In-flight change from delta to wye wind (and vice-versa)?

[Bigfoot]

I have just read in the model press about a Sunrise-Sunset competition team who used a small brushless motor. They apparently changed from delta to wye wind and back in flight, using a servo-driven cam and micro-switches. This was in order to use the ESC at full power all the time, since it is in this mode that an ESC is most efficient (least power loss). The figures quoted were 100W for climb-out and then 22W in cruise mode.

Do you think this is really possible, is it rational, and if so, how is it done?:confused:

[Ollie]

It would be rational if the power loss by adding the switching circuits were less than the diffference in the powerloss in the ESC and motor in the two winding arrangements. The delta and wye connected motors will probably also have peak efficiencies at different power outputs. I wonder how well the condition for rationality is met in practise. I think it would be difficult to find low voltage drop microswitches for high currents. I think the switching arrangement would work best with a high voltage, low current power source. The circuit would require three contacts in a transfer arrangement at each end of each winding. That is a lot of contacts and potentially, a lot of switching loss. It would be two contact pairs carrying current at any instant and six contact pairs carring current at some point in the cycle.

[dw1122]

Provided you have the motor with all 6 wire terminals brought out, a ESC with 6 instead of 3 driver stages will do the trick better than cams and servos and contacts. The ESC firmware will drive the six outputs according to the need for Y or Delta configuration.

[Trizza]

This is often done in large three phase motors. I'm sure it would work well, but as dw1122 says it would be better to have it electronically done than mechanically. Lower weight, lower resistance.