My problem is I want to calculate three phase kilo watt hour from time sampled data of current and voltages.
My doubts
1) How can I calculate the kilowatt hour from time sampled data? Is it any equations is available?
2) Is it need to take the phase shift ? ( How can I calculate the phase shift from sampled data of voltage and current? How I link this to calculating the three phase power.)
3) Please suggest me if some better platform is available for solving my doubt?
4) Is it true when I calculate the kilowatt hour of each phase separately and some up all?
I get the instantaneous sample value (Not continues).(I have some sensors that gives the current and voltage – I convert this to digital for processing). Around 50 samples are got from 1sec.(Is it to be zero when we some up all the power of three phase – due to phase shift of 120) . How can I calculate total three phase kilo watt hour from these sampled value. I am processed my data in arduino.
Best Answer
It depends on your load. If you have a symmetrical load which sinks a sinusoidal current and power changes relatively slow, then what you're doing works. You can calculate the power at each sample by:
$$P = U_1 \cdot I_1 + U_2 \cdot I_2 + U_3 \cdot I_3$$
Sum all samples up and you will get the desired energy \$W\$. For example with 50 samples/s:
$$W = \frac{\Sigma P}{50} ~~[Ws]$$
But if your current is not such a nice sine and your power consumption changes fast (within 1 period) than you need much more samples than 50/s (as Andy aka said).