18x4 22x3 29x2 etc winding, BUT WHAT ABOUT STRANDS SIZE !!

[Doctorbass]

People are more and more informed about type/configuration of motor winding... and we all know that the copper fill is expressed as a number of parallel strands time a number of TURNS.....

But to me... there is something we are missing!!.. WHY NOBODY CARE about the STRANDS SIZE ??

Guys...I am not 100% sure that every motor are all using the same size size of strands!! so why not take that into account when comparing copper fill ?

Why we only care about parallel and turns ?? :| if what matter is the copper fill ( total cross sectional of copper per tooth) and that the size of teh strands also determine that?

Doc

 

[voicecoils]

It's a simplification.

For the end user, strands and turns could be ignored in deciding which winding motor to run given the following info:

* rpm/volt (Kv)
* weight of copper windings (grams)

This way you can choose the winding variant to match your required speed (if battery voltage is inflexible) or you could simply choose the motor winding that has the most copper mass (and therefore likely greatest copper fill).

 

[Punx0r]

My understanding is that within the winding options of a particular model of motor they are all wound with the same wire, so the only variables are strand number and turn count.

 

[Drunkskunk]

I would assume that all motors within a specified line would have the same gauge wire in the strands. It just makes sense from a cost and inventory standpoint. having only 1 gauge wire in all the motors simplifies all of the inventory stocking and material ordering processes. Also, if you have only 1 gauge, you're buying more of that gauge, so you may be getting a bulk rate discount, lowering your production costs.


I'd love to know what gauge goes into any motor I buy. I'd also like to know what thickness laminations they are using, and what class of magnets they are using.

 

[John in CR]

The numbers to get are phase-to-phase resistance and Kv at a minimum. Then strand size doesn't matter and you know the torque per amp too, and you can't get screwed by cheap quality of magnet wire, which has a higher resistance for a given gauge. No load current at a specific rpm is good info about iron losses, but if you can get no-load current at 2 different rpm, then it's possible to get the breakdown of eddy current and hysteresis losses (one plateaus and the other continues to increase with rpm) for good predictive data about iron losses.

Add physical dimensions of the stator and whole motor and that's all the info needed for the full compliment of data on Miles' spreadsheet. Until we pull together and get the data for all of the motors we use into his spreadsheet, motor performance is just anecdotes and fables.

 

[cwah]

Is there somewhere I can learn about how a motor work for newbie? Without all these equation or symbols?

 

[liveforphysics]

There is a unit called Km that describes what you're trying to express. It's a clever unit, a measure of the amount of restive loss heat produced per unit of torque a motor makes.

http://www.motioncomp.com/pdfs/Motor_Constant_Great_Equalizer.pdf

 

[Doctorbass]

There is a unit called Km that describes what you're trying to express. It's a clever unit, a measure of the amount of restive loss heat produced per unit of torque a motor makes.

http://www.motioncomp.com/pdfs/Motor_Constant_Great_Equalizer.pdf

Great Find Luke!, if only we could have these data for every availlable popular hub motor! wer could compare apple with apple!

Doc

 

[John in CR]

There is a unit called Km that describes what you're trying to express. It's a clever unit, a measure of the amount of restive loss heat produced per unit of torque a motor makes.

http://www.motioncomp.com/pdfs/Motor_Constant_Great_Equalizer.pdf

Great Find Luke!, if only we could have these data for every availlable popular hub motor! wer could compare apple with apple!

Doc

It's all in Miles' spreadsheet, including Km. We just need to help him populate it. Look at Justin's posts in the Math and Physics thread in Ebike Technical for a good explanation of some of the computations, along with Miles' and Luke's introduction of Km. Personally I just need resistance and Kv to compare current handling and torque when comparing motors, and the iron loss side to evaluate the voltage limits, and the combination lets me know the power. Km works best for a comparison of similar motors, rather than being the "great equalizer that motioncomp claims. Maybe I'm missing something, since Luke likes it so much.

 

[madin88]

regarding Km constant: when do we talk about "similar" motors?

here is a good example:

QS 205 / 50 V2 stator type: 51 teeth, 23 pole pairs, 18 x 4turns
QS 205 / 50 V3 stator type: 36 teeth, 16 pole pairs, 24 x 5turns

they have similar stator diamter and similar magnet width.

btw:
many of these hub motors use strands with 0,5mm diamter which results in a cross section of 0,196mm².
we also could ask the manufacturer about total cross section and than divide it by number of strands..

 

[John in CR]

regarding Km constant: when do we talk about "similar" motors?

here is a good example:

QS 205 / 50 V2 stator type: 51 teeth, 23 pole pairs, 18 x 4turns
QS 205 / 50 V3 stator type: 36 teeth, 16 pole pairs, 24 x 5turns

they have similar stator diamter and similar magnet width.

btw:
many of these hub motors use strands with 0,5mm diamter which results in a cross section of 0,196mm².
we also could ask the manufacturer about total cross section and than divide it by number of strands..

What did you want to discuss? We really need phase-to-phase resistance and Kv to properly discuss the differences. No-load current (ideally at 2 different rpm or WOT at 2 voltages) would be quite helpful too.

In general, with the same magnet working area at the same radius, they will be capable of the same maximum torque, but it's a bad idea to get even close to those current levels unless it's a drag race. Reducing the poll count reduces the operating frequency at a given rpm, so assuming the same stator steel it would increase efficiency (and decrease heat) by reducing iron losses. You end up with shorter thicker copper (despite the greater turns on each tooth) for a given Kv, so that decreases copper losses for a given current and increases power handling. The reason it's not common for Chinese hubbies to take advantage in this regard is that it requires more copper and more stator steel, the expensive materials in hubbies. Instead they went for low cost, so bigger diameters and high slot and pole counts, so they can use small amounts of stator steel and copper.

 

[teslanv]

We really need phase-to-phase resistance and Kv to properly discuss the differences.

Reported Here for the MXUS 3000W Motors:

http://endless-sphere.com/forums/viewtopic.php?f=2&t=67357&start=25#p1021941

 

[madin88]

The reason it's not common for Chinese hubbies to take advantage in this regard is that it requires more copper and more stator steel, the expensive materials in hubbies. Instead they went for low cost, so bigger diameters and high slot and pole counts, so they can use small amounts of stator steel and copper.

Are you sure its ONLY about costs?
AFAIK more stator teeth or higher pole count has advantages regarding torque. thus i think QS V2 has higher kT than QS V3 (if we talking about same kV), but thats only a guess..

 

[John in CR]

The reason it's not common for Chinese hubbies to take advantage in this regard is that it requires more copper and more stator steel, the expensive materials in hubbies. Instead they went for low cost, so bigger diameters and high slot and pole counts, so they can use small amounts of stator steel and copper.

Are you sure its ONLY about costs?
AFAIK more stator teeth or higher pole count has advantages regarding torque. thus i think QS V2 has higher kT than QS V3 (if we talking about same kV), but thats only a guess..

Cost and weight. Increasing slots and poles does nothing regarding torque. Torque limits are basically set by the magnetic working area and it's radius. Our HubMonster motors have only 20 magnets (10 pole pairs) and 24 slots (12 teeth for each set of 3 phases, and they embarrass any hubmotor of 15kg or less despite the handicap of having a smaller stator diameter. Fewer slots means more turns for the same Kv, which for a given power handling (thickness of copper) that means more space behind each slot to fit the windings and more stator steel behind the root of the teeth. That combines for more of the expensive stator steel. Common hubbies have what is like ribbons of stator steel and copper compared to HubMonster, MidMonster, and MiniMonster. The higher quality steel, lower slot and pole count, and extra thick copper for low phase resistance are what combine to make them significantly more efficient that all hubmotors other than the $10k handmade to order CSIRO 1kw hubbie used for solar challenge vehicles.