Hi all,
I'm on 3 phase (3 wires, no neutral) 240V network in Belgium (50Hz). Voltage between phases is 240V. I was looking at the emonTx_CT123_3Phase_Voltage.ino sketch to measure power consumption. I bought 3 CT devices to plug into by arduino shield, but found out that I might only need 2 (using two wattmeter method).
Should I hook up only 2 CT's and one voltage meter? How should I modify the Arduino sketch for this? It seems to assumes 3 phase measurements . Can I remove all references to the 3rd phase and just add up the first two (again according to two meter method)? What to do with the phase shift... use 8 or 17?
Thanks!
Tom.
Re: emonTx_CT123_3Phase_Voltage.ino
If you will be using the '2 wattmeter' method, then you can indeed treat for understanding only one phase as your neutral, and (ideally) measure two voltages and two currents. If the voltages of the two phases measured from the third are always equal (within acceptable limits), then you can use the sketch that stores the voltage readings and re-uses them for the second phase. Unfortunately, '8' and '17' - the number of samples delay, which is a coarse PHASECAL adjustment - are both wrong because the angle between the phases is now only 60°. Try 4. You can remove all the 3rd phase calculations, of course, and reduce the size of the array.
The necessary warning: Although you are treating one phase as neutral for the maths, it is still just as dangerous as it ever was.