[BrianG]

Delta wind looks like a triangle. Each end of the coil is a point on the triangle with each coil as one of the sides. Wye wind looks like the letter Y with one end of the coil at each end point of the Y, the other end of all three coils are tied together at the junction of the Y. The coils make up the "legs".

Generally, the Y wind is used in 3-phase industrial AC because there is a common neutral lead. This creates the 120v from each lead to this common point and each is 120 degrees out of phase from each other. Obviously, this requires four wires (one of each point and the neutral). Delta is used to transmit high voltage AC across long distances on the high tension power lines. There is no need for a neutral or common lead here. The biggest advantage is that it requires one less wire so it saves money on the physical wiring. Ever notice how those high tension wires are in three? That's why (or should I say "not wye", lol ...I know, bad pun).

If our BL motors are wired in Y configuration, the center point isn't a lead, it's just a common point in the motor. Only the ends of the Y are hooked to the motor leads. However, the signal has to go through two coils instead of just one. This increases the resistance, reduces the current, and splits the voltage. So more voltage can be used. The signal going to a delta-wired motor goes through only one coil at once (less resistance/more current/less voltage is needed). Actually, it's a little more complex than this because of the 60 degree out of phase thing, but that's a basic example.

[edited for error]