Wye vs. Delta
 

I just found some info on this that makes sense...

"Wye" wind Motor

Draw 3 resistors (or coils) radiating from a central point (The Wye tie). label the three ends A, B, and C. These represent the three phase connections in the Wye motor.

In the controller, each of these has 2 pair of MOSFETs connected to it, a pair to source the current, and a pair to sink the current. The motor fires something like this (simplified for clarity) A-B, A-C, B-C, B-A, C-B, C-A ad nauseam. The Magnets 'chase' the rotating magnetic field. Notice that there are always 2 phases 'commutated' at the same time, but the mix differs, and the current direction will reverse every other time. The motors resistance is the sum of any two phases i.e.. measure from any 2 phases. the third phase is open electrically when any other 2 are commutated.

"Delta" wind Motor

Draw 3 resistors connected in a triangle (delta). Each of the vertices is a phase. When you commutate CA-AB, you get most of the energy on one coil, (A), but some on (A-C-B) side. (mostly losses imo). The net result of most of the current going through one set of coils at a time, instead of 2 is that the Kt is cut in half and Kv doubles.

At Aveox, we have essentially deemed the Deltas as secondary to Wye winds in any application, except where very high degree of uniformity in both directions is very important. Things like robots that move in both directions equally put up with the efficiency losses. Since the motors are very insensitive to timing changes (unlike the Wye winds), you don't have great performance in one direction, and poor in another (without adjusting the timing), you have good performance in both (but it isn't worth the losses in a model).

They have been discontinued at Aveox for a couple of years. We do whatever we can to get them out of circulation, by changing them over at a loss. (But they are really easy to make if you insisted, and I would feel guilty afterwards). When you finish winding a stator, you have 6 wires coming out, the start and finish of each phase. connect every other one together to make the wye tie, or adjacent pairs to make the delta.

I wonder if some of the problems I've heard about are due to the wye winds going in the wrong direction when put in a surface vehicle. Do the Wye's come with instructions on how to adjust the timing??? (AAngel, did your Neu have these instructions?)

I want a Wye now, but will it work right?

try the search, this passed by before.

Yeah, I thought it had but we were talking about it. (meant to put it in a different thread...)

That thread doesnt go into the wye timing. If its timed to go the wrong way what do you do?

Couldn't you just switch two of the power wires? I've always known that as the standard way of reversing a sensorless motor.

exactly

Blipo, with the Neu motor that I got, the only instructions were about using mild timing settings; however, I did get on Neu's website and under the FAQ section, they do explain that you can gain some performance benefits by going to a medium timing setting with the Wye wind motors, but also explain that Delta wound motors do not see any performance benefits from increased (or should I say advanced) timing and recommend that only low timing be applied for the Delta wound motors.

The initial post at the start of this thread has me a bit worried. I'm going to assume that the statements made by Aveox are generalities which apply to Wye wound brushless motors. If they are, then which way does the motor need to be turning for it to run great and NOT suffer from poor performance.

I recently purchased a 1512 1.5Y which was supposed to be a 1900kv motor. When I wired it up, my impression was that the performance sucked. I don't know everything, but I do have enough experience to know what a 1900kv motor on 4S lipo should perform like in a truggy. I could only conclude that one of two things happened. Either the motor was defective, or it was mislabeled at the factory. Since these motors are hand wound, and therefor subject to human error; it could have been either. My reason for thinking that it was mislabeled was that it ran too good for something to be wrong with it. The more I geared it, the better it got. When I put 5S on it, it came to life, so I figured that I had gotten a 2Y (1400kv), rather than the 1.5Y that I was supposed to have gotten.

Now that I read this thread, I'm wondering if the motor was just turning the wrong way. I wonder how the way a Wye wound runs would be affected by running the motor with the Quark controller. The information provided by Aveox suggests that performance in either direction would be equal, if timing corrections were made when changing directions. The Quark employs an automatic timing technique which is supposed to set the timing to whatever is ideal.

My question now is...what direction does the motor need to turn in to realize its full potential?

BTW, I also got an email back from the vendor that I bought the motor from. He said that mine was the second this month that had to be sent back to Neu. The other had to be sent back due to the motor shaft sliding out of the endbell. I also have to add that I got Neu on the phone. They were very curteous and nice, but after having gotten off of the phone I realized that the person hadn't actually told me anything. It seemed like she was talking in circles. The emails were like that too. All I know is that they received my motor last Thursday. When I enquired by email, the answer that I got only confirmed that they got it, which I know already. The email did not say anything else.

On a positive note, I haven't heard of anyone complaining about the performance of either the Delta or Wye wound Neu motors. The added efficiency that you get with the Wye wound motors is supposed to be negligible.

I suppose I'll just have to wait and see, which absolutely sucks.

Oh, and as for switching the wires, if you do that, then your vehicle will be going backwards, won't it?

I was talking about timing. My post says that a wye works better in one direction then the other(a result of 'timing'). (the only advantage of delta is that it works equally well in both directions)
So.... will reversing direction (by changing 2 wires) also reverse the timing, and how do you tell which is the good direction and which is the bad direction. And further, if your ESC wont let you reverse your throttle setting how (or can you) reverse the timing if its set for the wrong direction?
Anybody getting any of this???

If it was running backwards if you give a WOT before you switched the plugs, it will run forwards after..

O.k. yeah you got it AAngel.

I'm interested to see what happens with your motor, it sounds like wye wind is more efficient going one way then the other, seems there should be some arrow or sumthin to point the good way...

Timing, with sensorless motors, is maintained by back-EMF (timing) pulses through the three motor wires. Thus, if the motor is operated in reverse, the controller recieves the back-EMF pulses in reverse order as well. Timing isn't affected in either direction, so performance should remain constant in both directions as well, no matter which wind you have in the can.

Maybe I'm not following this, but the back-EMF pulses always happen after the initial signal. So, if the motor was operated in reverse, the feedback pulses would still be happening in the right order. If what you are saying is true, then the ESC is firing coils when it is not supposed to? I would think that would cause a LOT more damage than simply being less efficient. Akin to firing a spark when a piston is on the way up in the stroke!

I can't see there being a performance hit, or anything running a brushless motor in reverse. (or even really being a reverse...)

Are these controllers sensing the sine wave naturally generated by the motor, or kick back from switching pulses? I would think it would be easier for a controller to sense motor position by the sine wave method. IMO

I wouldn't bet on the feedback being a "sine-wave". Don't forget that we are feeding square waves to a coil. The inductive kickback is usually a large spike - the amplitude dependant on the inductance value, how quickly the field collapses, and voltage.

Yes, but there would also be a natural sine wave present/super imposed in the signal as well.

The BEMF pulses are what tells the ESC where the rotor is relative to the stator coils. When one pole of the rotor passes under a coil, it sends a pulse back to the ESC. The ESC then "knows" that this particular pole (N or S) is 60 degrees from the next coil, and can determine when it should fire the next coil. Have you ever wondered why sensorless motors "cog" only at low speeds, or very high gearing? It's because the rotor's speed is to low to send accurate pulses to the ESC, and in turn the ESC can't accurately calculate timing.

OK, there you guys go again, turning a nice pleasant exchange into a lesson in electrical engineering. All of which went right over my head.

Hence, sine wave...

Sorry about the techno-babble AAngel. I can't help it. And yes ZPBug, the pulses are in fact a perfect 3-phase AC sine wave. Assuming a 2-pole motor.

I still don't think the feedback pulses are perfect sine waves. You are applying a high current square wave signal to a coil. When the field collapses, it will generate a back-EMF spike. However, since this is happening kinda fast, the spikes aren't as bad as they normally would be. It probably looks more like a semi-sinusoidal pulse with a little decay before the next pulse from the ESC comes in.

Now, if we were talking about variable frequency sine-wave drives, then yes, the feedback would be a perfect sine wave. Man, I wish I still had access to a o-scope to check this!

If you think that's bad listen to this:
http://video.google.com/videoplay?do...ell+automation

Thank you silentbob343. That, was awesome. I understood every word out of his mouth. It's sad, because half of them are made up; sinusoidal deplanaration, capacitive deractance, etc.

Yes we are giving the coils square wave drive pulses, and the BEMF would also be a primarily square wave. But, the BEMF pulse is influenced by the present magnetic field to the effect of a sinusoidal wave being factored in as the rotor passes each coil. The same is true for wye winds or delta winds. So if you filter out the inverse of the drive pulse, timing included, you'll be left with a sinewave.

I was just about to post that exactly. Well said.

Oh, seen the video before, love it.:005:

Ha! I win! But seriously I would prefer the wye/star wound motors because of their increased torque output. That's basically what it comes down to when your talking electric power. You will always be able to gear up more than you can gear down. Plus, running higher voltage and lower current for the same power equals higher efficiency.

yeah it has been floating around the internet for quite some time, but never gets old.

O.K., Technobabble aside, I thought ALL BL timing was in the controller too, however the more I read the more it seems there is some 'timing' built into the can as well, (and wye is very sensitive to it (I'm assuming)).
The only thing I could think of as 'directional' (or 'timing') in any way would be the direction of the current in the stators, (the direction of the 'wind' in conjuction with the width of the stators...) Wouldnt it be 'timed' to work better one way. (maybee Delta cancelles this out and wye makes it more pronounced...(gaining a bit of efficiency in the favored direction...)
However, NEU's (and most BL I think) are made for planes, so counter-clockwise should be the 'right' direction. (this would be of no help to AAngel's problem, you were going CC anyway right?...)

Don't quite remember who posted this;

saying a Y is always sqrt 3 stronger than a delta;

not true; if they have the same windings, with the same amount of wire used, then yes, if they are matched on KV, then this is not the case.

So it's not a fact a Y is by definition 1.72 times stronger in terms of torque than a delta.

Like when you reconfigure a Lehner from delta to wye; you multiply torque by 1.73, but also divide the kv by 1.73.

Yeah, but that changes the KV, which also takes the torque with it;

What if you have a Y with a kv of 2000, and a delta with a kv of 2000, in that case, the torque isn't sqrt 3 higher for the Y. So it's not a fact a Y has more torque than a delta. Get my point?

Yes, i agree, it's whatever Kv. you have. It is per equivalent turn count.

I just read briefly over most of the posts in here (good stuff guys; understood a good deal of it, woooo!), and I may have missed it, but could it be perhaps Aveox (as was copied and posted by the OP) was referring to sensored motors?

The only way I've experienced a wye wound motor acting poorly is running my Novak in reverse direction (this is on a sensored ESC though; I've never tried it on my mamba or anything yet). Performance goes down hill big time. The timing in those motors is "built in" by the Hall sensors, so it's like running retarded timing when run backwards, no?

If they're referring to strictly sensorless wye and delta winds, then I have no idea what the hell they're talking about, and you should probably ignore my post.:D