Getting Wound Up: Stranded vs Bar Windings in Electric Motors

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Another EXCELLENT video aimed at the ‘semi-geek’ for EV technology. Thank you for making understanding THE priority.

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 👍

I think this was one take. Impressive. Thank you for your service!

Twenty minutes well spent! Great video

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?

The best explanation of skin effect I have ever heard. Thank you

Great video and fantastic explanation of "skin effect"

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!

It is one thing to know, another to teach. Fantastic explanation for someone like myself who is not an engineer. Crystal clear!

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?

Love the low tech flip chart. Very comfortable as a viewer.

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.

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.

Great explanation. Wish you were my lecturer back in the day!

This was especially well presented, relevant, and interesting. More content from Paul would be awesome. Thank you for all your team's work.

Happy to finally see the comparison. Like most everything in life, there are tradeoffs. Great video.

Now I will speak only in French to Sandy!!! Well done 👍

Amazing explanation! I didn't even know I didn't know!

after a short warm up period, the talking got pretty good!