Device for detecting active and/or reactive current and/or their power in an inverter with predetermined input DC, particularly a pulse-controlled inverter

摘要

In an inverter, the switching signals for the inverter switches determine the phase angle, frequency and amplitude of the output voltage. Measurement values (iU, iV, iW) corresponding to the phase currents are pulse-width-modulated by means of switches (MU, MV, MW) which can be operated by the same switching signals. The resultant instantaneous values of the phase power are added (7), if necessary, to the total active power. The sum signal can be weighted with the reciprocal value of the voltage modulation of the inverter by a curve-generating element (8), so that a signal (IW) proportional to the active current is produced. In the same manner, the reactive current can also be determined by means of switches (BU, BV and BW) if only the phase of the phase current measurement values is shifted by pi /2. IMAGE