i need to roughly calculate kwh
i need to roughly calculate kwh
(OP)
I am trying to correct a bad power bill I know the amount of ampa i pulled and for the time period and i know the voltage of the incoming line and i know the pf how do i calculate the total kwh for a certain amount of time






RE: i need to roughly calculate kwh
RE: i need to roughly calculate kwh
RE: i need to roughly calculate kwh
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: i need to roughly calculate kwh
RE: i need to roughly calculate kwh
bad PF , if your PF is OK ( probably more from 0.92) you haven't pay additionals.
Of course you pay also according to TOU.
Biling report possible only with revenue meter.
But for some value, DPC recommendation OK, we check in this way utilities meter.
Regards.
Slava
RE: i need to roughly calculate kwh
This is scheme of a standard power counter used from all electro power companies in the world (electronically differ now but they work on basically same principle)
RE: i need to roughly calculate kwh
You are rather ill-informed for an electric engineer.
It is true that the device shown in your reference multiplies U and I. But it goes that microsecond for microsecond, not using an average or RMS value.
You could say that your method is scalar multiplication while the method used in kWh meters is vector multiplication. As we all know, you need to include the angle between the units to arrive at a correct answer when vectors are multiplied.
The angle, in this case, is the phase angle, phi, between U and I. And it enters the multiplication as cos(phi).
As you also should know, PF = cos(phi). We are limiting this discussion to sine waves and linear loads. Distorted waveforms define PF in another way.
So, dpc (the guy that first answered the OP) gave a complete and correct answer. No need to confuse things like you have done. Please do not ruin this great forum by adding misconceptions, downright mistakes and "feelings" about technical facts.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: i need to roughly calculate kwh
In the US, most utilities monitor kWh. Some charge penalties for low PF, with different penalties kicking in at perhaps 95%, 90%, 85%, 80%, etc -- stepped.
I'm not aware of a single US utility that measures kVA (except to apply stepped PF fees) or that bills based on kVAh.
RE: i need to roughly calculate kwh
Nope, sorry, I have to agree with Gunnar. Only dpc's answer fits the question and deserving of that star just for being the first responder. To be honest though, it's an answer right out of every text book on AC Electricity 101, page 2, right after the cute little diagram of a Sine Wave that seems to exist in every version. This wasn't a difficult question people; no need to make it one.
RE: i need to roughly calculate kwh
RE: i need to roughly calculate kwh
Engineers use "good enough" assumptions all the time. We'd never get anything done if we designed everything to 10 significant digits. And for you to state otherwise is just plain inaccurate.
RE: i need to roughly calculate kwh
Clearly there is a big difference between knowing the rated voltage of the line and the voltage needed to calculate kWh :)
He doesn't even seem to have enough info/measurements to calculate instantaneous kW, much less kWh, with any kind of precision needed, unless he thinks his power bill is off by a factor of 2 or 3 times.
RE: i need to roughly calculate kwh
He doesn't need to calculate the bill down to the cent (and any inaccuracy smaller than half a cent is meaningless to everyone concerned). He just needs someone at the utility to take him seriously and say "hmmm, kfoyil, you just might be on to something, we'll take another look at this bill and get back to you". So long as his calc does that, it's good enough.
RE: i need to roughly calculate kwh
Something else to consider: If usage went high one billing period and low the next, or vice versa, it was do to a reading error. This error is self correcting, as one period compensates for the other. The meter continues to increase its register regardless of what the reader wrote down.