Brusa has an induction motor with magnets embedded in the rotor. At high torque, the induction overrides the permanent magnets. At lighter loads, the permanent field dominates and turns it into a synchronous motor.
"We propose a novel variation of a doubly-fed induction generator which aims to improve power density and simplify construction. Our design is a doubly-fed, dual-rotor, axial-flux, permanent-magnet machine."
The magnets for that thing were truly scary. Every once in a while I gave him a hand with the assembly and it took three or more of us to safely install each magnet in the rotor.
http://www.diyelectriccar.com/forums/showthread.php/evdl-syn...