Such things exist: https://en.wikipedia.org/wiki/Superconducting_electric_machine https://en.wikipedia.org/wiki/Superconducting_electric_machi... A purely (dou

Such things exist: https://en.wikipedia.org/wiki/Superconducting_electric_machine https://en.wikipedia.org/wiki/Superconducting_electric_machi... A purely (doubly fed) superconductive motor would probably resemble a PM motor more than an inductive motor, but I'm not 100% sure. It would be for the same reduction in hysteresis losses. An air-core motor would also be possible, but that would result in 30 Tesla fields swinging around wildly, which would be a Bad thing. You could probably get good gains with metal glass laminations, if you were gonna make a hilariously expensive motor. It's got very low core loss and extremely high permeability, which lets you shrink the motor and have a higher ratio of copper/iron, lowering winding resistance. Still, electrical machines are so efficient it's kind of just not worth it. The friction in the bearings and the viscosity of air are significant factors in a motor's efficiency.