Which products to measure usage of 3 phase machinery?

I am looking for an energy monitoring system that can be used to monitor energy usage of injection moulding machines,

I have 30 machines that draw between 30a - 275a / 3 phase @ 230/400v. Electric motor running hydraulic pumps and large wattage heater elements.
I would need a station for each machine that could transmit back to a base station that can collate and display the usage for each machine on a single web page / portal.
I have already implemented Raspberry pi’s to each machine which are monitoring machine usage stats and cycle times and require a separate rpi type system to mount in the control cabinet of each machine which can monitor the energy usage of the machine incomer.

Please could you give me some guidance on how i could achieve this goal utilising the OpenEnergyMonitor system.

Thanks for looking.
(UK Based)

Is the motor 3-phase, and are the heaters 3-phase? Does that leave only the controls as a single-phase load (per machine)?

Which begs the question: If that’s the case and the load is well-balanced, can you tolerate the inaccuracy of ignoring the power drawn by the controls? - my guess is you can. Given that, you only need to measure a single phase and multiply by 3. If you can do that, an emonPi will do all you want locally to the machine, and serve up the web page via your LAN (I’m assuming that’s what you mean by “transmit”, and not radio?). You could probably integrate that with the monitoring that you’ve already implemented. I’m not a RPi expert, so others can better advise you on that. If this looks attractive and you’re talking 30-off, it might be worth asking the shop if they’ll sell you the 2 current +1 voltage emonTx front-end that’s inside our emonPi.

If your load isn’t balanced across the 3 phases, then you need an emonTx per machine, and the 3-phase sketch. This can feed serially into your RPi (exactly as is done inside the emonPi) and run emonCMS on that, or you can add another dedicated RPi running emonCMS.

You can use our ‘shop’ c.t’s for the smaller machines, but you’ll need a larger c.t. for those that draw more than 100 A. The “emonTx in N.America” page gives details of large c.t’s that are suitable. Most, but not all, require a simple change of the c.t’s burden resistor in the emonPi or emonTx.

Thank you for the reply Robert.

You are correct in that the motor and heaters are both 3 phase. The controls on most of our machines are run from an internal 3 phase transformer that drops the voltage down to 24v. This means the load is well-balanced and i feel any minor variations we can tolerate.

I would be looking at doing 30 machines at one location then another 17 machines at a remote site.
Is the emonTx you mentioned, the version shown in the shop ?
It appears that it would be more cost effective to have an emonTx fitted to each of the machines and then they talk to a single emonBase. Would that setup work.
I would be looking at doing 30 machines at one location then another 17 machines at a remote site.

With regards to the data that is collected, am i correct in saying it is stored in a mysql database that we could then be able to query in order to display usage data within our current machine monitoring system.



You have a problem there with the RF library that we use - JeeLib. It can only cater for exactly 30 “nodes” - and normally one of those is the base station. As the base will never need to transmit, you might be OK with 30, but if you add a machine, it gets difficult. All use the same radio frequency so with 30 transmitting, it’s likely that there will be some collisions in the radio spectrum and data will be lost. It would work, but I’d have some hesitation in saying that it would work faultlessly. How do your existing RPi’s send their data back?

No, by default it is set up for a custom database that’s optimised for the job. I think you can swap to MySQL, but Paul (@pb66) is probably best placed to confirm that.

By default emoncms does use phpfina, a custom data series flat file. As @Robert.Wall says, you can use MySql if that’s your preference or application dictates. To use MySQL it is recommended to steer clear of running emoncms on an SD card, you could add a hdd to a raspberry pi or use something else completely eg a hosted VM. Whith the amount of data you might have coming in from all the machines it might not be a bad idea to avoid using an SD card only setup either way.

Are all 30 machines in close proximity? you may be able to split the 30 into smaller groups and have more than one base.

Is there a specific reason it needs to be a separate rpi? or do you consider the emonTx(s) to be that separate device? Rather than use RF for the emonTx’s you could connect them using the RPi GPIO’s (if only 1 emonTx per machine) or via USB-serial adapters, assuming you RPi’s are networked of course. emonHub can be installed to each exisiting RPi to handle collating and forwarding the emontx data to emoncms.

Depending on how your other stats are collated you might be able to send that data to emoncms to so you have all the data in one place.