I built my own emontx . and was wondering if i can make it usable for a 3phase system . When measuring using the 3 phase voltage sketch it gives back the parameters in separate values. However i want to get a cumulative value for all 3 current transformers . like get just one Irms , pf . and real power. i have been searching through forums and i still cant find it out how to proceed.
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Re: Measure single values from 3phase system
You will not find the answer to that in the forums, because I don't think the question has been asked before. You need to look at the sketch and add the values together in there. Before you add the power factors together, think of the definition and what power factor means.
Re: Measure single values from 3phase system
thanks that gave me something to think about . is it possible to just add all the values .. since they are 120 degrees out of phase . wont the values be correct . Quick Question __ do i need to place a voltage transformer for each line ..
Re: Measure single values from 3phase system
If you followed the emonTx design exactly, there is only provision for one voltage transformer, hence the need to delay the voltage samples so that a good estimate of the real power of phases 2 & 3 can be calculated. If you do have three voltage inputs, there's absolutely no need for that complication and your measurements will potentially be more accurate anyway. If you do go down that route, you could use the "discrete sample" sketch as a basis, sampling each phase in turn, or if you need rather more accurate measurements, you could modify either the 'continuous' sketch or you can look at Robin's 3-phase router (http://openenergymonitor.org/emon/node/1757). The 'continuous' sketch is Robin's in any case - based on his diverter code, but the diverter sketch is probably a better starting point. If you require the separate (or combined) currents, some work will be needed to insert the code to compute the rms value.