Hi all. Long time user of the emon platform.
My old system consisted of 2 emontx v2 radio sensors each with 3 ct sensors and 1 ac sensor.
I’m now in a new location which has 3phase power and a 10kw solar pv array.
I’m looking to build a new system for this located in Australia.
From my current research. I can’t use a single phase ac measurement due to the phases being quite different in voltage.
So I’ve arrived at 2 options
3x emontx V3… On each unit measure an ac phase plus the pv side and the grid power via ct
Or
3x emontx arduino shields setup in the same method as the emontx V3 and transmit radio back to a raspberry pi shield
Am I missing any options?
Is my line of reasoning sound?
I think your line of reasoning is sound. Having only one a.c. input, the emonTx must “guess” the voltages of the other two phases. If they’re different, your power readings will be wrong. Therefore, you must treat what you have as three single-phase systems.
You don’t say what you’re doing with the data?
What radio frequency is your old system?
How is your PV connected - star or delta? (i.e. is it really 3 × single-phase inverters in one box, or a genuine 3-phase? My bet is on 3 × single-phase.)
A few suggestions:
One emonTx V3 plus your old emonTx V2s. (RF freq’s permitting)
an emonPi plus your old emonTx V2s. (RF freq’s permitting)
an emonPi plus two V3s
Convert your old emonTx V2s with a DIY “outboard” extender pcb carrying two voltage inputs, using the spare ADC channels.
A DIY emonTx or emonTx Shield with 3 voltage, 6 current inputs?
Did you mean 3 emonTx Shields all on one Arduino? I don’t think you can do that.
But you can stack 3 emonTx V2s (if you can source a third one) - Full-fat 3-phase monitor | Archived Forum
My 3-phase PCB supports 3 voltage measurements (one on each phase) and three measurements of current. This “uses up” all of the analog IO ports on the Almel 328 processor.
This hardware is primarily indended for diverting surplus power to one or more dump loads. It can equally well be used to monitor power in a 3-phase environment. A kit of parts is available via my Shop page (£50 including the RF module, plus postage).
Can you clarify when you say, “phases being quite different in voltage,” you mean that each phase has a different Vrms? Or are the Vrms amplitudes actually the same, it’s just that they are not aligned in phase?
The calibration constants in cal.h can be set to IPH1=-120 and IPH2=-240 degrees , to rotate two of the phases into alignment with IPH0. As long as Vrms for phases 0,1,2 are equal, it should be fine.