Getting Wound Up: Stranded vs Bar Windings in Electric Motors
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- Опубліковано 17 тра 2024
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New associate Paul explains the differences, pros, and cons of both stranded and bar windings in electric motors.
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#electricvehicle #motor #automotive - Авто та транспорт
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What language? *Klingon* 😊
Distracting add. Do you really need to do this?
@@jazzybeat28 how about you pay them for the content they publish for free so that they don't ever need to do another ad. You act like you can't simply skip that part...
@eat28 ads are fine if it is relevant to the topic or industry but this... it feels low like there is something wrong with Munro
Lucid has a better video on hair pin motors, Munro should have watched that and just regurgitated what is in there. Skin Effect from what I remember is only significant frequencies. Electric motors don't have high frequencies, frequencies are just around the RPMs of the motor. The one huge advantage of hair pin also was not mentioned here
Another EXCELLENT video aimed at the ‘semi-geek’ for EV technology. Thank you for making understanding THE priority.
Paul Turnbull is one heckuva good teacher. No wasted words.
Focuses on the important interesting facts & ideas.
Indeed
@@sillystuff6247 Thank you!
I heckin love soyence
I think this was one take. Impressive. Thank you for your service!
Thank you very much!
As a former physics teacher I think you gave an excellent explanation of what is going on inside of an electric motor. I especially liked the way you explained back EMF 👍
Thank you!
Twenty minutes well spent! Great video
Awesome, thank you!
2 things you don't mention about AC winding losses: first, the reduction to 1/3rd at skin depth, there is also a PHASE SHIFT in the current, being retarded about 60° at one skin depth, & this reduction in amplitude & phase shift continues as you move inward. But there is a second effect when a bunch of wires carrying current in the same direction are packed together. There is a loss which makes the resistance rise TO THE 4TH POWER OF THE FREQUENCY. This is because of the magnetic field in SURROUNDING conductors. Butterworth wrote about this in the 1930's as it applied to wound radio antennas, & showed that cheap radios, having antenna coils wound with thinner wire, actually performed better than the antennas in the expensive radios. I ran into this when working with Rockwell International making magnetic bubble memories in the 1980's, which have 2 quadrature driving coils (like 2-phase motor). Rockwell's coils used 1mm x 1mm square wire & had 3 times the loss of my 28-strand coils of the came cross-section.
Another thing about bar-wound coils. Most of the stock for these are made from existing round wire, rolled square AFTER INSULATING & heat-treating. The copper is overworked & this raises resistivity. The wire needs to be brought to the same state in cold-working as round wire, but manufacturers selling square wire don't do that. Does Tesla have enough "pull" to get manufacturers to properly heat-treat wire BEFORE insulating?
This comment is a great example of what I love about the Munro Live community. Thanks for sharing this great information. You will be happy to learn that the copper wire suppliers have responded to the dramatic increase in square wire demand from auto manufacturers (not just Tesla) by producing new square wire products.
Fascinating Comment.... Why not form the bar out of heat treated strands, by drawing the strands through a bar-shaped die? And if needed heat treat the entire bar again? And possibly with a lamination of the wires?
The metallurgical nature of the copper does seem to be a relatively important factor that wasn't focused on in the post?
wow super detailed insight. thanks
Excellent comment. I was thinking Litz wire, which is multi strand woven wire with individually insulated strands. New England Wire Company has been manufacturing Litz wire in the US since at least 1920. The oldest reference I know dates from 1898, so knowledge of skin effect is not new. Historically, motors have not had to resort to exotic stator winding wire because AC current was at most a few hundred Hz frequency. Radio engineers started winding coils in receiving sets and transmitters with Litz wire to help prevent losses in the coils. Keeping the effective resistance of the coil low improves Q, the sharpness of resonance, and helps reject adjacent stations. If you want to find some litz wire, it is sometimes used in transformers of switch mode power supplies of mobile phone chargers, etc. If you disassemble a wireless Qi phone charger, the coupling coil is often made with Litz wire.
If you read the Wikipedia article on Litz wire, the author mentions the antenna tuning coil of radio station WWVB, which operates at 60 KHz, has a 19 mm diameter conductor made of 6075 strands of #36 magnet wire. WWVB is the US time standard station which transmits signals to keep “atomic” wrist watches and wall clocks in sync with correct time.
EV motors are directly coupled via a fixed ratio reduction gear set in the final drive without a multi ratio transmission. This means that EV motor rotors are turning many thousands of RPM at highway speed and hence need excitation currents which could be in the tens of KHz range. A washing machine motor designer can almost disregard skin effect because at 50 or 60 Hz, skin depth is 7.6 mm, which is more than the typical conductor cross section. At 10 KHz is cold worked copper, skin depth is about 0.3 mm.
So there should be an annealling process between the forming and insulating processes, then?
Thank for explaining the phase shifting relative to the skin effect. Didn't know that was a thing but makes sense that it is.
The best explanation of skin effect I have ever heard. Thank you
You're so welcome!
It is one thing to know, another to teach. Fantastic explanation for someone like myself who is not an engineer. Crystal clear!
Great video and fantastic explanation of "skin effect"
Glad you liked it!
@@MunroLive Yep, one of the best explanations without diving into the math. I'd love to hear you delve into proximity effect ;-)
I don't think proximity is as important in motor. I've never done motor design, just high frequency magnetics where proximity effect is huge.
Master class in science communication, Paul absolutely knocked it out of the park here. One of my favorite Munro Live videos I've seen. This looked like it was one take as well? Super impressive!
Excellent video! Only someone who understands their subject very well can explain the engineering with the right amount of simplification. Many thanks. Can you do one comparing permanent magnet vs. induction motors in a similar style please?
Thank you, yes, I'm planning to do my next video comparing permanent magnet motors with induction motors. We see several examples of the two motor technologies appearing in the same car and understanding why can help us learn about how the vehicles are controlled.
@@PaulTurnbull-EMfield
Please include reluctance motors vs simple PM since Tesla is using that.
Love the low tech flip chart. Very comfortable as a viewer.
I didn’t.
I’ve no need to see talking head, written chart is worse still, just project the data like PowerPoint.
Munro Assoc is old school, not as bad as "After Hours", but old.
Who is the audience? I appreciate it (enormously), but no money from me.
PS. Content makes this one of the better vids I’ve seen, despite my niggle.
Awesome video! Paul is clearly both very knowledgeable and very passionate, but he's also a natural educator.
Great explanation. Wish you were my lecturer back in the day!
Very good video! I've worked on RFID coils, and at 100kHz and above you really start to see this effect. We investigated Litz wire, which is multiple stranded wire, but it didn't give us enough advantage to bother with the extra cost. Another issue is that if your cavity has too big of a cross-section, the inside of the cross-section is still affected by the magnetic field the same. This is probably why you see quite thin slots.
Well the effect depends on conductor size. In a 70mm2 cable 2kHz will double the resistance...
But in your thin antenna coil wire, 100khz might be correct.
Switching power supplies in the >100KW range use Litz wire in the active circuit. It looks like welding cable but the strands are insulated. You can get some that strips at soldering temperatures, but the good stuff you need to strip in hot acid.
The talk about frequency where the effect becomes an issue is not quite so simple. Depending what you are doing, you mau have near, or not so near sinusoidal AC current. Among other wave forms, you would consider trapezoidal current and square wave. Of these, the square wave represents a broad range of harmonic frequencies. The faster the slope of rise (and fall) of the change, the higher frequencies appear. With modern semiconductors (Fiel Effect Transistors) you can have 50 kHz base frequency producing one MHz or more harmonic frequencies. That puts the project into a different class from the automotive motor windings of this presentation. I just have personal experience of having to abandon solid copper wire due to scorching heat at 50 kHz coil choke. Litz wire with over 200 insulated strands solved the issue. By the way, we prepare the ends by dipping into molten tin in a Solder Pot.
@@InssiAjatonThanks for that, I completely missed the fact that the shape of the waves plays an important role, but it's obvious now. We did not need it because our RFID circuits used an LC tuned circuit with relatively little current flow, so we got a near perfect sine wave. Of course if you think about motors they often use trapezoidal waves, so much more harmonics as you say.
Regarding the AC resistance, the wire wound is not to be looked at as single wires but as a large conductor that is the aggregate of many of the single conductors. As such the skin affect is there like the hairpin wound as a net affect of the many winding's. The magnetic domain is not bound by the enamel covering. Thus the high speed advantage is greatly reduced I think. Great video and content. Some of the best I have seen here.
I was thinking exactly the same while watching the video
You’re not taking into account the boundary conditions where the conductors meet the insulator.
@@thinkmonkeymanlooks like it gets awfully complicated awfully quickly!
Happy to finally see the comparison. Like most everything in life, there are tradeoffs. Great video.
This was especially well presented, relevant, and interesting. More content from Paul would be awesome. Thank you for all your team's work.
Yelp, great teachers make the complex seem simple .
Amazing explanation! I didn't even know I didn't know!
“It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.“
That was a very well presented subject and helped a lot with the understading of such an interesting matter !
This channel is underrated, you guys rock! Thanks for making these videos. I support MunroLive :)
Much appreciated!
after a short warm up period, the talking got pretty good!
Great video. Thank you for explaining the difference between the 2 concepts so even I can understand with my basic knowledge.
Excellent presentation! Thank you for taking the time to put this together.
Thanks for the explanation, Paul -- I learned something today!
Cheers
Nice primer. This part really is the heart of the subject.
Now I will speak only in French to Sandy!!! Well done 👍
"Le Audi électrique car est étron"
@@f4c3l355 étron means dog poop in French... By the way, Sandy has a good accent in French.
@@gsbeakHe should, being born a Canuck.
@f4c3l355 hahah!
@@f4c3l355 That name is even more clueless than the Chevy No Va.
I am always so thankful I found this channel. Such GREAT content!!!
I appreciated this explanation and seeing the difference of the windings.
Thank you!
Great video and wonderful educational content. I’d like to see more of these videos Sandy!
Amazing detail! Yes, I wanted you to tell me that one is better for the city and one is better for the highway earlier, but I wouldn’t understood it if I didn’t have the full explanation.
Thank you
Félicitations pour votre français, cher ami ! Merci pour la qualité de vos vidéos. Salutations de 🇨🇵
Excellent video. Thanks for precise explanation of the difference between wire wound and hair pin stator design
I mean, with these videos why do I even need to go to University. Sooooo well explained and most importantly, VERY INTERESTING. Watched the whole video without realizing it was over.
Actually what he gives you is an explanation that would be adequate for a technician. The explanation is not sufficient for designing an efficient motor. And for most people that does mean going to college to get the proper training in math, physics and engineering.
@@googacctThen after you get your degree, you get a job and the shop tells you, you don't need anything you learned in college. This is the way we build motors so just design them using our normal standard method. We don't need you t9 design anything revolutionary or cutting edge.
What a great video and a superb teacher, thank you!
16:09 a bundle of insulated strands doesn't make the skin effect disappear, it is just the same as a solid wire the same size. Insulated strands is only an advantage if they a woven in way so that they all both equal amount inside and outside of the bundle over the length and share the current better
Good job new Paul!
Great educational video. Make more of them please.
Congratulations on a fantastic presentation. So well explained in one take! Wow
Excellent teacher.
Very informative and practical accessible information. I think I learn more about batteries and electric motors here than I did in HS classes in a lot less time.
It's easier to concentrate here, since they have such nicer toys.
Excellent presentation Paul. Thanks!
Thanks. Skin effect. Reminds me of when our Electrical Tutor told us as young apprentices that we would laugh when he told us how the early Car Radios produced AC from DC. and proceeded to explain to us youngsters about, "The Vibrator", about 55 years ago.
You are a great speaker, thanks for the quality information and insight you gave us!
THANKS PAUL 🤗 AND THE MUNRO TEAM , for explaining this in layperson’s terms 🤔💚💚💚
Paul is setting a new _bar_ @ munro ...
A very motor-vating presentation.
;)
Intresting how nomenclature can vary a bit in different parts of the same field. I work at a shop that repairs electric motors for industrial applications. We generally call them mush wound and formed coils instead of stranded/bar wound.
I also found it interesting to see some of the design considerations that go into the manufacturer side vs the repair side. From a repair standpoint stranded is much quicker for us to rewind. A half dozen different adjustable mandrel heads is sufficient for our winders to spin off a full set of coils ready to be stuffed into the slots in an hour. Those few heads work for most motors. Bar wound you need more spcalized jigs that are much more specific to that coil design. Worth it if your only working on a few types of motors or are specialized in making coils but not worth it for one off, bespoke repairs. We normally have to order in new preformed coils from a company that specializes in making them. That greatly impacts repair turn around. Stranded we can start putting in new windings as soon as the stator is striped and cleaned out, bar wound and your looking at at least a week to get the coils ordered, formed, and shiped to us and that's on an expedited schedule. Stranded windings we've had some where we could have the motor back to the customer in a day for an emergency repair.
These are really good videos, the deep dives are just super valuable!
No one on earth better than Munro!
Real education! Thanks
What a knowledable guy, and what an interesting topic. Fantastic video guys!
Thank you for the depth
*In a world where many things are “dumbed down” thank you for a decent explanation*
Most interesting; I shall have to come back to this when I’m ready for the design stage.
Thank you, excellent video! Paul's presentation is very clear, I'm looking forward to more videos with him hosting.
Thank you very much for another greatly insightful presentation of the current tech in motors used in BEV's
Thank you for explaining this!
Excellent presentation
Glad you liked it
Motors are confusing, and it's hard to find good info on the _whys_ of the differences in design. This video was an unusually good explanation of the physics and the corresponding effect on design choices. A fine example of someone who really understands their field.
Much appreciated. I too look forward to clarification of when induction is chosen and PM vs electromagnets.
Later on you might get to aluminium/iron motors maybe?
This is a great simple explanation of these 2 different type of motor. Lucid uses 8 bar design together with other patent technology to achieve by far the industry leading efficiency.
I think I've got it! Very well done/explained, thanks!! Hi Sandy!
Superbly presented 👍
That was a most intriguing expose' on winding vs. hairpin. And you managed to avoid any mention of 'inductance' throughout.
What's the scrap rate difference? Reliability? Durability? Nice explanation by the way. Another way of explaining is that AC current prefers traveling along the outside edge of the wire while DC travels throughout the entire wire evenly so having more wires increases the ability to carry more AC current efficiently.
VW seems to have big production problems with their new APP550 motor. I wonder how many bars they put into one slot.
Edit: Seems to be a stack of eight, too.
@@abraxastulammo9940They are also using 8. ua-cam.com/video/OoOuEn378gc/v-deo.htmlsi=PHGK3tC8vzFtc_1y&t=955
In my experience bar wound motors are more challenging to launch, but once the process is fully debugged it tends to be more repeatable and reliable than the stranded wound process.
@@PaulTurnbull-EMfield What do you think about the Ghent University research project on "Semi-Stranded Windings"' Revised: 25 January 2023?
Which seems to combine the advantages of both designs? What's the chance do you think it has to make it out of the lab and into production?
@@nc3826 Thanks for highlighting this very promising research. The paper very nicely illustrates the point that I was trying to make with my sketches. It's also nice that the paper isn't behind a paywall and is freely available. Thanks.
VERY GOOD explanation! AWESOME!
Brilliant Video Sir explaining the skin effect. This is why AC transformers use very thin laminations in their construction and why high end loudspeaker cable uses very fine and many conductor strands. So in an ideal world, the windings of an electric motor would be made from "hairpins" constructed from hair thick copper copper strands with enough ductile strength and elasticity to form the hairpins. So extrapolating that idea into a manufacturable component would mean having fine threads with a thick copper wrap, which would allow the manufacture of a bar like construction, with less resistance than the current wire wound. That would maximise the benefits of both. Example: 1mm copper sheet, encasing 1000 strand copper core ( length to be determined by the need to form, say 20% longer). This would allow the outer casing to be press machined to the hairpin and the part trimmed after forming. This would give the best of both worlds. 🙂
Thank you.
Outstanding clarity. Thanks, Paul
This is so amazing. Absolutely increible! I cant thank you enough.
Excellent Explaination ! Thanks !
Not only CEMF is an issue with AC cutternt/resistance but inreasing Frequency as well.... Good presentation!
@ the end of the day nobody gives a hoot as long as the car starts and the lights come on...!
Best explanation of skin effect i ever heard! Thank you!
Something in this video really hit me. In contrast with modern infographics and animation video, that chartboard and physicals examples maybe your tone and gesture make me feel calm emgage and enjoy watching.
Great explanation! Very informative!
Wow, just wow. I never thought I would understand physics that easily. You just triggered multiple "Aha"-moments for me. Thank you
Excellent explanation! Much appreciated, thank you!
Loved this! Thanks, Paul!
Excellent! Thanks for the great explanation.
Awesome explanation of the difference between bar and wire wound motors - fascinating!....
Thanks for teaching us! I just thought all electric motors are extremely efficient and it's the PWM / voltage that was the main driver for differences/sizing. Didn't realize the windings contribute so much. It would be great to see the spec sheet comparisons for two similar motors to understand the real-world effect of the decision, versus and illustrative line. Thanks again, great stuff!!
Thank you. That was the clearest explanation of the skin effect I have heard yet; very easy to understand as you described it.
Thanks, this helps me understand back-EMF a lot better than I did before.
Superb explanation about ac vs dc resistance!
Good information, answered many of my questions about motors. Only feedback is get rid of the yums.
I guess the broader context here is optimizing for specific speed rangers. Many industrial applications want a very high and constant speed so stranded is optimal. Vehicle applications with variable low to moderate speeds (attached to a fixed ratio gearbox) are slow enough that different bar designs can pay off.
Weight and motor size is not so important in the industry.
It's not the rpms that are important, it's the current frequency. In cars it varies between 0 and 600Hz, but in industrial motors it is fixed at 50 or 60 hz.
Esp with Plaid motor passing 20,000 rpm, still having flat power curve.
There’s some magic.
To think Porsche started with 2-speed gearbox, Jeep still wanting multi speed transmission, same for many legacy semi-trailers.
Very distinctive hands-on explanation of AC/DC reaction resistance in mass-energy-momentum continuous field/dimensionality integration with the device design. Thanks.
Keep these vids coming !!!❤
This is a great video. Brought the concepts of these motors to a very understandable level.
Thank you for the video, I did not know about the inverse relationship between the thickness of the hairpin bars and the improve frequency of the motor.
Phenomenal explanation! Very well done.
Great explanation. Thanks!
The slot fill difference isn't just due to the number of strands and thus the space taken by insulation - rectangular cross-sections of bar windings nicely pack into a rectangular slot, compared to round cross-sections of "stranded" windings... plus the small round wires are not neatly organized into an ideal packing pattern.
Very well explained, thank you for your efforts.
Thanks. So well explained I understood.
Great video I have a better understanding!!
Great explanation, thanks Paul. Thanks Sandy, your channel is invaluable.
This is a great explanation of electric motors for cars. It's absolutely amazing that century old technology is almost as good as the present day. As mentioned in other comments, I am asking for a comparison between permanent magnet and induction motors.
Fantastic video with clear and well spoken explanation! And no filler words whatsoever! Excellent. Please have the younger presenters at Munro Live watch and learn from the older guys (who speak so much better)! Thanks.
Thanks for making these amazing educational videos
Wow. What I don't know could fill volumes.