The zero crossings of the voltage waveform has to be taken as zero crossing ref...The current waveform square wave zero crossing needs to be compared against and a pulse developed to switch ON and OFF ..Width of this pulse is proportional to the powerfactor ....A Volt to Freq converter gives a readout
sir, we can't directly give the current input to the comparator and a resistance will be used to convert the current waveform to voltage waveform but then this may change the value of power factor. and then we can't use zero cross detector for high voltages.
We cannot give current input to an OPAmp input stage..For this I had opted for use of a hall effect current sensor from Allegro //LEM which give the instantaneous waveforms of the current and can be used for the OPamp input stage.