Furthermore, the online, double-conversion UPS 1a comprises a battery 8 being connected to the output of the rectifier 3 and to the input of the inverter 4. The battery 8 may be an internal battery as shown in FIG. 1 or an external battery, which is connected to a battery connector between the output of the rectifier 3 and the input of the inverter 4. Alternatively or in addition, the online, double-conversion UPS 1a may comprise an internal or external capacitor connected to the output of the rectifier 3 and to the input of the inverter 4.

The online, double-conversion UPS 1a is part of a prior art electrical appliance 9a, wherein the UPS input 2 is connected to a power grid (AC mains) 10. Hence, the UPS input 2 forms a grid connection of the electrical appliance 9a to the power grid 10. The electrical appliance 9a comprises a number of appliance sections 11a, 11b, each having a number of electrical consumers, a number of short-circuiting switches 12a, 12b and a number of circuit breakers 13a . . . 13h.

The function of the electrical appliance 9a shown in FIG. 1 is as follows: