Short circuit detection apparatus

A short circuit detection apparatus for detection of an electrical short circuit current flowing in at least one monitored current path from a voltage source to an electrical load, wherein the short circuit detection apparatus is connected to the monitored current path and comprises an evaluation circuit including:

• at least one programmable or preprogrammed arithmetic unit adapted to perform at least one arithmetic combination operation, ACOP, on a first voltage, UR, provided by a resistive element of the monitored current path and being proportional to the electrical current, I, flowing via the monitored current path and on a second voltage, UL, provided by an inductive element of the monitored current path and depending on a derivative of the electrical current, dI/dt, flowing via the monitored current path to provide a combined sensor voltage and including
• a comparator adapted to compare the combined sensor voltage provided by the programmable or preprogrammed arithmetic unit with a preset or an adjustable threshold voltage to generate a short circuit detection signal (SCDS) if the combined sensor voltage exceeds the threshold voltage,
• wherein the first voltage, UR, and/or the second voltage, UL, are amplified by an associated amplifier of the evaluation circuit to provide amplified voltages, wherein each amplifier of the evaluation circuit comprises an adjustable gain and an adjustable offset, wherein the amplified first voltage, UR_amp, output by a first amplifier of the evaluation circuit and the amplified second voltage, UL_amp, output by a second amplifier of the evaluation circuit are both supplied as input to the programmable or preprogrammed arithmetic unit of the evaluation circuit which is adapted to perform the at least one arithmetic combination operation, ACOP, on the input amplified voltages to provide the combined sensor voltage applied to the comparator of the evaluation circuit, wherein a first sign of the amplified first voltage, UR_amp, output by a first amplifier of the evaluation circuit and a sign of the amplified second voltage, UL_amp, output by a second amplifier of the evaluation circuit are both determined and evaluated, wherein if the first and second sign are not equal the generation of the short circuit detection signal is automatically inhibited to avoid a false triggering of the comparator of the evaluation circuit.