isn't worth the losses in a model).

They have been discontinued at Aveox for a couple of years. We do whatever we can to get them out of circulation, by changing them over at a loss. (But they are really easy to make if you insisted, and I would feel guilty afterwards). When you finish winding a stator, you have 6 wires coming out, the start and finish of each phase. connect every other one together to make the wye tie, or adjacent pairs to make the delta.