Science, Physics, Math, & Myth

[John in CR]

Adding to LFP's post, our motors see only phase current, something we can't measure, and it's the difference in phase current vs the Kt (Kt in Nm/amp = 9.5478/Kv in rpm/volt) that determines the difference in torque. Controllers deliver very different phase current based on the motor load and rpm, so when you use the same controller to compare 2 different windings the results are very close to the same at low rpm as shown by Justin.

 

[Arlo1]

Adding to LFP's post, our motors see only phase current, something we can't measure, and it's the difference in phase current vs the Kt (Kt in Nm/amp = 9.5478/Kv in rpm/volt) that determines the difference in torque. Controllers deliver very different phase current based on the motor load and rpm, so when you use the same controller to compare 2 different windings the results are very close to the same at low rpm as shown by Justin.

uhm,,,, My controller measures phase current....
Most GOOD controllers do and that's how they give you buttery smooth throttle as well as one of the ways to protect the power
switches.

 

[zombiess]

It takes me about 7 grand of labor to fully engineer a motor from nothing. Power engineers have told me 2000 hours into a 100% new controller design is not out of the ordinary, and at the base rate of $35 an hour to hire a smart and fresh power engineering grad thats right at $70,000 without taxes and benefits. Contract labor for power engineering in the US can be anywhere from $120 to $400 an hour.

I think this is fairly realistic. I had a highly skilled tutor who taught me the basics of power electronics and I already had +25yrs of above average hobbyist level back ground. It's no small task to build a +10kW capable power stage. I'm trying to learn the control theory part now for some other work I'm doing and would eventually be interested in rolling my own controller, but the learning task is a huge undertaking. I've been going at for 3/4 months now and I'm just now getting things to click into place and make more sense (tons of info to digest). The actual programming of a DSP to do the control is actually not that difficult, it's figuring out to to control the motor and making the power stage robust.

I'm not sure about the salary as jobs I looked at for experience EE's with power electronics topped at at only 120k with an average around 100k/yr. Of course contract work would pay more and someone at the top of their game with a background in a demanding environment such as aerospace could probably command a tidy sum.

My first controller probably has 1500 hours into it since it took me nearly a year working nights/weekends to get it to where it is (still needs more testing for a power rating). The 2nd design (still to be tested once I'm not sick) went much quicker.

 

[Arlo1]

Some more leaf motor data. The motor it self weighs 120.6 lbs with no wires run out of it. I weighed it.
With about 110v It spun 2195 rpm with 2.38 amps and with 205v at 4306 rpm I got 3.42 amps
Also measured 21rpm per volt at 205v under load it give me 4306 rpm.

So it looks like it would be about 5.535amps at 8600 rpm. From my best guess.... It looks like there is a waste of 1.3 amps in something at every rpm....
I will get this data when I can. The lams are uber thin so I don't think eddy currents will be much of a load until over 10k

 

[John in CR]

Out of curiosity what was the phase current at 4306rpm?

 

[Arlo1]

Out of curiosity what was the phase current at 4306rpm?

I was unloaded. So was very small but it was set to 120 for acceleration. I can hook my scope up to one of the sensors and show you if you think I need to....

 

[John in CR]

Out of curiosity what was the phase current at 4306rpm?

I was unloaded. So was very small but it was set to 120 for acceleration. I can hook my scope up to one of the sensors and show you if you think I need to....

You said today's "good" controllers measure phase current, so I asked what the phase current was. While they may know the phase current for the controllers' operation, they still don't tell you the phase current, so I'll add "easily" to my previous statement and say that we can't easily measure phase current for making a straight forward comparison of 2 different windings of the same motor.

 

[Arlo1]

Out of curiosity what was the phase current at 4306rpm?

I was unloaded. So was very small but it was set to 120 for acceleration. I can hook my scope up to one of the sensors and show you if you think I need to....

You said today's "good" controllers measure phase current, so I asked what the phase current was. While they may know the phase current for the controllers' operation, they still don't tell you the phase current, so I'll add "easily" to my previous statement and say that we can't easily measure phase current for making a straight forward comparison of 2 different windings of the same motor.

Is this "easily" enough for you?
[youtube]IyS5QMAmRvE[/youtube]

 

[Doctorbass]

Want popcorn?

This is my tour John

No kidding... The tests you do Arlo are very interesting good luck for your project :wink:

Doc

 

[Arlo1]

Want popcorn?

This is my tour John

No kidding... The tests you do Arlo are very interesting good luck for your project :wink:

Doc

Thanks. I try to get data as accurate as I can but sometimes it takes a while for me to learn what others already know. Non the less I putt effort into being as accurate as I can on very tight a budget.

Ryan Commented on my Video.

On the zero dash (2014 and newer) there is a power meter, which is based off battery amps and volts, and a torque meter based off the motor Iq (AC phase torque producing current) as reported from the motor controller.

So it does point out there is a little use to knowing the phase current on the fly as it will readout in terms of torque.

 

[ferret]

A question for the motor gurus in this thread:

I'm trying to compare the following 3 motors for a build:
Astro 3210 10 turn (135 KV) with 1:16 reduction
Astro 3220 5 turn (135 KV) with 1:16 reduction
Astro 3220 10 turn (68 KV) with 1:8 reduction

According to my calculations, inputting 50V limited to 100A phase current, all three motors will give a maximal speed of about 50 kph and maximal torque at the wheel of 8000 in oz.

After reading the thread I came to these conclusions:
The three motors will give identical performance and place the same loads on the battery and controller.
The 3210 will be less efficient than the 3220s because it has a lower KM.
The 3220 10 turn will get twice as hot because it will need to make twice the the torque to get the same torque at the wheel. It will also be quieter because it will be running at half the RPM.

Are my conclusions correct?
Anything else I'm missing that will effect the motor choice?

Thanks,
Avner.

 

[ferret]

One thong that I don't understand is why is the heat produced is a function of the torque the motor produces.
I always thought that it a function of the power produced and the efficiency.

Can anyone explain?

Avner.

 

[Arlo1]

One thong that I don't understand is why is the heat produced is a function of the torque the motor produces.
I always thought that it a function of the power produced and the efficiency.

Can anyone explain?

Avner.

because the amps flowing through the motor (phase amps) is what controls the heat but is also what controls the torque.
2x the phase amps = 2x the torque (minus increasing efficiency losses) and also = 2x the heat (plus increasing efficiency losses.)

 

[John in CR]

A question for the motor gurus in this thread:

I'm trying to compare the following 3 motors for a build:
Astro 3210 10 turn (135 KV) with 1:16 reduction
Astro 3220 5 turn (135 KV) with 1:16 reduction
Astro 3220 10 turn (68 KV) with 1:8 reduction

According to my calculations, inputting 50V limited to 100A phase current, all three motors will give a maximal speed of about 50 kph and maximal torque at the wheel of 8000 in oz.

After reading the thread I came to these conclusions:
The three motors will give identical performance and place the same loads on the battery and controller.
The 3210 will be less efficient than the 3220s because it has a lower KM.
The 3220 10 turn will get twice as hot because it will need to make twice the the torque to get the same torque at the wheel. It will also be quieter because it will be running at half the RPM.

Are my conclusions correct?
Anything else I'm missing that will effect the motor choice?

Thanks,
Avner.

Avner,

I don't know the difference between the 3210 and the 3220, but the 2 3220's are effectively the same motor and you simply run them at different voltages and current for the same result. ie Run the 10turn at 100V 50A with the same gear reduction and it will have identical performance as the 5 turn run at 50V 100A, same rpm, same torque, same heat. If you try to run the two 3220's at the same voltage and current, the 10 turn will spin half as fast and make 4 times the heat in the copper due to 4 times the resistance (twice as long copper strands and half as many) and it will have less heat created in the iron (somewhat more than 1/2) because it is rpm based with a mostly fixed portion and a mostly linear portion.

 

[John in CR]

because the amps flowing through the motor (phase amps) is what controls the heat but is also what controls the torque.
2x the phase amps = 2x the torque (minus increasing efficiency losses) and also = 2x the heat (plus increasing efficiency losses.)

??? "minus increasing efficiency losses" and "plus increasing efficiency losses"...???

2x the phase amps = 2x the torque...period, unless you are into saturation where increasing current has diminishing returns up to full saturation where no more torque is created.

2x the phase amps = 4x the heat...period. Copper losses is current squared times resistance. Copper losses also increase with temperature, because resistance increases with temperature, but that's outside of the discussion point.

Who's lazy and ignorant? You've got some nerve posting that stupid video.

 

[John in CR]

Want popcorn?

This is my tour John

WTF are you talking about?

 

[Arlo1]

because the amps flowing through the motor (phase amps) is what controls the heat but is also what controls the torque.
2x the phase amps = 2x the torque (minus increasing efficiency losses) and also = 2x the heat (plus increasing efficiency losses.)

??? "minus increasing efficiency losses" and "plus increasing efficiency losses"...??? If you re-read this you will understand what I said as in 2x the current is not perfectly 2x the torque it will have a little less then 2x the torque as the losses will increase as well

2x the phase amps = 2x the torque...period, unless you are into saturation where increasing current has diminishing returns up to full saturation where no more torque is created.

2x the phase amps = 4x the heat...period. Copper losses is current squared times resistance. Copper losses also increase with temperature, because resistance increases with temperature, but that's outside of the discussion point.You got me here but that is some of what I was saying about the losses increasing as the current does.

Who's lazy and ignorant? You've got some nerve posting that stupid video.

What did you expect? You have a hate on for controllers with the more advanced features and tried to rub something in my face not knowing I would be able to come though with something you didn't know existed. You have arguments with more then a few who work hard on the forum and we all try to get accurate data, You had no need to ask for what the phase current of my controller is other then trying to be a dick!

 

[Doctorbass]

Want popcorn?

This is my tour John

WTF are you talking about?

see the other thread about field weakening that you commented and you will catch about the popcorn :wink:

John, please relax... 8) we all like ebikes period!

Arlo, About the heat that increase 4 times instead of 2 i think John is right for that but i know you probably just made a typo..

Doc

 

[ferret]

Thanks guys!

Going over your explanations and the motor data, I now understand that for the different motors same torque will create same heat (even though they will be drawing different currents) because the difference between their winding resistance is the same as the difference between their KT squared.

Avner.

 

[John in CR]

Going over your explanations and the motor data, I now understand that for the different motors same torque will create same heat (even though they will be drawing different currents)

That's true for the 3220's, because they are the same motor, just with copper wound in a different way, so which you choose is a matter of which voltage and current you want to run. To compare the 3210 to the 3220 I believe it's good that you compare them with the same Kv. That makes it easy, since Kt (torque per amp) is also the same. Compare phase-to-phase resistance to see the difference in copper losses. The other component of heat generated is iron losses, which you shouldn't ignore, since you're talking about a fast spinning motor. No-load current of each multiplied by your chosen voltage, tells you the maximum.

You can't automatically say that the 3220 will be more efficient, because which is more efficient will be load dependent. ie The 3220 has more iron and more iron losses to overcome, so at light loads such as a long flat commute at modest speed, the 3210 could quite possibly be more efficient overall if most of your time is spent at steady cruise where current demands are low and the reduced iron losses could be great enough to offset higher resistance in the copper. In more demanding use, then yes the 3220 is sure to be more efficient overall simply because it's more motor, so it runs at lower stress. Greater efficiency will show up in the form of much lower copper losses and only slightly higher iron losses. It's only the loss side of efficiency that will be different as long as the 3210 isn't pushed to saturation, because the power produced side is identical since the torque per amp (Kt) is the same and so is rpm per volt (Kv). I'm not sure a comparison of Km gives the same comparison, because Km hasn't fully sunk in for me.

John

 

[John in CR]

Doc and Arlo1, my Canadian brothers, I'll just let it slide and just chalk it up to it being too cold now up there now, because there's some miscommunication issues that I'm not getting dragged further into.

Arlo1, I've got nothing against features at all. In fact, the dirt cheap controllers I'm testing are quite packed with features...blue tooth smart phone communication for programming and on the fly data reporting, multiple throttle tuning criteria, and switch on the fly throttle presets along with a host of other goodies we should have had years ago. I'm sure the FOC controllers the factory is about to launch will have even more goodies, hopefully including your buttery smooth torque control at the throttle. I love features. It's high price per unit of power motor control systems that I'm dead set against, and unless those in the west change their tune in that regard, China's dominance WRT electric transportation will widen. I'm not talking about pushing the envelope Ferrari-like controllers like you've put so much effort into, because that will always be high priced. I'm talking about meat and potatoes driving an electric motor that every household should have type systems, so R&D costs need to be spread over 10,000 or 100,000 or more units, leaving a reasonably low price for a box of electronic bits that moderately skilled labor can assemble.

Regarding measurement and reporting of phase current, I suggest getting a better handle on the loss side for our motors, because having live phase current numbers sent to something like a CA would be an awesome thing for our bikes. That's just small easy steps from having live and average efficiency info data at our fingertips that would have an array of uses.

 

[Arlo1]

Ill edit the video later. Just wanted to make a point and I was frustrated.

Regarding measurement and reporting of phase current, I suggest getting a better handle on the loss side for our motors, because having live phase current numbers sent to something like a CA would be an awesome thing for our bikes. That's just small easy steps from having live and average efficiency info data at our fingertips that would have an array of uses.

Like I said ryan posted 2015 Zeros now read torque on the fly which is based on the phase amps.... So this stuff is happening.
Im building controllers because not much exsists at all for what I need and because I don't have the money for a 20,000 controller to make 300-400hp I want.
All said and done I will have ~1000 into the leaf inverter but I can't do that again as the deals on used parts are gone.... I can't stess enough what good caps/fets and engineering costs. The goal with Good controllers is to have them last 20 years pluss. If your cheeper controllers die every 5 years are you still saving money?

Controller prices will come down in time. I am trying to help that by doing it all open source. If some Chinese company can build what I did for less money I will order more from them

 

[arkmundi]

I just watched NOVA - Big Bang Machine, which aired January 14th 2015 on PBS (thanks to the Bittorrent community). I figured, why not right here in the Science, Physics, Math, & Myth thread? :lol: The Large Hadron Collider, the largest scientific experiment in our brief human history, was built to find the the Higgs boson. With an extraordinary scientific consensus, on July 4th 2012, the Higgs field was confirmed, garnering the 2013 Nobel Prize in Physics for François Englert and Peter Higgs. Well deserved!

On 4 July 2012, the discovery of a new particle with a mass between 125 and 127 GeV/c2 was announced; physicists suspected that it was the Higgs boson. By March 2013, the particle had been proven to behave, interact and decay in many of the ways predicted by the Standard Model

While all this is really exciting stuff, what I had not realized is that the Large Hadron Collider Upgrades Are Complete as Researchers Gear Up for 2015, with twice the particle colliding energy than before. What does this mean? We should amuse ourselves speculating:
[youtube]BMvT2sriq34[/youtube]

 

[teslanv]

Plotted the 9C Clone (28mm) DD Hub Motor Thrust Chart.

Max Phase currents are based on the ebikes.ca simulator for the 9C 2807 Motor for overheating in 4 minutes.

Looks like the clear winner here is the 8X8T winding in all tire sizes, since it has the highest copper fill.

 

[Hummina Shadeeba]

what i know is only the copper in the tooth does create a magnetic field and the copper on the left and right side does nothing..

Oh, it does indeed create a magnetic field, but since (most of?) the part of the field it creates isn't directly interacting with the magnets (at least in a direction useful to desired work), it's not useful to making torque and motion in the motor.

It could also cause eddy currents within the side covers of a hubmotor, if the field is strong enough and teh covers close enough to it, and that could generate additional heat and friction to actively negate some of the motor's motion, though I don't know how much that happens in practice.

I'm wondering how many.... or much.. eddy currents are going to be produced in a hub motor I'm making which has windings which I plan to have butted almost against it's side walls. One side will be aluminum and one side steel. I plan to stick a sheet of some electrical insulation between the windings and sides to make it safer but I'm also wondering if a sheet of Mu metal or something would block the field. Is heat a good simple indicator of eddy currents?

http://fms-corp.com/mitigation_shielding.php4