Brushless Motor with Convertible Delta or Wye Winding
I had built a little brushless motor for a plane I was building, and trying to decide how to terminate it.
After pondering the possibilities of going with a Delta wind versus a Wye wind on my motor, I just could not decide which way to go, so I did both!
How do you do that you say? It has to be one or the other, right? Well, not any more!
To pull this off I came up with the idea to bring all 6 wires out from the motor to a termination board, then make 2 different wiring plugs to connect between the motor and the speed controller. One of them would tie the windings together in a Wye configuration, while the other one would tie the windings together in a Delta configuration. Here is the step-by-step process that I used.
First I had a home-made CD-ROM brushless motor. This one has a 20.3mm stator wound with 17 turns of 26ga wire in an AaABbBCcC configuration with ten 5x4x1mm N50 magnets in the rotor can. The bearing tube is turned down from a piece of 3/8" bar stock.
To terminate the windings I came up with this idea. I took a 1" hole saw and chucked it up into my drill press. Then I cut out a piece of copper-clad 1/16" fiberglass PC board with the hole saw. After the washer shaped piece was removed from the hole saw, I drilled the center hole out to 3/8" diameter so it would be a good fit on the bearing tube. To finish the part, I countersunk the hole on the copper side of the board to make sure that the copper did not touch the bearing tube once the part was mounted. Here is what the piece looked like at this point.
Since I had 6 wires to terminate, I drew lines to segment the termination board into 6 segments as shown below.
Next I took my Dremel tool with a cut-off wheel and notched the copper along the lines to divide the copper into 6 seperate segments.
After I had the segments cut, I used a #60 drill to put 3 holes in each of the 6 segments to run my wires through so they could be soldered to the copper.
At this point I took a fine tipped Sharpie pen and wrote the phase designations on the termination board. I also opened up 2 holes in each segment with a #55 drill bit to accept the 20ga wire I was going to use to connect the motor to the speed controller. The smaller holes are for the 26ga motor winding wires.
After I had the board marked, I soldered the lead wires in place. I stripped the insulation on the wires a little longer than I needed. I ran the wire into the center hole of each segment, then wrapped the wire back around through the other hole in the segment, and then soldered both ends of the wire. This was done to provide a good mechanical connection from the lead wire to the termination board. his way, it would be very difficult to pull a wire off the termination board. Here is the termination board with the six 20ga lead wires soldered in place. I used 6 different color wires to mak it easy to keep track of them later.
To prep the motor for installation of the termination board, I sanded the bearing tube a little bit with an emery board about 3/16" behind the stator. This was done to provide a good rough surface for the epoxy to stick to when the board gets glued in place. I also trimmed the motor winding leads to a length of about 3/8".
I used my soldering iron to burn the enamel off the ends of the motor winding leads and tinned them so they were ready to solder into the termination board. next, I test fit the termination board onto the bearing tube. It fit a little tight, so I opened up the center hole slightly with my X-Acto knife. When I was happy with the fit, I mixed up some 5-minute epoxy, slid the termination board into place, and glued it into place. After the epoxy cured, I soldered the motor winding wires to the termination board. Here is the motor at this stage.
And here is a back view of the motor with the termination board in place.
Next, I dressed up the motor leads and tie-wrapped them together in 2 bundles. After I had the wires lined up, I snipped off the ends to even them all up.
To finish the motor, I soldered the connector to the end of the lead wires and put heatshrink tubing on all the connections.
Now I had to convert the 6 motor leads into 3 for the speed controller, and at the same time tie the leads together in a Wye configuration. To do this, I took a 6-pin mating connector for the motor and wired it as shown below. Pins 1, 3 and 5 are the Phase 1A, Phase 2A, and Phase 3A leads and run back to the 3-pin connector that will attach to the speed controller. Pins 2, 4 and 6 on big connector are the Phase 1B, Phase 2B and Phase 3B leads, and the little red jumper wires tie all three of these pins together to complete the Wye configuration. Here is a photo of the completed Wye adapter cable.
Here is the Wye adapter connected to the motor.
And here is the completed motor assembly attached to the Brushless Speed Controller.
To complete the package, I made another adapter cable to terminate the motor in a Delta configuration. In this one, pin 2 and pin 3 are tied together which connects Phase 1B to Phase 2A. Next pins 4 and 5 are tied together which connects Phase 2B to Phase 3A, and finally pins 1 and 6 are tied together to connect Phase 3B to Phase 1A. Here is a photo of the Delta wiring adapter (with the white wire) next to the Wye wiring adapter (with the yellow wire).
This motor draws a little under 2 amps on 2 Li-Po cells with a 5-1/4 x 4 prop when wired in the Wye configuration. In the Delta configuration, it draws about 5 amps on the same prop, but it also turns about 2500 RPM faster (11,200 in Delta vs 8,700 in Wye).
Now, when I go to the field, if I am in a slow-fly mood, I can set the motor in a Wye configuration, slap on a 7x3.5 prop, and fly for 30 minutes on a charge. If I want to go fast, I can change to a 5x5 prop, plug the motor in as a Delta wind, and tear up the sky. (Sort of like having your cake and eating it too, with a slice of pie to go with it! )
I must admit, it did take a while to do all this motor wiring, about 2-1/2 hours all together. However, It will be worth it out at the field with the flexibility that this system offers. This process can be modified to fit any brushless motor, so give it a whirl.
The way I laid out the wiring on the connectors, it is not possible to hook it up wrong. If I accidently plug in the Delta plug the wrong way, it effectively has the same wiring scheme since it is a mirror image with regards to the center pins. If I plug the Wye connector in the wrong way, I will just feed the B end of each phase with all the A ends tied together, so the motor will just run backwards. And this leads me to the next cool thing about the way I wired the connectors. If the motor does run the wrong way, you just flip the 3-pin connector over and plug it back in. This swaps the outer 2 wires, and leaves the center one the same. And as we all know, if you swap 2 wires on a 3-phase motor, it will run the other way! Cool!!
If anybody decides to try this, let me know how it works out for you.
Joined Nov 2003
Nice work Lucien,
I will try this on a motor. I think I can comfortably create or come up with the parts you made and used.
I am so happy to see your ditto site up and running again. www.powerditto.de
I depend on it for almost every idea that comes into my head. All of us here owe you a tremendous amount.
your humble servant,
Last edited by Eljimb0; Jul 12, 2005 at 11:41 AM.
I posted about the option of using a relay to perform the swap in flight. I have a servo controlled relay, but need to get a smaller one with more poles. I think this setup could really shine when combined with variable pitch props.
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