The article incorrectly implies that the only way to make a synchronous machine is with a permanent magnet, and thus all synchronous machines have temperature issues. On the contrary, it is entirely possible to build synchronous machines with driven rotors (e.g., through slip rings) that have none of the temperature issues associated with using permanent magnets (it's the magnets themselves that are temperatures sensitive, not some intrinsic property of the synchronous machine design). They are more expensive to manufacture than the good old squirrel cage induction motor, but synchronous machines in general are more efficient over a wider range of output rotational rates than induction machines, have somewhat better failure modes, and are much easier to start up.
In many cases, it's cheaper to (try to) solve these problems with smart drive electronics, i.e., add additional complication to the cheap part of the system rather than to the expensive part. But for the highest output machines---multi-megawatt generators, for example---synchronous machines remain king.
There are some other fun things you can do with motor drive electronics. A lab mate of mine in grad school wrote a cool thesis on using the iron in an induction machine as an electric transformer in such a way that the motor drive and power converter could be controlled independently. In essence, in a Y-connected three-phase system, the motor is insensitive to 3rd harmonic content in the drive signal, so you can pass energy through the air gap in the 3rd harmonic and rectify it on the other side to turn your induction machine into the magnetics for a power converter.
That's a pretty cool inductive motor hack. Personally, my favorite esoteric motor has to be the wobble motor built using electropermanent magnets (essentially, programmable permanent magnets):
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.
In many cases, it's cheaper to (try to) solve these problems with smart drive electronics, i.e., add additional complication to the cheap part of the system rather than to the expensive part. But for the highest output machines---multi-megawatt generators, for example---synchronous machines remain king.
There are some other fun things you can do with motor drive electronics. A lab mate of mine in grad school wrote a cool thesis on using the iron in an induction machine as an electric transformer in such a way that the motor drive and power converter could be controlled independently. In essence, in a Y-connected three-phase system, the motor is insensitive to 3rd harmonic content in the drive signal, so you can pass energy through the air gap in the 3rd harmonic and rectify it on the other side to turn your induction machine into the magnetics for a power converter.
http://dspace.mit.edu/handle/1721.1/28691