Power Factor

How curious, the phase difference between the current and voltage is exactly what you need. Perhaps some one can explain a way to measure the phase difference from what you already know but I do not know how myself.

????
TT3

seems I need to buy 2 wattmeters, no wye neutral pullout

I was hoping there might be some trick to obtaining power factor or at least get a good estimate based on limited information

No calculation exists for only those two parameters that = PF.

Some standard assumptions exist, but are estimates about the average PF of certain situations (usually around 30⁰ lag).

If this is not a theoretical query and you want to make the calculation less frequently than would indicate buying 2 kW meters, then this link might be helpful.

Adding the phase angle to your information will allow you to calculate all of the values you inquired about.

guest: you do not mention the line to line voltage, is it? 380/220, or 480/277, why would want to measure neutral voltage to line voltage? watt meter rule is N minus lines, that is 3 phase 3 wire, 2 watt meters needed 3 phase 4 wire , 3 watt meters needed, this will give you the watts used. next you need a rms reading volt meter and rms, iron vane amp Reading meter, volts times amps give you volt/amps or KVA if measured against a Resistance heater they should be the same. if inductive load, reading the kva against the KW there would be a difference. perry

Where as "POWER FACTOR = REAL POWER ( KW) / APPARANT POWER ( KVA )" , this question came without a way to measure kW.

As for "= (KWH2 - KWH1 ) / TIME" , again he is able only to measure Line volts and Line amps. Besides, this equation makes no logical sense to me and I've metered and taught metering for a long time. You would have to explain the circumstances of these measurements, for instance is one measuring a purely resistive load of the same amps etc.

Also if "KWH2 / KWH1 ARE ENERGY METER READINGS", how do readings alone offer any useful detail? Are they readings of the same meter at different times? Are they a kWh meter and a kWh meter wired to measure kVARh?

Also "1.732 * V LINE * I LINE" is the formula for 3 phase VA. How can he use this without the phase angle, VAR or kW to calculate PF?

In brief, and not to be critical, can you clarify some of your references for the questioner please.

By kWh1 and kWh2 are the values read from the same meter at 2 different times. Making the difference of real energies (kWh) and dividing this difference by the time difference (t), it results the real (active) power (kW).

From the other readings (A and V) the apparent power can be determined, which, in turn, allows the calculation of the power factor as the ratio between real (kW) and apparent power (kVA).

This procedure allows the calculation of only an average power factor, in case the measured values of voltages and currents are also average values recorded along the same time interval. Otherwise mixing instantaneous measured values (A,V) with average values (kW) may lead to significant errors.

To determinate the power factor and thus reactive and apparent power with only current and voltage measurements is not possible.

thank you all for your inputs and thoughts,

expected little hope in calculation/estimating PF with such limited information and instrumentation on a 200 VAC line-to-line 400 Hz

I had always prefer to pull out the wye neutral and ground it for safety but as suggested I would need 3 wattmeters

400 hz? Where do you live? :=)