Determining cos phi from amplitude ratio of apparent power

摘要

The method involves electrically determining the output current and voltage, using analog-to-digital conversion, and a given equation to calculate cos phi from the amplitudes, before using a look-up table to carry out a stepped determination of the power factor The method involves electrically determining the output values current and voltage for determining cos phi and analog-to-digital converted in quantizing steps to determine cos phi according to an equation. cos phi = (SpoHW + SnegHW)/(SposHW - SnegHW) A stepped determination of cos phi is carried out according to a look-up table. In a first step, the amplitudes SpoHW and SnegHW are added. In a second step , the angle is computed from the quadratic function cos phi .cos phi . In a third step, the angle obtained in step is doubled. The cosine of the angle is determined to compute the power factor. The apparent power has a positive and a negative amplitude in a 50 Hz system in a time interval of 10 ms. The oscillation execution in the mains is facilitated by the wattless budget.