computer program used to sculpt Electric motor design

[hal2000]

Found this research, and thought it might inspire some of the members to share their ideas for motor design improvements that go beyond oil filling, rewinding, or drilling holes in hubbies. Ok ill go first .....after I finish wading through the reams if info on motor design on E.S. to find out how many more of my ideas are old news. Ok Ok I wondered if using two wire gauges and turn numbers, on different areas of the same stator would let you create a motor that is two- in-one, speed wind and and torque wind, Instead of using gears.) CR'S motors do this, right? So Why is this idea not used much? Oh here's the link
[/url] http://www.sciencedaily.com/releases/2012/01/120126123105.htm.

 

[amberwolf]

I wondered if using two wire gauges and turn numbers, on different areas of the same stator would let you create a motor that is two- in-one, speed wind and and torque wind, Instead of using gears.)

You mean like a cieling fan motor commonly does? One winding on the outer part of the stator teeth, and another on the inner?

 

[jonescg]

Wouldn't that effectively mean your motor is always going to be half as powerful for it's mass?

 

[Miles]

I wondered if using two wire gauges and turn numbers, on different areas of the same stator would let you create a motor that is two- in-one, speed wind and and torque wind, Instead of using gears.)

Crystalyte made a hub motor with a tapped winding, years ago. Not surprisingly, it didn't have much success...

There is no such thing as a high torque wind. Motors are limited by efficiency and heat dissipation which are not related to Kv/Kt. As soon as you use less than 100% of the copper you reduce efficiency - parasitic losses will remain the same.

 

[hal2000]

Is there no such thing as a high torque wind, because torque is affected by the stator radius (leverage) for a given strength of flux field, magnet interaction? If there is no such thing as a high torque wind, why do members here call some winds (speed winds) when rewinding stators. I'm sure I have read members who refer to two versions of a motor offered by a manufacturer both with the same physical dimensions. with one being better for hills, isn't that a motor that was wound for high torque at a lower speed?

 

[hal2000]

aren't the motors john in CR is working on an example of a high torque wind and a high speed wind on alternating teeth of the same stator, sort of two motors in one?

 

[Miles]

Is there no such thing as a high torque wind, because torque is affected by the stator radius (leverage) for a given strength of flux field, magnet interaction? If there is no such thing as a high torque wind, why do members here call some winds (speed winds) when rewinding stators. I'm sure I have read members who refer to two versions of a motor offered by a manufacturer both with the same physical dimensions. with one being better for hills, isn't that a motor that was wound for high torque at a lower speed?

The number of winding turns controls the speed and torque constants. A greater number of turns will reduce the speed constant and increase the torque constant. So, you will get more torque per unit of current. The amount of heat generated per unit of torque will remain the same, however, as increasing the number of turns increases the resistance.

Yes, it's common to see references to "torque" and "speed" winds but, as you've proved, it just confuses things. Delta/Wye switching, tapped or dual windings, parallel/series switching are just not substitutes for mechanical gearing.

Sometimes the fill factor will vary slightly for different winds of the same motor, this will affect efficiency.

 

[Miles]

"Slower" winds of hub motor may be better for hill climbing but, if that's so, let's find the right reason for that...

How much does the duty cycle affect efficiency? etc. etc.

 

[liveforphysics]

Is there no such thingy as a high torque wind, because torque is affected by the stator radius (leverage) for a given strength of flux field, magnet interaction? If there is no such thing as a high torque wind, why do members here call some winds (speed winds) when rewinding stators. I'm sure I have read members who refer to two versions of a motor offered by a manufacturer both with the same physical dimensions. with one being better for hills, isn't that a motor that was wound for high torque at a lower speed?

There are high speed winds, as in the kv is high so they are capable turning fast for a given voltage.
The high speed winds are capable of the exact same torque as the lower kv motors, they just require more phase current from the controller to do it, this doesnt mean they draw a bit more current from the battery, just added stress to the controller.

If we all had controllers with magic fets that had 10uOhm RdsOn, and no ESR caps, we would all be running 1 turn motors.

 

[Farfle]

Hmm, asymmetrical stator teeth... could be interesting.

 

[John in CR]

aren't the motors john in CR is working on an example of a high torque wind and a high speed wind on alternating teeth of the same stator, sort of two motors in one?

No. You are combining info about 2 different motors.

One has series/parallel switching. I'm unsure of the strand count, but let's say it's 10 strands of wire for each of the 3 phases, and they are wrapped 6 times around each tooth. The 10 strands are split into 5 and 5. When the pair of 5 strand bundles are terminated in parallel, then it's a 6 turn motor with a total of 60 strands of wire wrapped around each tooth. That is the high speed mode. When the pair of bundles is connected in series, then it is a 12 turn motor (a bundle of 5 wrapped 12 times) still with a total of 60 strands of wire around each tooth. That is the slow setting, so the motor's efficiency and power curves are shifted to a lower rpm. That setting is good for going slow, or to climb hills more slowly, or to use during take off, all because the motor is more efficient at low rpms in this mode. All copper is always in use whichever mode the motor is in.

The other is essentially 2 motors on one stator. On the Enertrak dual hub, their stators are side by side sharing a common axle. With the motors I have, they are wound on alternating teeth of the same stator. Either system requires 2 controllers to get all the copper working.

 

[John in CR]

If we all had controllers with magic fets that had 10uOhm RdsOn, and no ESR caps, we would all be running 1 turn motors.

I've got one with 1.5 turns, and that controller lives on the borderline of plasma every time I hit the throttle. I with that motor had better lams so it could go to higher rpm.

 

[John in CR]

"Slower" winds of hub motor may be better for hill climbing but, if that's so, let's find the right reason for that...

They're better at climbing them more slowly. Slower requires less power, and a slower wound motor is more efficient at lower rpm.

That's for guys who want to go slower on hills like in off-road riding, or whose whimpy motors can't produce enough power to go up the hill at the higher speed they'd like to climb it.

I agree that the changes in windings aren't a substitute for a gearing change, but if you're a bit shy on power or just want to go slower, then they work well. Unfortunately those who tried switching in the past thought they'd get a big torque difference but were sorely disappointed, and they missed the real benefit, which is hill climbing or just stuck in stop and go traffic with no chain for your legs to help those low speed starts.

Since we don't have any trannies up to the task, then I'd argue there's no substitute for raw power, so you can blast right up those hills. Heavy stop and go traffic is still a problem though.

John

 

[Miles]

They're better at climbing them more slowly. Slower requires less power, and a slower wound motor is more efficient at lower rpm.

If it is. Why?
Efficiency is supposedly in a fixed relationship to torque. Parasitic losses are a neutral. Duty cycle is the only difference. No?

 

[Toorbough ULL-Zeveigh]

If there is no such thing as a high torque wind, why do members here call some winds (speed winds) when rewinding stators.

it's all joshua goldberg's fault.
don't think it started over at the power-assist yahoo group but fer sure it's where it blew up.
some EE made the (stress) analogy to some noob's question regarding the difference in windings.
ever after goldblurb just ran with it until it took on a life of it's own reaching "nicad-memory" urban legend status.
hope this helps.
if you're still amongst the living

 

[john61ct]

8 year-old zombie thread

 

[Toorbough ULL-Zeveigh]

yes, i knows capn' obvious
that's what it takes to address history
trying to drive a stake thru the heart of the speed/torque wind urban legend

 

[Dauntless]

yes, i knows capn' obvious
that's what it takes to address history
trying to drive a stake thru the heart of the speed/torque wind urban legend

Jawohl, Admiral.

 

[spinningmagnets]

I dont have the need for a 2-speed transmission, but since brushless motors are so easily reversible, I feel that Miles' work in the 2-speed retro-direct transmission is brilliant stuff.

Once built and added to a non-hub motor system, the transmission should last your lifetime. I could see me making one if I owned a pedicab at the beach...