Determining magnitude of mains input voltage, involves determining mains transformer internal impedance from quotient of secondary voltage/current change resulting from applying load

摘要

The method involves measuring the secondary voltage (USek) of the mains transformer for conversion of the input voltage to a lower voltage and the secondary side transformer output current (ISek). An evaluation circuit determines the internal impedance of the mains transformer from the quotient of the secondary side voltage and current change resulting from connecting a load.