How much power can a generator make?

The famous Big Allis ( an Allis-Chalmers generator made originally in l959) and possibly still in use though re-armatured a number of times, was rated-after preliminary tests at the Argonne National Labs-they intended to use it for atojm-smashing , not regular power generation, at get this, l5 BEV. BEV? Billion Electron Volts, don"t spend it all in one place, it was claimed the exciters or starting motors alone drew l5 MEV (Million electron-volts) Popular Mechanics sang the praises of this famous generator that could (Jack the energies up to l5 BEV!) There you have it. There are probably higher powered units for purely experimental work bit iI"ll stand by Big Allis.