What makes the generator practical?
In order for it to be practical the frequency of current must yield an inductive impedance about 10x to 100x the DCR of the wire. Otherwise it will not work. even at 50MHz it won't work unless highly tuned with heavy copper thin hollow core conduit. Then skin effects and RPM , inertial mass, imbalance etc make it impossible.

Thus the core in a generator must have a magnetization flux to couple the magnetic field thru the commutation DCR to generate any appreciable V*I= power.

otherwise the inductive impedance will just shunt or short out the magnetic field and generate very little voltage or current.  This can be done with permanent magnets, laminated iron core with an excitation field current to increase voltage etc.  

Do an impedance ratio calculation with a 0.1uH single turn and see what Z(f) you get at 60 Hz with conductor and current needed to 
get 1V then conduction losses and magnet strength in Tesla to get that current. You would need a cryogenic cooler and a superconductor.