6 ms·

It's actually not an induction motor. It's likely synchronous, with the wound rotor actively energized.

baybal2 5y ago
Oh, bingo https://player.admiralcloud.com/?v=34a065e8-47e7-4a52-b679-fc46edea94f5 https://player.admiralcloud.com/?v=34a065e8-47e7-4a52-b679-f... That's a rotary transformer excited synchronous motor. A bit better, they are now only 90-80 years too late.
- Gibbon1 5y ago
  This pdf of a thesis covers the design. https://core.ac.uk/download/pdf/20328622.pdf https://core.ac.uk/download/pdf/20328622.pdf Here and elsewhere found two issues. A problem is efficiently driving the rotary transformer due to losses in the drive circuit because air gapped transformers have a lot of leakage inductance. I take that to mean they throw a lot of reactive power back at the drive electronics. Hidden problem they are trying to solve is these motors are typically/often oil cooled. Oil and slip rings don't play well together.
  - adrian_b 5y ago
    Thanks for the link, it is interesting. However the conclusion about the low efficiency of the electronic converter for the rotary transformer is no longer valid. With modern switches of silicon carbide or gallium nitride and with resonant soft switching techniques, the converter should operate at much higher frequencies and at much lower losses. This is what has probably enabled today the manufacturing of a high-efficiency synchronous motor with a rotary transformer by Mahle.
    - Gibbon1 5y ago
      We agree that issues with the inverter efficiency were fixable with modern designs and components. I'm on this train of thought that the service life of electric power trains is 2 to 5 times that of gasoline ones. There is a potential to design cars that last 30-50 years. Which potentially reduces the environmental impact of vehicles. I've noticed though that people in the automotive industry look at you like an moron when you suggest that the service life of cars may double or triple. I think it's so ingrained they can't think around it.
- imtringued 5y ago
  Even if the idea is old you still have to build it in a commercially viable fashion i.e. it has to be competitive with brushless motors. Not to mention the fact that EVs sparked an interest in rediscovering existing motor technology.
  - baybal2 5y ago
    It's not an idea. Externally excited synchronous motors are well widespread.
- loufe 5y ago
  I don't understand this attitude. If a company released an ICE engine with a different configuration than the standard that had been hypothesized and prototyped 100 years ago would you be singing the same tune?
  - baybal2 5y ago
    > hypothesized and prototyped 100 years ago It's not hypothesized and prototyped 100 years ago, it's the most common type of medium power electric motor in the world.
- devmor 5y ago
  This isn't a physics discovery. It's an engineering application. Engineers rarely invent new things, they improve upon existing things. Find me a brush-less, magnet-less electric motor like this with a 95% transfer efficiency.
  - baybal2 5y ago
    Simple induction motors easily get to 95% https://ouc.bizenergyadvisor.com/article/ac-induction-motors https://ouc.bizenergyadvisor.com/article/ac-induction-motors
  - jbay808 5y ago
    > Find me a brush-less, magnet-less electric motor like this with a 95% transfer efficiency. Turntide gets to about that level with their high-rotor-pole switched reluctance motors, I think: https://turntide.com/learning-center/ https://turntide.com/learning-center/

Oh, bingo https://player.admiralcloud.com/?v=34a065e8-47e7-4a52-b679-fc46edea94f5 https://player.admiralcloud.com/?v=34a065e8-47e7-4a52-b679-f... That's a rotary transformer excited synchronous motor. A bit better, they are now only 90-80 years too late.

Gibbon1 5y ago
This pdf of a thesis covers the design. https://core.ac.uk/download/pdf/20328622.pdf https://core.ac.uk/download/pdf/20328622.pdf Here and elsewhere found two issues. A problem is efficiently driving the rotary transformer due to losses in the drive circuit because air gapped transformers have a lot of leakage inductance. I take that to mean they throw a lot of reactive power back at the drive electronics. Hidden problem they are trying to solve is these motors are typically/often oil cooled. Oil and slip rings don't play well together.
- adrian_b 5y ago
  Thanks for the link, it is interesting. However the conclusion about the low efficiency of the electronic converter for the rotary transformer is no longer valid. With modern switches of silicon carbide or gallium nitride and with resonant soft switching techniques, the converter should operate at much higher frequencies and at much lower losses. This is what has probably enabled today the manufacturing of a high-efficiency synchronous motor with a rotary transformer by Mahle.
  - Gibbon1 5y ago
    We agree that issues with the inverter efficiency were fixable with modern designs and components. I'm on this train of thought that the service life of electric power trains is 2 to 5 times that of gasoline ones. There is a potential to design cars that last 30-50 years. Which potentially reduces the environmental impact of vehicles. I've noticed though that people in the automotive industry look at you like an moron when you suggest that the service life of cars may double or triple. I think it's so ingrained they can't think around it.
imtringued 5y ago
Even if the idea is old you still have to build it in a commercially viable fashion i.e. it has to be competitive with brushless motors. Not to mention the fact that EVs sparked an interest in rediscovering existing motor technology.
- baybal2 5y ago
  It's not an idea. Externally excited synchronous motors are well widespread.
loufe 5y ago
I don't understand this attitude. If a company released an ICE engine with a different configuration than the standard that had been hypothesized and prototyped 100 years ago would you be singing the same tune?
- baybal2 5y ago
  > hypothesized and prototyped 100 years ago It's not hypothesized and prototyped 100 years ago, it's the most common type of medium power electric motor in the world.
devmor 5y ago
This isn't a physics discovery. It's an engineering application. Engineers rarely invent new things, they improve upon existing things. Find me a brush-less, magnet-less electric motor like this with a 95% transfer efficiency.
- baybal2 5y ago
  Simple induction motors easily get to 95% https://ouc.bizenergyadvisor.com/article/ac-induction-motors https://ouc.bizenergyadvisor.com/article/ac-induction-motors
- jbay808 5y ago
  > Find me a brush-less, magnet-less electric motor like this with a 95% transfer efficiency. Turntide gets to about that level with their high-rotor-pole switched reluctance motors, I think: https://turntide.com/learning-center/ https://turntide.com/learning-center/