Lots of Delta vs Wye connection questions?

[BP-Revo]

Ok, I understand that Delta and Wye have some sort of relationship to the number 1.73, as in one provides that many times more (or less) KV than the other.

What I don't understand is which one is which compared to the ratings that we are given on the Lehner Motors.

Are the Lehner KV values rated in Delta or Wye? And please specify the differences between Delta and Wye.

Any help appreciated (this is driving me nuts - keep doing research but all the stuff gives me so much electro-babble my mind can't process any of it).

[BrianG]

Well, I would read the following links:

Info about general BL DC motors: Brushless DC Motors

Info about some of the math (but not necessarily about BL motors): Three Phase Info

AFAIK, the LMT motors are all rated by the Delta configurations.

Simplified: If you look at the Delta part of the attached pic, you'll see that when voltage is applied to nodes Z and X, current will flow through Ra. In the Y config, you see that applying voltage to the Z and X nodes requires current to pass through R3 and R1 in series. So, current will be less. Also, the series coils increases the turns, so kv will be less as well.

However, it's not quite that simple. The fact that there is AC going through each coil 120* out of phase with each other produces some current vectors. It's not like you have voltage on one node and ground on the other two nodes, so it gets a little confusing.

Incidentally, in three-phase industrial electrical AC applications, the Y pic could be a 3-phase transformer with the outer nodes being the power outputs while the center node would be the neutral connection.

[BP-Revo]

So...which provides more or less KV now? LOL My brain just can't take this... (PS. I've read both those articles before and only every 4 or 5 words makes sense to me :p - I've also read like 10 more different articles).

Wait I think I just got it - Wye has 1.73 times less KV right? If this is right - WOHOO! :D

[BrianG]

I think he's got it! :)

It can be confusing. A real expert might be able to shed more light on this...

[BP-Revo]

My brain still hurts - but I understand! I guess this is the price for understanding confusing concepts lol

[Serum]

I can understand it's pretty hard to understand;

Okay, here are the facts;

wye is also called Star , which is pretty obvious when looking at the diagramm

-Delta gives 1.73 MORE rpm on the same voltage than Wye
-Delta gives 1.73 LESS torque on the same voltage than Wye

[jhautz]

I know this rule is correct for Lehner motors, but its not the same for all brushless motors is it?

Example:

Neu 1512 2Y = 1400kv
Neu 1512 2D = 2600kv

1400*1.73=2422 not 2600

The math doesnt seem to work for Neu motors. Or am I mising something?


EDIT: The ratio seems to be more like 1.85 for Neu

[BP-Revo]

Maybe its just not 100% accurate? There has to be some other factors. .1 difference isn't huge, but its enough to raise an eyebrow.

[Serum]

nope, 1.73 it is. No way around it. It might be that certain winding techniques take more or less space. but then it would not exactly be a 2 winding.

Besides, the NEU motors have got pretty round KV values, don't you think?

[BP-Revo]

Yea...Neu KV values are always rounded off to a few spaces left of the decimal. Maybe they just slightly change the wind to accommodate? Or just round off KV figures as a close approximation?

KV figures cant be perfect, since they rely on ESC efficiency, etc.

[Serum]

Rubbish.

In the context you are using; KV values can be perfect, they don't rely on esc efficiency. it's the KV of a motor, not of a setup. This would include the esc efficiency, but the KV value doesn't imply that, this is 'just' efficiency. the KV number represents the number of RPM the motor makes on 1V, some companies measure the other way around; use the motor as a generator and watch at how many RPM the motor produces 1V, while some give the KV values loaded, others give them unloaded. (neu is unknown, but according to Mike, the numbers are loaded)

[BrianG]

A little off the subject:

[RANT]
I still have trouble with the whole "loaded" concept. Neu might rate their motors under a different load than LMT and so the numbers are skewed if you try to compare them. Personally, I'd rather have the unloaded value for all motors - at least the values would be consistently rated. I can always factor in 10-15% if speed is that critical.
[/RANT]

[Serum]

Agree, too bad there are different companies with different philosophies producing these motors Brian..

Arh, loaded/unloaded.. It just helps choosing a motor. this is where the software of Artur would come in handy (if all the motors are included)

[BP-Revo]

Yea the whole unloaded/loaded thing is a PITA.

[Serum]

i am happy that they provide this information.