According to the three-phase current and voltage, the reactive power and power factor are calculated
The use of general instrument, including clamp meter, measuring a reactive power and power factor. There is no basis for calculation.
Clamp meter is the current transformer measurement is a valid value.
The measurement of reactive power requires the difference between the phase of the voltage and the phase of the current. If you measure only the current, or the voltage, it is impossible to come out. While measuring the current, the voltage is measured, the phase of both is sampled, and the phase difference is analyzed by the circuit, then the reactive power or the power factor are calculated. Clamp ammeters a function of such I had not seen.
