5 ms·
The catch is that radial motors are balanced magnetically and these are not. All that magnetic force is added to axial pull between the stator and rotor. That
by ew6082 7y ago
The catch is that radial motors are balanced magnetically and these are not. All that magnetic force is added to axial pull between the stator and rotor. That means they need a thrust bearing in addition to the guide bearings. This causes increased heat and mechanical losses and probably limits efficiency to somewhat less than a standard electric motor. Hi-E standard motors cap out around 98.8%, these will probably cap a point or two lower.
- nomel 7y agoI don’t have a firm grasp of the article, but isn’t the force balanced in this case since the two rotors, linked together, sandwich the stator? If I understood correctly, this would mean the thrust bearing would only feel the imbalance between the two sides. See: https://m.youtube.com/watch?feature=youtu.be&v=BTuCshX5bc0&t=36 https://m.youtube.com/watch?feature=youtu.be&v=BTuCshX5bc0&t...
- japanuspus 7y agoAgreed, this seems to be an incorrect conclusion. Maybe ew6082 just looked at the asymmetrical figure without reading the text.
- ew6082 7y agoFair enough. They said that a double rotor version has been developed, but all their prototypes and marketing material are single rotor. We can probably assume that single rotor is all that would fit on an in-wheel design but there are other ways to skin the cat. They would still need to include a light thrust bearing on the double rotor design since you can never assume perfectly balanced air gap and one side or the other will dominate, but the losses would be much lower with that setup.
- mannykannot 7y agoIn general, yes, though the article mentions one in-hub motor with a single rotor, for reduced size or weight. I guess an in-hub motor, which also acts as the wheel's axle, has to deal with much larger axial forces, from cornering, than those generated by the motor, so the latter are moot. Also, during operation, is not each magnet in the motor being simultaneously pulled by the pole it is moving towards, and pushed by the pole it is moving away from? If so then, at any given point in the rotation, the axial force would be the net of the two effects.
- regularfry 7y agoThey're claiming higher efficiency because of less iron loss. Does it balance out?
- burpsnard 7y agohttps://www.researchgate.net/publication/262642389_Axial_and_Radial-Flux_Permanent_Magnet_Generators_for_Direct-Drive_Wind_Turbines https://www.researchgate.net/publication/262642389_Axial_and...
- Sammi 7y ago"ABSTRACT: The application of permanent magnet machines as direct-drive generators for wind turbines is considered. The Axial-Flux Permanent-Magnet (AFPM) machine with slots is compared to the Radial-Flux Permanent-Magnet (RFPM) machine, for this application. Using a computer-based design model, the two machine types are optimized with respect to the lowest Cost/Torque. Design optimization for maximum Torque/Volume is also investigated. The calculations show that the RFPM machine has lower Cost/Torque than the AFPM machine with slots, and lower torque/volume than the AFPM machine with slots. ... Conclusion... ...Based on the results presented herein, the RFPM machine still appears as a better choice for a direct-drive generator, than the AFPM machine with slots"
- JorgeGT 7y agoFor vehicles (cars, planes, etc.) if they can mass-produce at 97-98% efficiency and the power-to-weight ratio they are claiming to achieve (15 kW/kg) then it's still a huge improvement.
- pinkfoot 7y agoYou will find on enquiry, as I have, that under continuous load the power density is a LOT lower.