It should be noted at this point that the embodiments and associated advantages disclosed in the context of the online, double-conversion UPS, the combined power supply and arc quenching device and the electrical appliance equally apply to the method of quenching a fault arc in an electrical appliance and vice versa.

Generally, same parts or similar parts are denoted with the same/similar names and reference signs. The features disclosed in the description apply to parts with the same/similar names respectively reference signs. Indicating the orientation and relative position (up, down, sideward, etc) is related to the associated figure, and an indication of the orientation and/or relative position has to be amended in different figures accordingly as the case may be.

FIG. 1 shows a prior art online, double-conversion uninterruptible power supply 1a, which comprises a UPS input 2, a rectifier 3, which with its input is connected to the UPS input 2, an inverter 4, which with its input is connected to an output of the rectifier 3, a UPS output 5 being connected to the output of the inverter 4, a bypass switch 6 between the UPS input 2 and the UPS output 5 and a control unit 7 for closing the bypass switch 6 in case of excessive output current and/or excessive voltage drop and/or excessive power demand at the UPS output 5.