Brushless delta or wye wound - how to tell?
 

Hi All,

I am new to electric flight and learned that BL motor windingscan be either "delta" connected (like a triangle), or "wye" connected (like a star). Both have three phase leads of course. Here is the question. If I have a BL motor, how can I tell without asking the manufacturer or physically dismantling it and tracing the wiring? I did some resistance calculations for the theoreticalchange in DC resistance based on measuring across just two phase leads, then measuring with two of them shorted together. Guess what - my calcs show the exact same change in resistance for both types so I can't use this technique to determine how the windings are connected. I was thinking that I need to inject a pulse and see if it returns (using an oscilloscope) since the delta has "feedback" and the wye does not.

Anyone have a simpler way to do this?

Art

RE: Brushless delta or wye wound - how to tell?
 

Somewhere in that tread there must be an answer!
http://www.rcgroups.com/forums/showthread.php?t=587549

RE: Brushless delta or wye wound - how to tell?
 

Actually there is no way to tell as they are equivalent. It would be the same as having two 50 ohm resistors in series or two 200 ohm resistors in parallel. Same o - same o.

RE: Brushless delta or wye wound - how to tell?
 

It's hard to tell, but there is a big difference when running the motor on DC, wye is better.

RE: Brushless delta or wye wound - how to tell?
 

Hi Dave -

Could you explain your statement, please? I've built a bunch of brushless motors for R/C use, and while there may be good reasons to select either a Wye or Delta termination, I've never noted that one was always "better" than the other. Doesn't it depend on what you want the power system to do (big prop/small prop, torque/speed, direct drive/gearbox, etc.)?

As for how to determine the termination of a given motor, in some motors terminated as Wye, you can actually see a little stub where the three phases are connected together. Delta won't have that.

- Jeff

RE: Brushless delta or wye wound - how to tell?
 

Last summer I rewound a 4020 size motor and brought out all six ends. With the motor mounted to a digital torque wrench I measured the Kt and found the wye had a higher Kt than I expected and got more rpm per watt.

RE: Brushless delta or wye wound - how to tell?
 

Thanks Jeff,

I'll look for the wye stub you described.

There is a difference in low end torque and upper RPM between the two winding types. I believe the delta provides higher torque but lower maximum RPM and vice-versa for the wye (assuming the same numberof turns and poles of course).

Art