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Feb 19, 2017, 05:48 PM
Ronaldo Nogueira
ronaldopn's Avatar

First WYE termination, any downsides?

Hi folks, I'm about to do my first wind with WYE termination instead of Delta.
The reason for choosing WYE was simply the combination of turns and wire gauge which would get closest to the original cross sectional copper area.
I have AWG 19, 20 and 21 wire and don't want to use more than 2 wires in a strand. Here is the data:

Motor: Tomcat 30cc G160
Original kv=237
Original wind: 20 AWG28 10T dLRK Delta
Cross sectional area=20x10x0.081=16.2mm2

My target kv=210-215
Planned wind: 2 AWG19 13T hpdLRK WYE
Cross sectional area=2x13x0.653=16.978mm2

Now the real question: are there any downsides in the WYE termination? Probably not, but this is a big motor and I've always wound Delta so I prefer to ask.
Last edited by ronaldopn; Feb 19, 2017 at 05:59 PM. Reason: Add picture
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Feb 19, 2017, 07:12 PM
Registered User
manuel v's Avatar
not problem.
Any way, any wind is Ok.

Best copper fit is ever best motor. (low resistance)

Use TC 7.2 Block 4 and 5.
Feb 20, 2017, 07:37 AM
jackerbes's Avatar
I hate to argue with one of out most eminent motor experts here but I cannot agree that "..any wind is Ok..." when the Wye termination has fewer turns and an inherently lower resistance at the same Kv rating. That allows for larger wire and more current capacity over the same Kv with a Delta term.

And here are the words of Christian Lucas (whose name put the "L" in dLRK) for what type of motor is best:

"..rpm per volt and torque per ampere. Best 12 slot and 14 P with LRK winding ,always and yet and in the future.Only if you have a very short stator use dLRK winding. ABC winding only with 8P and 16P on 12N stator ,LRK and dLRK only with 10P and 14P for best result. To get high rpm/volt use 8P or 10P and for high torque use 14P or 16P with the correct winding..."

The image is how I typically do a Wye termination, I like it well insulated (two layers of heat shrink if it is the thinner type) and tucked in against the bearing tube and out of the way of any moving parts.

Last edited by jackerbes; Feb 20, 2017 at 05:41 PM.
Feb 20, 2017, 11:37 AM
Registered User
manuel v's Avatar
That's Jack.
Effectively there is better winding for a particular stator.
But from my point of view it is the same thing to do Wye that Delta.

If two identical motors, with the same scheme, but different termination, have the same Kv and the same Copper fit, both will have the same resistance fore phase and the same capacity to receive current.

I'm going to put an example.

I'm working in this.
Last edited by manuel v; Jan 16, 2018 at 02:08 PM.
Feb 20, 2017, 01:15 PM
Ronaldo Nogueira
ronaldopn's Avatar
Thanks guys, I'm glad to know the WYE could be even a better option as it allows me to use my thickest gauge wire.
Feb 20, 2017, 07:36 PM
Registered User
manuel v's Avatar
Now I have my explanation complete.

Last edited by manuel v; Jan 16, 2018 at 02:07 PM.
Feb 21, 2017, 05:58 AM
jackerbes's Avatar
Originally Posted by manuel v
Now I have my explanation complete.
And it is wonderful information! I am going to copy and paste the summary from Manuel's post on another forum here just to make sure that the info stays with this thread and discussion if the other thread ever goes away.

Manuel's details below are the best summary ever seen of the results of the various winding options!

Motor HXT 750 (HexTRONIK DAT-750 or HK DT750 motor)

Originally it has a DLRK winding,
18T, Delta,
Composed of 7 wires of caliber 30AWG,
80 inches in length.
Finished in Delta.
With a Kv of 750
Resistance per phase of greater than .061 Ohms.
Stator with an area of 28.2mm2 per slot.
A Copper Pack of up to 60.73%

In Star DLRK deals: 10T, 779 Kv, 43 inch, 18AWG, 64.79%, Rm = .050 ohms.
In Start HPDLRK deals: 21T, 742 Kv. 2 / 46.2 inch. 22AWG, 56.4%, R m = .062
In Delta HPDLRK deals: 36T 750 Kv.2 / 77 inch, 24AWG, 61.65%, Rm = .599
In Star LRK deals 20T, 742 Kv, 44.1Inch, 19AWG, 52.5%, Rm = .059
In Star LRK deals 20T, 742 Kv, 44.1Inch, 18AWG, 64.79%, Rm = .0469
In Delta LRK it is occupied 34T, 756 kv. 72.9 inch, 21AWG, 60.7%, R m = .052

Thanks again!

Feb 21, 2017, 10:42 AM
Registered User
manuel v's Avatar
Rm varies with the packaging and not with the scheme.

With the exception of LRK that occupies less Turns
For the same kv. (less wire longitude)
Feb 21, 2017, 04:41 PM
Ronaldo Nogueira
ronaldopn's Avatar
Really interesting info, guys. From now on I'll be seriously considering WYE (star) termination in my rewinds for lower internal resistance.
Fewer turns are also easier to count.
Feb 21, 2017, 05:52 PM
Registered User
manuel v's Avatar
The goal of rewinding an motor is to pack the largest percentage of copper inside the stator.
This will ensure that every phase of the motor has the least resistance.
As already said before for the same Kv. The LRK scheme occupies less wire vs the DLRK. Therefore the resistance will be lower.

But finishing it in Star or Delta is the same once you have achieved the above. Same Kv, Same% Packed therefore Same Resistance.

Then we should not worry about the termination. We use what suits us best according to the stator, the wire available and our ability.
Last edited by manuel v; Feb 21, 2017 at 10:24 PM.
Feb 21, 2017, 09:05 PM
I wanna build a Me-410
I have heard it said that with motor control wye is superior because you can be sure where the current is going in the motor. We were doing sine wave inverters for AC induction machines (not BLDC/PMAC), so this may not apply to our little permanent magnet RC motors. And I didn't write motor controller code for the AC induction motors at my work.

We did actually dynamically reconnect motors from wye-delta and back for better efficiency at different operating points in one application. This was a big traction drive application- electric transit buses utilizing a lot of regen braking.

It may not apply here.
Last edited by tigtig; Feb 21, 2017 at 09:07 PM. Reason: clarity
Feb 25, 2017, 07:02 PM
Ronaldo Nogueira
ronaldopn's Avatar
Well, finished the motor. The good news is that it worked. The bad news is that kv is much lower than predicted.
13T of hpdLRK WYE gave me 181kv instead of 211kv as TC5 predicted. I will test the motor on the plane as it is but will have to use higher pitch/ larger dia props. I was planning to use a 19x10 and now will probably have to go to a 21x10 our 21x12. If performance is not good I'll rewind it again.
Any ideas of what could cause such a big difference? I'm positively sure I did not miscount turns. My winding was far from neat (probably my worst job) but I don't believe this would explain the lower kv.

Feb 25, 2017, 09:09 PM
Registered User
manuel v's Avatar
As if you had put 15 turns.
Is the current without load lower?
How much?

Or the motor original wins is 9turns
Feb 26, 2017, 03:21 AM
Ronaldo Nogueira
ronaldopn's Avatar
I didn't check current on the original motor, Manuel, only kv.
I think I'll order another Tomcat to rewind as I have another 30cc plane still in the box. Once I get the kv I need I'll just swap motors and rewind this one again.
I really liked this Tomcat motor, very good quality and quite cheap.
Feb 26, 2017, 03:41 AM
Ronaldo Nogueira
ronaldopn's Avatar
I counted 10T on the original motor and it matches the specs. Here is a picture of the kv check (same I do for all motors). I really don't know what happened. The only new procedure in this rewind was the WYE termination (my first).

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