Advantage

• No power cut

• As the supply power source of UPS is only batteries, the power supplying time is short (several minutes). To lengthen it, many batteries must be used.
• So, the maintenance work of many batteries is required.

Advantage

• Long power feeding period after power cut

Disadvantage

• There is a non-power period (because a certain length of time is required to start the engine generator).

• It is possible to restart the power supply within a half
  wavelength of the 50/60 Hz frequency after a power
  cut occured
  (which causes nomal function to computer).
• Long power feeding time during power cut period
  (capable to cope with a long blackout period)

• Detection of a blackout by computer
• With the use of an inverter for generator, the AC current to be supplied during a blackout period will be a sine wave with a distortion of less than 1%.
• The use of DC-DC converter enables to reduce the number of batteries.