Beiträge von Borianson

  • Current measurement is incorrect

    Zitat

    Thanks for the (bad) news! Did you open a ticket at Allterco yet?

    We measured the voltage (yellow) and the current (blue) waveform with oscilloscope. The current waveform is not sinusoidal, it has square shape. Probably this cause the problem with calculating the power factor and the current.

    As far as I heard the Analog Devices ADE7880 chip is the core of the Shelly 3EM which is capable of measuring RMS of signals up to 2.8kHz. So theoretically the device should be able to measure well, but I do not understand why it is not working as it should.

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  • Shelly 3 EM Strom über 120 A

    Zitat

    Unfortunately, the measurement result is already wrong from approx. 80A (and completely).

    The "mistake" has already been confirmed by Allterco.

    However, it is not yet clear whether this will be fixed. I'm still discussing this with Dimitar: -o

    Could you please share what was the final conclusion of your discussion with Dimitar?

    I have a problem with a 3EM where I would like to measure ~100As on each phase and it doesn't seem to measure well. 4 other Shellys measuring under 50As are measuring well for us, so it is a strange behaviour.

    Discussion about my problem.

  • Current measurement is incorrect

    Zitat

    Here’s a link to a complaint of a user (unfortunately in German language): Click!

    Thanks a lot! That is not a very good sign. Each one of the other machines are measuring 50As or less and they are working perfectly. I hope my problem will be solved with a device change, because we already bought 25 pcs of EM3. It would not be funny if they state it can measure 120As if in the reality it is maximum 50As.

  • Current measurement is incorrect

    Zitat

    IIRC, we had reports in the forum current could be measured to 50A maximum even with 120A clamps. Don’t remember in what thread this was mentioned…

    This is interesting, because the device is exactly topping out at 50A instead of 120A as it should. I try to find this forum post, but please link that to me if you maxbe find it. Thanks!

  • Current measurement is incorrect

    Zitat

    Assuming there is either no neutral or it is arranged in a separate cable I would gladly know if the power factor (3EM says 0,41) would be plausible? If not, I would recommend to double check the connection of the voltage inputs of the Shelly 3EM: Are they corresponding with the current clamps A, B and C? Incorrect settings are producing generally too low current readings!


    Addendum: My answer was written before you clarified the neutral question! Sorry!

    I double checked the wiring this morning and was perfectly OK. The power factor problem would be understandable, but the measured current itself still should be good independently. (The calculated real power would be of course wrong)

    I measured our other 4 pcs Shelly 3EM all of them are measuring within 1-2% error regarding the current values. The power factors are also close to the nominal 0.85 written on the motors.

    I assume something is wrong with this particular device. I will ask the evening shift electrician to replace to another new one. Tomorrow we will know more.

    Zitat

    I just installed my 3EM. I detected that at the settingspage you can select 50A or 120A transformers. My 3EM was deliverd with 120A transformers but SW was set at 50A.

    Did you check this setting. Would explain a difference of app 50%.

    McM

    That setting is only availible in the old firmwares. I downgraded, and set to 120A and was still measuring wrong. After I upgraded to latest firmware with the exactly same reasults.

  • Current measurement is incorrect

    Dear All,

    We have installed our fifth Shelly 3EM to one of our machine. We are experiencing huge difference in the measured current value compared to our calibrated Fluke current clamp. The calibrated, real current value is almost twice compared to what the shelly shows (96A vs 50A).

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    There is definitely something wrong with the measurement. Can anyone help what is wrong?

    I tried different firmwares all gave the same result.

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  • Total consumption counter and other behaviour

    Hi! We bought a Shelly 3EM, and we like what we experienced, so we would like to buy many more at our company to monitor energy consumption of machines. But before to proceed I have several questions regarding the exact behaviour of the device.

    • What is the maximum/overflow value of "total" energy counter? I would like to be prepared to get this value reset periodically if there is any chance of unexpected behaviour in a reasonable timeframe.
    • Is there a way to reduce the update period of "total" energy counter? It is 1 min by default as far as I see.
    • Am I right if I expect this value to be reset only by an intended command? So the device should not get this value resetted by power-cut, fw update or any other reason.
    • Can we expect any difficuties with multiple devices on the same network? We have a pretty modern and well established network with ~20 brand new Unify APs. I expect maximum 8-10 3EMs on a single AP, totally ~40 pcs.

    Thanks in advance for any helpful comments!