This behavior is also used in case of electrical faults in the electrical appliance, which the UPS is part of, in case of short circuits or arc faults. Also in these cases, the power demand at the UPS output excesses the capability of the inverter, and the control unit of the UPS causes a switchover to the bypass. In turn, the short circuit or the fault arc is directly fed by the power grid thus causing excessive currents in the current path leading to the short circuit or the fault arc. As a consequence, a circuit breaker in said current path cuts off power from the electrical fault and clears the situation. The UPS then switches over to conversion mode again and supplies the remaining parts of the electrical appliance with electricity. In case of a fault arc, the fault arc may be quenched by a short-circuiting switch, which quenches the fault arc by generating a short circuit between the conductors between the fault arc burns.

One should note that “excessive output current” and/or “excessive voltage drop” and/or “excessive power demand” at the UPS output in the above context particularly means an output current above a current threshold, a voltage drop below a voltage threshold or a power demand above a power threshold.

Existing methods are not focused on a reduction of the actual arc current, but are focused on cutting off the faulty areas of an electrical appliance from AC mains as fast as possible.

In contrast, this invention is using existing technology, that is a fault arc detection device, to control a UPS in a way to reduce the actual arc current by preventing the UPS from switching into bypass mode. As a consequence, the UPS feeds a fault arc with the inverter, wherein the current is limited by the inverter current limit, which is typically 2 to 3 times the nominal current and substantially lower than the arc current available from AC mains.