I need to monitor at least 400 amps of power across 3 phases. I need to continuously check how close I am to overloading the panel as we need to get as close to max usage as possible. Is this something that would work? I only saw these 100 amp CT's while we would need ones with at least 400 amps on each phase, are there other ones that are compatible?
High-Amp Commercial 3-Phase Monitoring with emonTx V3
Submitted by Guest on Sun, 01/06/2014 - 21:05»
Re: High-Amp Commercial 3-Phase Monitoring with emonTx V3
Basically, you can use any CT that has a sufficient VA rating with the emonTx V3. The problem is, most CTs seem to be designed or rated for 0.333 V rms output, whereas the emonTx expects 1.1 V rms for maximum resolution and accuracy.
I tend to recommend the Magnelab range, derated to 33%, so if you need a split-core CT, the SCT-2000-000 would seem to be appropriate (1500 A @ 0.333 V should give you 454 A full scale with the emonTx). The burden resistor in the emonTx would need to be changed - this is a SMT component that you would remove, and there is provision for a wire-ended resistor in its place. If you are only interested in current, then you can certainly tailor 3 of the current inputs to suit, and use the "continuous monitoring" sketch as a basis for your own. That sketch is specifically for single phase power measurement as it also measures voltage, but would be a good starting point to customise from.
If you are really interested in power, it becomes a little more difficult as the emonTx is designed for the UK domestic system which is almost invariably single phase. We have sketches that delay the voltage wave so a good approximation to real power in each phase can be calculated, should that be necessary. (But from your question, it would appear that you are only interested in the current drawn.)
Normally the output is by radio to the emonGLCD and/or an emonBase for data logging, but presumably you have some ideas for the type of output you require?
Re: High-Amp Commercial 3-Phase Monitoring with emonTx V3
To me it sounds like the main issue is going to be the fact that I need to monitor commercial 3 phase. I need to be able to phase balance the load since I will be running very close to breaker limits. Certain sources of electrical load can be network controlled and I was thinking of creating an app that will lower the power draw on those devices in response to an electrical load spike. All the commercial devices I've seen seem to be very overpriced and I was hoping for a cheap alternative that would be easy to interface with over the network. I was wondering if it is possible to hook into a rs485 controled CT instead of the weird one emontx uses with a pi or beagleboard.
Re: High-Amp Commercial 3-Phase Monitoring with emonTx V3
Perhaps you could explain to me how you can control a current transformer over RS485? And while you are doing that, explain what is weird about the CT that I recommended?