Hello everyone!
I recently assembled a voltage and current monitor, 127v with AC voltage sensor - ZMPT101B and non-invasive current sensor 100A SCT-013 with consumption accumulator in KW/h. It is working in the test phase. Here in my house the power supply is biphasic + neutral, ie F+F+N, the two phases 220v, neutral phase 127v. I took it through the library
all values for single-phase measurements and I'm doing the sum to accumulate in KW/h. I plan to install it in the power input of my house. However, I have no idea how to do it. As I have F+F+N, I balanced the phases with neutral so as not to overload only one phase. The question is, has anyone ever set up something like this, to give me a hint on how to do the sums, given that I have this balanced network with F+F and F+N connected devices?
For a household, I think it would be accurate enough just to treat the two phases as independent, and add the two kWh values together.
A 220 V appliance drawing from F1+F2 is the same as two identical 110 V appliances (each with half the impedance of the 220 V appliance) drawing from F1+N and F2+N.
Yes yes... and how do I handle load balancing, since, for example, I have a refrigerator, coffee maker at F1+N and washing machine at F1+F2? Assuming... F1 = 6a, F2 = 8a, I think about taking the value F1 x 2 + the current difference, which would be 2a. Was it correct?
Hi, autor of the post that was linked here. I think that whenever you have an 220v apliance, you have the equipament connected between phases, thus the current is not the same as the current that is between neutral and phase one. I may be wrong, but thats how i think. To counter that, i believe the best way is to use three current sensors, one on Phase 1, one on Phase 2 and one on neutral. For measuring purposes, you would calculate F1127v (which is f1+N) and F2127v (F2+ neutral), after that you would just substract from neutral to know how much current js running on these two phases. Because (most likely) its a delta connection, current between phases are equal and most likely will show a angle of 120°.
It makes sense what he said tho, using one sensor on each phase will give you the correct current of thr system, that is because the ARMS that is being drawn is the same, considering the fact that you connect a pure resistive load between those phases, which ill assume that the current itself will be drawn equal from each phase. For phase angle monitoring, k've been maturing an ideia, but for the moment it needs alot of processing, but you can test it, if you want. Connect the two sensors on a Op Amp, do the calculations necessary so it output a 5v whenever the two phases are conducting current. That time less the usual 16,6ms (for a 60HZ supply) is the phase angle delay between the two. Being more specific, you just need to convert it to degrees using a time formula, which is more or less like this: delay x 2pi/ 16,6 (for 60hz supply).
Normally a split phase system would have the phases 180 degrees apart. 120 degrees is for three phase, and the voltage between phases will not be twice the voltage of a single phase.
Remember, You are dealing with a center tapped transformer. Many residential transformers are shared between 2-3 residences. So what you are measuring in your home will include the effects of what your neighbors are using. Not the actual power, of course, but the voltage on each side of the center tap will be effected.
Paul
Yes, this is a real problem. Remember that when measuring power factor, not only will you measure your house, but the others too . Also, most likely that sample will have alot of noise, because of the subfrequencies, reactive and capacitive powers that are being injected into the grid. It os worthy the effort, however, for power quality purposes.
That is the point i make, however, with a 120° phase angle, it is correct to assume that the VRMS and output current of that system will be the same because even being 1/3 different, it is safe to assume that the other one is either behind or ahead, at basically the "same distance".
Easiest way to do that is to measure the VRMS with a true VRMSmulti metter on both phases, then apply a correction factor on the code, i've already done that with a error of 1.3%.
With 220 volt / 127 volt it sounds like you are on two phases of a 3-phase system, instead of the 220 / 110 split phase common in the US. Adding/subtracting the current between phases has to take the phase difference into account. Been too many decades since I worked with 3-phase power, about all I remember is the phase to phase voltage is the phases to ground voltage multiplied by the square root of three.
Yes, that's why I'm using 2 F+N voltage sensors, for reading and calculations. I know it can't be real, but if the result is satisfactory, I'll share it with anyone who wants to assemble.