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[concept] Dynamic Wind Switching on-the-fly Y/Δ changing

#1 User is offline   aotsukisho 

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Posted 23 March 2011 - 12:47 PM

Reading up on several forums, I came across the concept of dynamic wind switching, usually done on outrunners. The theory behind this is that for the same turn count, a delta type termination has 73% (√3 = ~1.732) times more Kv, less torque, higher current draw and slightly reduced efficiency. This is more or less equivalent of changing gearing, and if it can be done on-the-fly then a two speed application can be direct drive (no transmission required). Of course, the motor has to be able to handle the extra heat dissipation (robust wye-type motors) and batteries to handle the amp draw.

Some graphics to illustrate the difference between delta and wye windings:

Posted Image
A wye, or star, winding. If each of the coils were removed from the stator, each color would correspond to a leg of the letter Υ. The 'solder together' bit is the center, and the three motor terminals are at the tips of the Y.

Posted Image
Here is a delta winding. If you remove the coils from the stator, each color would correspond to a leg of the letter Δ. The three motor terminals are at the points of the delta.

I think it is easiest to implement a relay system to control the configuration of the windings, as it is the most robust and will work with 3s or 4s lipo (what most of my outrunners can run at). However, an obviously better solution will be solid state MOSFET switching. I will throw together some ideas and see where it takes me.

References (so far):
Endless-sphere: The State of Wye-Delta Switching
Motor Building Info
RCGroups: Delta versus Wye
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#2 User is offline   aotsukisho 

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Posted 28 March 2011 - 03:45 PM

drew up a schematic that implements relays.

Posted Image
very simple. now I just have to either get a motor that will run under 40A, or get some super robust 80A relays.

Also, I attached the schematic in ExpressSCH format.

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