A tape roller bearing is provided that prevents the development of an air film between the roller surface and the tape. This drive unit is characterized in that the drive circuit performs drive control of the motor through the output of electric power from the chargedischarge portion or the output of electric power from the chargedischarge portion and the fuel cell. Said means to prevent the escape of air are placed between the means provided within the said film and the reel. Responsive to loss of the power source, the UPS may be used to maintain operation of the generator as an induction motor while the prime mover accelerates up to a speed sufficient to drive the generator as an induction generator.