Axial flux motors with PCB stator - Page 1
Forum section: electronics / general

author: tszaboo
author_rank: Super Contributor
timestamp: December 18, 2022, 08:31:40 pm
content: What are they? They are a clearly working technology that has been demonstrated by people like Carl Bugeja.There seems to be a large number of companies claiming that these have a bunch of benefits and this is the technology of the future replacing motors everywhere. Yet I cannot really find any end products that would use this, or they are using it and not advertising it as such. I find motor design a fascinating subject that I clearly don't know enough about. Do these really work?The claims that they are making:- Ultra-lightweight- Superior Efficiency - Up to 96%- Acoustically quiet- Reduced materials - Up to 80% less copper- Low electromagnetic interference- Smooth motion - No coggingSo where is the catch? If it's superior, why aren't there any products using it? If it's not working well, why? Is this just a too new tech that is yet to make it's breakthrough?

author: Gyro
author_rank: Super Contributor
timestamp: December 18, 2022, 09:00:14 pm
content: Yes, they've been around for donkey's years. Printed Motors were possibly the first...https://www.printedmotors.com/e03produkte/e01dc_serie/e01kn_motor/index_eng.htmlThey are very good servo motors, I have an old one and, as you say, very efficient, low mass rotor and zero cogging, it runs down to nearly zero volts (less than 5rpm). The only disadvantage that I can see is wear. Mine has 4 carbon brushes running on the FR4 PCB disc. The 'commutator' section was originally Gold plated but half of it has worn off and the brushes are now working their way through the copper! Mine is very heavy, but it's pre-Neodynium magnet, probably AlNiCo.P.S. If you can find a used one, they're ideal for coil winding jigs.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: December 18, 2022, 10:31:16 pm
content: They are lighter and so used extensively in electric vehicles. It’s still a motor so won’t replace a cheap mass-produced one.I made a diy one as a turntable direct drive motor. Unlike the one shown in your photo I used three offset windings driven by three phase sine wave. Worked great.Brinkman makes a similar one.Regards,Randall

author: notsob
author_rank: Frequent Contributor
timestamp: December 18, 2022, 11:29:35 pm
content: I've seen them (with a printed circuit rotor) in tape drives before the use of cassette farms they were not long lasting (a few years at best), were used to drive the capstains - very quick start and stop profile for moving the magnetic tape.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 19, 2022, 09:37:40 am
content: I have seen sich a motor in a floppy disk drive.A problem with using a PCB as winding is that there is normally still a lot of isolation material and little copper. So the winding fill factor is low, unless one uses multilayers with > 20 Oz copper.So expect more like an inferiour efficiency . Maybe up to 96% if with a similar rotor design and conventional coil one may reach 98%.They may still be useful, for low power use that needs many poles and smooth operation. So like a tape drive, disc drive, turn table, maybe a fan or similar.

author: mzzj
author_rank: Super Contributor
timestamp: December 19, 2022, 03:19:29 pm
content: edit: replied accidentally to wrong thread.

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2022, 07:22:08 pm
content: I thought it would be good to get my Printed Motors PCB rotor motor out and take a few photos. In this case, it is a 24V 3300rpm motor with 42 oz.in continuous and 375 oz.in instantaneous torque - these things are designed as servo motors with rapid start, stop and reversals. These motors are still very much current technology, with many variants available, the justification seems to be that they can react faster than a brushless one and can run at really low speeds without cogging. The motor overcomes brush friction and starts turning at 0.3V with no cogging. I cleaned the rotor for one of the photos, but you can see that the brushes run on the slanted (curved) area of the PCB 'windings' with the 4 brushes at interesting angles - I'm not sure of the magnetic field pattern.P.S. Photos shuffled by forum.

author: tszaboo
author_rank: Super Contributor
timestamp: December 19, 2022, 10:40:00 pm
content: Quote from: Kleinstein on December 19, 2022, 09:37:40 amhttps://pcbstator.com/news/ecm’s-pcb-stator-whats-your-motorHere is one which is claimed to be 2.2kWh. With 600g copper. That looks to me like a 200mmx200mm pcb, so that would be roughly 60g of copper per layer with 100% filling, and 4 oz copper. Either it's ~16 or more layers or they use more than 4 oz. Or my math is off.Quote from: Gyro on December 18, 2022, 09:00:14 pmBrushes? So there the PCB is on the rotor, or is it not with permanent magnets? With the PCB as stator design, there are no brushes, and the rotor has permanent magnets. The construction is so simple, this guy makes them with 3D printers and cheap PCBs ordered from you know where:

author: uer166
author_rank: Super Contributor
timestamp: December 19, 2022, 10:50:49 pm
content: I believe the main issue here is copper density and mechanical support/design. The former is simply due to fiberglass construction of PCBs, the latter is a general issue with axial flux motors, regardless of how they're made, which is why they've been used for the ultra high-end, but not normal-ish cars. Something like a Model 3 drive unit is quite optimized for cost/power/size, and it's a regular old wound motor (not even hairpin). I doubt you'll find PCB-wound motors in the ~200kW+ range that EVs use, there's simply no point since those PCBs wouldn't look anything like a regular circuit PCB anyway, at which point it'll become its' own process/design..

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2022, 10:52:26 pm
content: Quote from: tszaboo on December 19, 2022, 10:40:00 pmYep, I totally misread your thread title as PCB rotor rather than stator somehow, I only noticed today. Having made the mistake, it still seemed unusual enough to be worth throwing in a few photos in case they were of interest!

author: uer166
author_rank: Super Contributor
timestamp: December 19, 2022, 10:52:57 pm
content: Quote from: RandallMcRee on December 18, 2022, 10:31:16 pmAs a drive/traction unit? I've never seen anything resembling PCB stators in EV traction systems. So far it's either classic wound stators, hairpin, and the very rare/occasional axial flux (but no PCBs).

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: December 20, 2022, 03:25:19 am
content: Quote from: uer166 on December 19, 2022, 10:52:57 pmWell, Mercedes and Ferrari are proponents—of axial flux, not necessarily the pcb stator bit.I read this articlehttps://spectrum.ieee.org/axial-fluxwhen it first came out…guess I’m a fanboy.

author: floobydust
author_rank: Super Contributor
timestamp: December 20, 2022, 05:15:04 am
content: I think the PCB stator is largely a dream for larger motors, electric cars etc. it cannot scale up.Why? For higher voltages you can't achieve the high number of turns, copper is limited to a thin strip with insufficient current handling (via's included) and isolation voltage, and lastly you can't get rid of the trace's heat with FR-4 as an excellent thermal insulator.I think 5HP is the most I've heard of- with no pictures from the manufacturer.Let's lure in naive investors and tout the labour savings of the PCB stator- even though the bulk of the motor's cost is in the rare earth magnets.

author: Gyro
author_rank: Super Contributor
timestamp: December 20, 2022, 08:59:41 pm
content: Ah, that IEEE Spectrum article answers a lot of the questions I had about the PCB stator approach. In comparing against my (OT) printed rotor motor - which has a very thick steel 'pole disc' creating a very small high flux magnetic gap for the rotor to run in. Trying the same backplate approach on a PCB stator would have resulted in huge eddy current losses, I'd come to the conclusion that having the backplate 'pole disc' spinning with the magnet assembly, closely sandwiching the stator PCB, was the only way it could be done. This sounded mechanically 'difficult' but it looks as if they have overcome any mechanical implementation difficulties. Stator heating through I2R losses is presumably tackled by keeping the R, and inductance,reallylow, together with radiation and the high speed airflow in the gap. The description says they have magnets on both rotating discs but the diagram shows one magnet disc and one plain.The one thing I still wonder about is how do they achieve damping the dynamic mechanical rippling of the PCB during winding switching, particularly in high torque situations. For efficiency, the magnetic gap needs to be really narrow and a bit of localalised board ripple could be a big issue.

author: Peter_Lee
author_rank: Newbie
timestamp: January 10, 2024, 11:22:03 am
content: I believe that the two magnets are positioned as marked in the diagram. Additionally, I have a question: how can one determine if a coil can still generate a sufficient magnetic field even after losing its core?