Voltage converter for measurement function in low voltage (LV) power switch

摘要

The voltage converter includes a first voltage divider formed of resistances, as well as a voltage isolation component consisting from an amplifier and a transformer. A second voltage divider (ST2) for at least one phase of the line supply (L) is arranged separately to the first voltage divider, and is connected to it through a switching contact (SK). The outputs (A1, A2) of the voltage dividers are connected over a switch (Sl) with the voltage isolation component. The switch is controlled by a comparator (K) which is likewise connected with the outputs of the voltage dividers, in such way, that the output with the higher voltage is connected at any time to the voltage isolation component.