New kid in town. They develop axial flux PM motors for EV (like YASA).
https://www.magnax.com/electric-transport
https://www.magnax.com/electric-transport
Yeah, but the 0,12 kW/kg is for a 16 kNm torque generator machine running at 60 rpm which is a pretty low RPM.Sure, check it out, but don't expect too much: aside from the issue that Magnax has probably never built an e-bike sized motor, keep in mind that nothing scales that easily, so the power density and efficiency in a small motor will not be the same as in a large motor... and the one example they have is very large.
Also, while they claim 15 kW/kg, the one motor spec they publish is for an 850 kg and 100 kW motor - that's only 0.12 kW/kg!
I agree that the power density problem in this case is low speed, but the only real motor they have (allegedly) built doesn't demonstrate what they claim. I say "allegedly" because the torque and power output graph published in the spec sheet is an obvious fake (perfectly straight-line constant torque), rather than an actual test result.Yeah, but the 0,12 kW/kg is for a 16 kNm torque generator machine running at 60 rpm which is a pretty low RPM.
Smaller motors run in the x thousands RPM and according the formula kW goes up linearly with RPM...
That makes sense.My experience with axial flux linear motors is that generally these machines scale up well, but not so much scaling down. These sort of large diameter machines would work great for drilling oil wells.
Hmmm??.... Sounds like a small drive unit for a pumped Hydro dam turbine !......
Can you imagine that 1.6 m diameter motor running at 6,000 rpm, putting out 16 kNm and 10 MW? ........
Hi,That makes sense.
An example they mention in the whitepaper is a wind turbine, which is even slower and larger. Direct-drive wind turbines have been tried (probably for decades), but have not yet shown a clear advantage over higher-speed machines with gear drives. 100 kW is very small by commercial wind turbine standards and used only in remote locations; to produce the 2 MW at 15 rpm of a mainstream turbine, a stack of 80 of the featured Magnax units (weighing an unworkable 68 tonnes) would required! Obviously they could scale up - they would need to. It's not apparent to me how a Magnax machine would have any advantage over the Siemens and General Electric direct-drive machines (which appear to be radial-flux) that have been doing this job for several years.
Hi Brian,Sure, check it out, but don't expect too much: aside from the issue that Magnax has probably never built an e-bike sized motor, keep in mind that nothing scales that easily, so the power density and efficiency in a small motor will not be the same as in a large motor... and the one example they have is very large.
Also, while they claim 15 kW/kg, the one motor spec they publish is for an 850 kg and 100 kW motor - that's only 0.12 kW/kg!
I don't see any reason to expect better than YASA's product, which run up to 6.7 kW/kg in the P400 series.
Daan, thanks for your response.Hi,
This is Daan from Magnax.
Interesting discussion here. Allow me to give some additional information.
For our axial flux topology, torque quadruples when the diameter doubles. So for a 2 [email protected] 15 RPM generator, we would recommend:
- A stack of 8 discs of 4m diameter (total generator weight: 16 tons). delivers 1243 kNm
or
- A stack 5 discs of 5m diameter (total generator weight: 12,5 tons). delivers 1254 kNm
The weight of traditional direct-drive = at least 40 tons.
For a 2 MW turbine, I don't expect nacelles with larger diameters than that. But if so, the weight benefit increases even more.
Each disc has an axial length of 14cm.
Best regards,
Daan
That does make sense; however, originally it didn't say that. I drafted my reply in email, from the emailed notification from the forum, and copied and pasted directly from his original text (shown below). I didn't notice that by the time I logged in and posted, Daan had edited his post. That part was my error.Brian,
Daan's comment was " torque quadruples when the diameter doubles". .
..implying a second power (proportional to the square of the diameter) relationship.
Daan, thanks for the correction.Hi,
This is Daan from Magnax.
Interesting discussion here. Allow me to give some additional information.
For our axial flux topology, torque quadruples with the diameter. So for a 2 [email protected] 15 RPM generator, we would recommend:
- 8 discs of 4m diameter (generator weight: 16 tons). delivers 1243 kNm
or - 5 discs of 5m diameter (generator weight: 12,5 tons). delivers 1254 kNm
Each disc has a length of 14cm.
The weight of traditional direct-drive = at least 40 tons.
Best regards,
Daan
By the time I added the geared example, I had also reversed the torque and force values when I pasted them in! I blame distractions while I was doing this.If the torque varies as the cube of the diameter, and the largest possible hub motor for a car is about 400 mm in diameter, it would produce only 1.6% of the torque, or 250 Nm. With a minimum tire radius of about a third of a metre, that's 83 N of thrust per wheel... enough for a bicycle, but not a car. Maybe the torque reduction only varies as the square of the diameter (because hey, let's be optimistic): then you get 6.25% of 16 kN or 1000 Nm, for 333 N of thrust... still not nearly enough. For comparison, a Nissan Leaf motor puts out 280 Nm, and that's multiplied by 7.9377:1 reduction gearing to produce 661 Nm at the wheels, or 2223 N of thrust... which is what is needed for a couple of tons of car to accelerate acceptably.
Good call.I removed the in-wheel picture from the website since it gives people the impression that we do in-wheel powertrains. But we only deliver the AF motor. How customers implement the motor (in-wheel or chassis) is their choice.
The power and torque correspond to the maximum speed for both nominal and peak conditions (260 Nm at 5500 RPM is 150 kW; 521 Nm at 5500 RPM is 300 kW), which is like the published chart for the 1.6 m diameter motor, but unlike normal high-speed motor characteristics: normally, the peak current (and so peak torque) cannot be sustained past some point as speed rises, so torque drops off in proportion to speed and the power output is roughly constant for the remainder of the speed range.The first motor we are going to release is the 265 mm version. This one will have the following specs:
- 5500 RPM
- 265 mm motor diameter
- 86 mm motor length
- Peak power: 300 kW
- Nominal power: 150 kW
- Peak Torque: 521 Nm
- Nominal Torque: 260
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The reason why our power densities are so high is because of a new patented cooling system (which seems to be very effective and results in significant higher current density in the windings) and the use of grain oriented electric steel. (much higher flux density in the magnetic cores).
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