Science, Physics, Math, & Myth

[John in CR]

Ok folks. Please try this out.

That one only opens excel for me, but no spreadsheet. Is it just my old crap puter acting up?

It's an ODF file. I'll save it as Excel for you.

It was opening those before directly to Excel. I must have said yes to a prompt in spanish that I shouldn't have, because now those I opened before come up blank too. arggh.

 

[Miles]

Anyway, try this:

 

[Arlo1]

Miles I'm sorry but I spun the motor with 60v on sine wave with sensorless and got 18.1818181818 rpm per volt I think this is more accurate. Can you edit the files?

Nissan claims a max rpm of 10300 running on 98s lithium charged to 4.1v a cell I think it is so they must use some field weakening.

 

[John in CR]

Anyway, try this:

While I expected the total drag torque to be lower, because these seem to coast better than other DD hubbies I've used, I was right to lack confidence in the breakdown, because the Eddy trq looks too much lower than those provided by Justin. It will be interesting once I get good numbers for no load current that prove the relationship at multiple rpm, and I think we should encourage anyone going to the trouble of gathering full data to include no-load at 3 different rpm as a good double check. It looks like I should also add another digit to my measurements.

Something I find very interesting is that starting with good measurements of a raw motor, using a simple measurement of no-load current and rpm at 2 points that we'll be able to evaluate reduction systems with accuracy. We talk about different types of reductions having low losses, but a simple number anyone can measure quantifies it.

Too bad this thread is so loaded with garbage at the front end with people who should know better arguing about a simple point of fact, because it's evolved into very interesting and useful info. Look how long it took for me to finally latch onto the concept that Kv gives us torque per amp, Kt. Then no load current tells us iron losses, and a simple measurement of phase-to-phase resistance and current gives us copper heat. While these topics have been touched upon in various threads, they've never been grouped together and put into simple form before. I'm sure guys like Miles and Justin have tried before, but they're often buried in topics over my head, so my eyes were too glazed over for the simple yet import concepts to take root. I've learned more and come to more eye opening realization in the past few weeks than my entire time on ES.

 

[Arlo1]

I think I got it... Lets try this.

 

[Miles]

Updated with Arlo1's revised data.

 

[Miles]

because the Eddy trq looks too much lower than those provided by Justin.

Possibly because Justin's figures are still per rad/sec (that's why they're in italics) and I changed the units for the column to rpm I'll convert to avoid any future confusion.

Bear in mind your lower pole count, too.....

 

[Martin A]

Kv gives us torque per amp, Kt. Then no load current tells us iron losses, and a simple measurement of phase-to-phase resistance and current gives us copper heat. While these topics have been touched upon in various threads, they've never been grouped together and put into simple form before.

How about a thread about concepts such as these in the main technical page?

 

[teslanv]

Too bad this thread is so loaded with garbage at the front end with people who should know better arguing about a simple point of fact, because it's evolved into very interesting and useful info. Look how long it took for me to finally latch onto the concept that Kv gives us torque per amp, Kt. Then no load current tells us iron losses, and a simple measurement of phase-to-phase resistance and current gives us copper heat. While these topics have been touched upon in various threads, they've never been grouped together and put into simple form before. I'm sure guys like Miles and Justin have tried before, but they're often buried in topics over my head, so my eyes were too glazed over for the simple yet import concepts to take root. I've learned more and come to more eye opening realization in the past few weeks than my entire time on ES.

Kingfish lives a stone's throw away from me, and we see each other often. He challenges me to look beyond what I "know", and to truly understand things. Likewise, I have often encouraged him to take a less adversarial approach. However, I would say that KF takes a special kind of pleasure with arguments such as these. It is his fuel.

You can call his writing garbage if you like. It doesn't both him a bit, although it does bother me, because I understand his end goals are ultimately to push advancement of EV technology. I can look past the rhetoric, accusations and name-calling and gain a better understanding, and I don't take offense simply because I do not yet have an ego to be bruised. I'm still a baby in this EV thing.

Regardless of how some feel this thread started, I believe ranks among the top threads as far as opening eyes to a better understanding of how motor performance should be judged. Kingfish made us all question what we think we already know. This is not a bad thing.

 

[Arlo1]

Updated with Arlo1's revised data.

Thanks. Now with .525NM/Amp for my motor is this a RMS amp value Or calculated from peak amps?

And does anyone know what the math is for copper saturation. How many amps can I flow through copper of 2awg or 4awg for 5 seconds or 10 seconds or 1 second....?

 

[Miles]

Updated with Arlo1's revised data.

Thanks. Now with .525NM/Amp for my motor is this a RMS amp value Or calculated from peak amps?

And does anyone know what the math is for copper saturation. How many amps can I flow through copper of 2awg or 4awg for 5 seconds or 10 seconds or 1 second....?

How did you measure the voltage for Ke?

AFAIK, copper doesn't saturate... It just gets hotter...

 

[speedmd]

Hi Arlo

Chart shows some fusing times vs amps. Your 2awg is good for some 1300 amps for tens seconds before it burns up. 9700 amps for 1 second. LOL
I would think you would want to look at max temp rise for wire insulation stability.

 

[John in CR]

Too bad this thread is so loaded with garbage at the front end with people who should know better arguing about a simple point of fact, because it's evolved into very interesting and useful info. Look how long it took for me to finally latch onto the concept that Kv gives us torque per amp, Kt. Then no load current tells us iron losses, and a simple measurement of phase-to-phase resistance and current gives us copper heat. While these topics have been touched upon in various threads, they've never been grouped together and put into simple form before. I'm sure guys like Miles and Justin have tried before, but they're often buried in topics over my head, so my eyes were too glazed over for the simple yet import concepts to take root. I've learned more and come to more eye opening realization in the past few weeks than my entire time on ES.

Kingfish lives a stone's throw away from me, and we see each other often. He challenges me to look beyond what I "know", and to truly understand things. Likewise, I have often encouraged him to take a less adversarial approach. However, I would say that KF takes a special kind of pleasure with arguments such as these. It is his fuel.

You can call his writing garbage if you like. It doesn't both him a bit, although it does bother me, because I understand his end goals are ultimately to push advancement of EV technology. I can look past the rhetoric, accusations and name-calling and gain a better understanding, and I don't take offense simply because I do not yet have an ego to be bruised. I'm still a baby in this EV thing.

Regardless of how some feel this thread started, I believe ranks among the top threads as far as opening eyes to a better understanding of how motor performance should be judged. Kingfish made us all question what we think we already know. This is not a bad thing.

BS, he gets credit for pissing me off enough to refuse to give him a pass. Anything more is to insinuate that his lack of understanding of such a basic concept was faked, and that's hilarious. "Fuel" for what, to pull out the Credentials Card and rattle off correct formulas, but not ones that support his position? He tried that on me before will similar results, and my suggestion from back then still stands. ie He should demand a refund of his tuition.

We were very lucky for the thread to evolve as it did, but I suppose you think KF had some role in that too despite not a single post.

 

[Arlo1]

Thanks guys at 2500 amps I need it to last 5-7 seconds. Not sure the awg of the windings or the wire into the motor but I will try to figure that out tonight.

 

[speedmd]

You will not be able to do that with normal plastic wire insulation. 2/0 is good for 2300 amps, 3/0-2700 amps for ten seconds before they evaporate in a poof of smoke going by the chart. You will need some high temp wire insulation or go bus style with some heat sinking.

 

[liveforphysics]

You will not be able to do that with normal plastic wire insulation. 2/0 is good for 2300 amps, 3/0-2700 amps for ten seconds before they evaporate in a poof of smoke going by the chart. You will need some high temp wire insulation or go bus style with some heat sinking.

That fusing current chart seems to be on the extremely conservative side of things. My own test experience (which I can repeat on video if you like) shows cables not fusing nearly so rapidly at those current levels. I think it's worth looking into the test process for collecting the fusing currents, my hunch is maybe that the test it conducted while the cable is already at maximum temperatures or something.

 

[Punx0r]

And presumably in free air, whereas a motor winding would (hopefully) have some conduction cooling.

Would it worth separating the later part of this thread into a new one dedicated to the motor data topic? Links to the truncated halves could be put in each thread to retain any context.

 

[amberwolf]

Would it make much of a difference if the cabling is exposed to air on all sides, vs bundled up together as it normally would be on a vehicle?

 

[liveforphysics]

Kingfish made us all question what we think we already know. This is not a bad thing.

After pages of explaining the obvious to him, he finally questioned what HE thought he knew, and in finding he had been obnoxiously preaching incorrect BS to people for years, he chose to stop participating rather than apologize.

That said, he isn't a bad guy and he is a huge EV fan and generally well-meaning. The issue he was mistaken on isn't immediately self-intuitive, and I once used to make the same arguments before Miles was kind enough to straight me out (which required swallowing my pride and knocking my ego down enough to learn something.)

Ego is the source of suffering and misunderstanding and delusion and spreading ignorance and pride etc. Should KF choose to overcome his ego at some point and return, I have no beef with him, and I certainly can't judge as I was no better just a few years ago.

Beyond anything drama related from this thread, it has provided mass awareness of electro-mechanical device basics for hundreds if not thousands of folks already. This awareness provides liberation from incorrect notions, and will lead to safer and simpler more robust higher efficiency drive choices for all ES'ers moving forward. That is a beautiful thing, we should be thankful for KF playing the roll of the perfect debate partner for dispelling the motor myths.

 

[Miles]

Would it worth separating the later part of this thread into a new one dedicated to the motor data topic? Links to the truncated halves could be put in each thread to retain any context.

I'm not sure. There is a reasonable break point here: http://endless-sphere.com/forums/viewtopic.php?p=980223#p980223

What's the consensus?

 

[Miles]

Something that we really need to give attention to is the relationship between:

DC voltage
Direct current
Peak to peak voltage
Peak voltage
RMS voltage
Peak current
RMS current
Block commutation
Sine commutation
speed
torque
Kv
Kt

 

[John in CR]

Would it worth separating the later part of this thread into a new one dedicated to the motor data topic? Links to the truncated halves could be put in each thread to retain any context.

I'm not sure. There is a reasonable break point here: http://endless-sphere.com/forums/viewtopic.php?p=980223#p980223

What's the consensus?

My attitude is if it ain't broke don't fix it, so I wouldn't want to do anything to make it die off. I'll stop throwing the sucker punches, and I apologize for not passing on the chance above. KF came up with a good thread title that may be what attracted you guys in the first place. I'm more interested in a summary once this thread has run it's course, plus maybe several threads with very descriptive titles and a first post containing accurate and complete info, without turning into a book like is my tendency. Each of those would include a link to your master spreadsheet that hopefully will turn into a comprehensive motor database. I don't know how or what is needed to work heat dissipation in, but imagine what an army of ESers with an understanding of the items in your spreadsheet that links to a simulator could accomplish.

 

[John in CR]

Something that we really need to give attention to is the relationship between:

DC voltage
Direct current
Peak to peak voltage
Peak voltage
RMS voltage
Peak current
RMS current
Block commutation
Sine commutation
speed
torque
Kv
Kt

Goody, lot's more to learn. Please start the ball rolling with how those different voltages relate and what they should mean to us.

 

[Miles]

Tidied a few things up, including converting Justin's Eddy current torque values from Nm/Rad/Sec to Nm/rpm

 

[teslanv]

I'd love to see Death Bike's Motor in this database...