I've been doing some more research about this on my own.

Delta has 1.72 times the kv as Wye Termination but draws 1.72 times the amps.

Wye has 1.72 times the torque as Delta, but draws 1.72 times less amps.

SO, correct me if I'm wrong, but to make the Wye termination put out the same wattage and KV, You must use 1.72 less winds on the stator.

There are two big advantages of the Wye termination IMO.

1. More Torque! 1.72 times as much torque. I think this is mainly due to the fact that 8 magnets/poles are in use at any given time, rather than 4 magnets/poles on the Delta.

2. More EFM feedback to the ESC at lower rpm's. I just discovered this today as I was reading about this. The Wye should run/start MUCH better in a Car/Truck Application.

I'm thinking about taking a short cut to the entire winding/experimenting thing. AXI motors says "If you have a custom motor in mind, do not hesitate to contact us."

I think I'm going to ask them if they can do a custom wind for me. I want a 4130/8 with a Wye Termination. I want to shoot for 700kv and with a Wye Termination, this should be a BEAST! :yes:

That is correct, a delta terminated motor needs 1.72x the winds to match a Wye terminated motors KV. The D termination has less resistance since there are two parallel current paths in any phase.

I think you are getting a bit ahead of yourself on the torque though. While yes you will have 1.72x the torque with a Wye termination (per amp), the amp draw will go down. If you don't change your voltage the torque (and wattage) will actually be lower since torque and amp draw are directly proportional. If you volt back up to the same motor speed your torque will again be the same, but at a lower amp draw since the kt is of higher value with a lower kv motor. A 1200 watt motor is a 1200 watt motor, and the torque curve is almost perfectly linear for a permanent magnet motor no matter what the wind or termination.


The increase in EFM feedback should be correct though, plus higher voltage motors give better feedback anyway. Although the motor doesn't have higher torque, the ESC should see the motor better in effect making more efficient use of the torque.


It really wouldn't be hard to take a motor apart and just change the termination.

I feel like there must be a good torque bonus if only based on the fact that it's pulling on 8 magnets with each phase instead of 4.

Yes motor timing will be more accurate especially at low speeds.

I've thought about taking one apart and changing the termination, but let's look at an example.

The 4120/14 that I'm running is 660kv. By using the same 14 turn winding and changing the termination, I'm cutting the kv to 384kv. Even though torque would be increased by 1.72 times, the 384 kv isn't enough to do the trick. Unless I wanna go HV. Hmmmmmmm.........there's an idea!

The is where more strands and less turns comes in.

I plan on consulting with the winding guys at AXI about this. Let's see what they say. :yes:

John, there is alot of valuable motor building information here.

Just trying to pass along some tools that I plan on using.

http://www.bavaria-direct.co.za:80/m...motor_info.htm

I don't know if theory alone can explain this well, there are so many variables. When any phase is excited, delta energizes all three coils at a time whereas Wye only excites two. If kv is the same between termination styles the amp draw will be the same, and since kt and amp draw will be the same the motor torque will also be the same.


Change the magnet count or stator count- motor power will change. Change the size of the motor, motor power will change. Change the winding of the motor, motor power only changes in respect to voltage.

One thing that I thought was very interesting is at the bottom of that page. It's how to figure the kv of any motor that's already built.

"Drive your motor with a power drill.
Measure RPM and voltage generated.

Kv = RPM / voltage"

I spun the 4130 at 930rpm with a drill. It was feeding 2.9 volts into a volt meter on the AC scale.

930rpm/2.9volts= 320kv

Pretty close to the factory rating of 305kv! Which maybe with the load of the motor, the drill wasn't quite spinning at 930rpm. I think this is a good quick method though.

The generator method gives you the kv with consideration to efficiency losses in the motor. Factories do not always do this, and it could explain the small difference you found. Pretty darn close though.

Yes, there are many variables.

Total Power output also changes in respect to Amp draw. Total watts of power.

The way I understand it, on a 12 pole motor:

A Delta Winding has 4 poles energized at a time.

A Wye Winding has 8 poles energized at a time. but they are 4 x 2. 4 sets of 2. The amp draw is lower for identical turns because the pairs of windings are in series to each other. This drops the amp draw by 1.73 times along with the kv. but raises the torque by 1.73 times.

I guess what I'm really wondering is, if we drop turns to raise the kv back up in a wye winding, will we retain the added torque bonus along with the improved EMF feedback?

Here's what Lucien had to say about this when we were discussing a high kv wind on a 4045 Scorpion motor. (note: 700kv wye wind will be easier on a 4130)

Here's what I asked him:
"Would it be possible to wind a 4045 to around 800kv using larger diameter wire, such as 22 awg, using a wye termination for a 1.73 torque bonus? (Minimize copper losses and keep operating temps to a minimum?) I noticed that with a wye termination, it uses 8 magnets, 8 poles at any given time. I'm not too concerned about amp draw or total efficiency at this point. I'm just looking to have some fun and learn more about 3 phase windings and how they perform."

Here's his answer:

"It would be very tough to wind a 4045 with a Kv of 800, especially with a Wye wind. THe current 4045-10 has a Kv of 360, the 4045-12 has a Kv of 315, and the 4045-17 has a Kv of 270. These are Delta wind motors, so if you switch to a Wye, the Kv will be lowered by a factor of 1.73. A 4-turn Delta would have a Kv of about 800, but you would have to wind about 50 parallel strands to get enough copper in the slots.

The larger motors are made to run on 10-12 Li-Po cells to be able to get enough power to run the motor, and that is why they have a much lower Kv.

Think that over and let me know what you think."

I keep notes on all the information I've collected. :lol:

Now keep in mind that the 50 strands that he is referring to is 31awg. Total Cross Section area of the wind and total resistence is what we need to look at. In other words, we can use a much larger Ga. wire and eliminate the whole 50 strands thing.

I'm sure the end product of what I'm trying to put together will DEFINATELY be a high amp draw motor. But that's ok, that's what I want. Total Watts is Total power.

I want to run this on 4S Lipo or more. It's ok if it draws 100 to 150 amps continous.

I asked AXI about motor kits for the people who want to wind their own motors. Maybe they have those.

If you raised the kv back up to negate the wye termination, you would indeed lose the torque bonus.

Kt = 1352.4 / Kv By this formula the torque constant and kv are directly related for any and all electric motors. Like I said before, if the overall construction of the motor is not changed the power of the motor wont change. Different terminations or winds only change the voltage and amperage that the motor will produce said power. The torque curve won't change, the wattage wont change, the motor is still the same motor.

I have fought this issue with guys at RCC for a while now. People thing a 65t motor will produce more torque than a 55t motor. Geared for the same wheelspeed they will produce the same torque and power if the rpm of the motor is also the same. This means a different voltage for the two setups. On the flipside, if gearing and voltage is held constant the 55t will have more power since it spins faster and has a higher amp draw. A third example is when wheelspeed is kept the same through different gearing with fixed voltage. A 35t motor on 3s lipo geared way down will have a ton more power than a 65t on 3s lipo geared for the same wheelspeed. Lower turns, but more torque through amperage and gearing. In your case you cannot change the gearing except with tire changes, so we have one less variable to deal with.

Between two identical motors with different winding:
Same gearing, same wheelspeed (indicates same rpm at motor), different voltages to hit said rpm. If the vehicle hits 60mph it will take the same wattage no matter what the motor if vehicle weight is constant. Same power, just at different voltages.


The aspect we are really going for is a better low speed commutation of the motor, correct?. Although the motor will have the same performance capability no matter what wind or termination, the ESC might do better with certain ones.


The 4045 is a huge motor. Getting a kv so high will be very tricky.

I understand what you're saying where different winds of brushed inrunner motors are concerned and I aggree with you completely.

Outrunner motors are different creatures with more magnets floating around. In the Delta, when the 4 magnets are being attracted to their energized poles, the other 10 magnets are just waiting their turn to do their work.

What makes me wonder, 8 magnets versus 4? My theory is, the 8 will win the tug of war.

If I'm wrong, then I just am. But if I'm right, why aren't they building them this way? For one thing, heat buildup. Wouldn't the heat be 1.73 times greater also? I'm willing to try this, since the motor in the Revo has ran so cool.

But yes, even if it's just the better low speed commutation of the motor. That would definately be a benefit worth pursuing.:yes:

They act no different than any other motor type. They are just permanent magnet motor and abide by the same rules as inrunners and brushed motors alike.

Even if one of us is wrong in our assumptions, it is still a great conversation! :lol: Until we get some real quantitative testing done we can't do much more than chat about it anyway.

Yes it is a GREAT conversation. You bring things to the forefront that I haven't considered.

I would like to stick with the AXI motor because of the cooling fan that I've mounted to the rear of it. Hopefully, AXI will answer my email soon.

Even if I can just get a Delta wound 4130 that makes 700kv, it will outperform this 4120 since it's stator/magnets are 10mm longer. It will make more torque.

The Revo runs well. It's powerful and efficient. I'm happy with top speeds and even the low speed driveability. I just want some more torque with the same top speeds. Along with the extra torque will come more acceleration.

With the 4S 5000mah Lipos, RTR weight is 10lbs 3 ounces.

I think more outrunner power can be had on the 4S setup with a custom higher kv wind on the 4130 motor.

The 4130 motor would match the top speed of the 4120, possibly even more, if I had the ESC and Lipo's to put it on 8S to 10S. But even then, we are talking more weight.

I'm really considering going with the Quark 125 amp Monster Pro. I should see a performance improvement because of the increased current handling ability. It also has less resistence accross it's power board.:yes:

I can barely imagine what kind of power a 4030 will put down. It will be interesting to see if the gearing or rollout threshold for startup will can be changed much with the extra motor size. Getting any more speed from your revo as-is takes a taller tire,hotter wind motor, or higher voltage. I really think the simplicity will help understand the limits of sensorless motor control.

I think I am right at the threshold for startup with the 4120.

It was surprising to see that the 4130 was only generating 2.9 volts at 930 rpm. I wonder what the lower and upper limits of the EMF feedback "window" really is?

I'm sure the design of the ESC has some reasoning in it that matches most setups out there. There is a resistor in each of the 3 lines on the EMF feedback leads going to the brain board. I'm sure those are there to raise the upper limit of the EMF "window", but it also raises the lower limit that can be seen by the ESC. I wonder what would happen if those were removed? I believe they traded some "lower" to increase voltage operating range. The Quark tends to cog more on fresh fully charged 6S Lipo. I'm sure it has to do with this. Removing those would probably make for better startups, but also might lower the voltage operating range to perhaps 4S or 5S.

I have a Quark 125 Monster Pro on the way now. Once it gets here, I may try to bypass those resistors on my 80 amp ESC as a test. Do something that is reversible just to see. I need to ask Griffin about this.

Vehicle weight has alot to do with this also. The ESC blindly (no EMF feedback) sends a "kick in the pants" to the motor for startup. If vehicle weight or gearing is so great, that the motor doesn't give the vehicle enough movement to get some EFM return, the ESC is "lost" as to armature position. This is when cogging occurs.

The 4130 did startup better than the 4120, but the top speed wasn't there so I switched. This leads me to believe that kv and stator length has something to do with this.

Aaaah, look at this.

"Kv = RPM / voltage"

I spun the 4130 at 930rpm with a drill. It was feeding 2.9 volts into a volt meter on the AC scale.

930rpm/2.9volts= 320kv"

With the higher kv of 660, using this formula, the 4120 at 930rpm is only going to generate 1.4 volts. :surprised:

The first EMF pulses must be VERY small and hard to see. Longer stator/magnets/winding changes that.

Hmmmm............This is where experimenting with different winding configurations could pay off. :yes:

AXI emailed me back!

"both ways are possible to provide you with set of parts for this motor. This we make really rare but in case you have it for some special application it is possible. Or if you tell use the winding we can make for you custom made winding."

What wye wind should I get to make 700kv?

Here's what I wrote them back.

"With a Wye wind, the torque is 1.73 times greater than the Delta wind but the kv is 1.73 times lower. If we negate the kv loss with fewer turns, will the torque bonus still be there?

Excellant! How much for the custom wind 4130? How much will the kit be?"

This should be interesting! :yes: