Hence, generally, an online, double-conversion uninterruptible power supply is of advantage if the signal causing the bypass switch held open

• • i) turns off the inverter (independent of whether there is a battery being connected to the output of the rectifier and to the input of the inverter or not), or
  • ii) turns off the rectifier if there is no battery being connected to the output of the rectifier and to the input of the inverter, or
  • iii) turns off the rectifier and disconnects the battery from the inverter if there is a battery being connected to the output of the rectifier and to the input of the inverter.

In yet another advantageous embodiment, the inverter is turned off and/or the rectifier is turned off and/or the battery is disconnected from the inverter when said signal is received and an output current at the UPS output is above a predetermined current threshold. Accordingly, superfluously cutting off the electrical appliance, which is fed by the online, double-conversion UPS, is avoided.

Furthermore, it is advantageous if the inverter is turned on again after a (first) predetermined time span and/or if the rectifier is turned on again after a (second) predetermined time span and/or if the battery is connected to the inverter again after a (third) predetermined time span. In this way, the online, double-conversion UPS changes over to normal operation automatically after the fault arc has been quenched. The first, second and third time span may differ from one another or may be the same.