Apparatus for determining active and/or reactive current and/or the power thereof in an inverter with a given input d-c voltage, especially in a pulsed inverter

摘要

In an inverter, the phase, frequency and amplitude of the output voltage are determined by the switching signals for the inverter switches. By means of the switches which can be actuated by the same switching signals, the measured values corresponding to the phase currents are pulse width-modulated. The instantaneous values of the phase power formed thereby are optionally added to form the total active power sum. A characteristic stage can weight the sum signal with the reciprocal value of the voltage drive of the inverter, so that a signal is produced which is proportional to the active current. In a similar manner, also the reactive current can be determined by means of switches if the phase of the measured phase currents is shifted by &pgr;/2.