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  1. #81
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    Default Re: Motors for small production machine.

    Oops, forgot one:
    (8) 120kW solid state starter panels
    (0) filters
    https://www.cnczone.com/forums/attac...d=457284&stc=1
    (Not quite as relevant, I don't think they have a DC bus, but still, nonlinear current draw with nasty DV/DT)

    Attached Thumbnails Attached Thumbnails Motors for small production machine.-20210124_103925-jpg  


  2. #82
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    Default Re: Motors for small production machine.

    As strantor said, basically.

    My rw example.
    13 kW 3-phase power, 240V, EU, with 220V single phase upto 5 kW if I choose to wire a single device to the main panel (that I can legally do here, at will (as an engineer with electrical competence)).

    My biggest servo 2.5 kW continuous, does not take a large inrush current.
    It´s modern, and as such does a soft-start via some form of electronic commutation.
    It´s the larger lathe spindle motor, c axis, with 1:3 x 10.000 counts == 0.01 degrees resolution on spindle rotation.

    So it will input about 2.5 kW ++ say 3 kW and output 2.5 kW till the cows come home.
    And peak 7.5 kW output partly from internal capacitors and probably mostly as a mains peak near 8 kW or less (but lasting only a fraction of a second, a second at most).
    Haven´t measured it.

    The 2.2 kW Hitachi VFD is oldish, but higher-quality vs many older units, and soft starts and outputs whatever you set it to upto 2.2 kW continuous, and the peak output is something you can setup in the parameters.

    Within my 13 kW continuous power, a 7-8 kW peak is absolutely a non-issue.
    Any old washing machine, water heater, dishwasher or similar can easily do a 7 kW peak (again, 1 second or less, +/-) for a nominal 2-3 kW trypical heater coil.

    A 13 kW power rating for the installation will easily deliver 3x rated power for a peak, and 2x for a few seconds, at need.
    A 7-8 kW peak even from 2 simultaneous peaks from 2 devices will not affect the voltage of the mains current, in typical installations, in Spain, or Finland, or most of the EU.

    My 13 kW power is much higher than most of my neighbours, who usually have 5-8 kW.
    This is because the base power capacity rating is quite expensive per month - but install is free or nearly so.

    So *everyone* on our street and this power line has technically the exact same 3-phase capacity - probably somewhere around 200+ kW.
    Or perhaps quite a bit more.
    And shared by maybe 20 houses, perhaps more, even much more, like 100 installations.
    The *grid* shares the load, but ones capacity to tap that load is limited by what you pay to the power company.
    And their fuses limit what you can access at peak.
    The incoming cable is exactly the same size for everyone.
    They just re-built the cables last summer, really clear to see.
    Same cables go to every meter, from the power company.
    All the same 3-phase.

    So whatever noise, reactance, inductance or whatever my puny, tiny, servo or VFD might inject into the grid is
    1. shared across 20-100 installations, almost-all with lots of tiny inductive dampers like endless transformers in TV´s, cell-phone chargers, and the like.
    2. attenuated by several hundred meters of power cables acting like dampers aka inducters, due to the length of the (very big) power cables from the power company
    3. measured against a capacity of maybe 1MW - 2 MW of peak current on a continuous load of 200 kW++ before damage
    Any noise and or power effects from small sub-10 kW servos or VFDs will totall disappeary in this large damped mass with thousand+ tiny transformers

    Example 2:
    The VFD effects on the power grid come into their own on industrial installations.
    When we built the HAAS Spain HFO HQ in Montcada, Barcelona, our AC was rated about 25 kW max, for 100-150 kW iirc total capacity, and 50 kW peak single drop for a machine.
    I was the boss.
    The 25 kW was a significant load, and our total load was more than the power company wanted to install - but they had charged us for and had contracted to deliver.
    The power company is obliged to deliver -- but may charge for "stuff".
    They charged us and we paid - but they did not want to deliver.

    Ie. They charged us for it, we paid it, we did all installations to code, but they did not want to install their secondary substation bits for us.
    Their own bits were expensive, about 50k€ iirc, and they could not legally charge us for them.

    It cost us over 100k€ for our power installations - and they still did not deliver the power they are obliged to deliver and we had paid for.
    We ran 3 months on a 50 kW genset 24x7.
    I then forced a political solution, and they fixed the issue in 2 weeks.


    The HAAS spindle motors are essentially VFDs with 3 phase motors.

    At the time, 2011-2013, the change was happening to simplify the range,
    increase reliability,
    reduce parts counts.
    increase availability.
    So from 35 different spindle motors / VFDs the cut was down to 13,
    .. and probably to much less today -- that I don´t know about.

    Because it is cheaper to build a lot of 40 HP // 25 kW VFDs than a wide range of 9- 11- 15 kW VFDs, as the parts cost is a tiny fraction of the real cost.
    So machines with theoretical 12 kW spindles like a DT-1 actually have / had a 40 HP / 25 kW VFD inside them.
    And they are definitely gonna last ==forever if only 12 kW peak is taken out of them, with components rated for 25 kW continuous.

    And they are cheaper to make, in great scale, than small quantities of VFDs for various small machines, about 60 different models.
    And vastly easier to stock, service, and maintain a single universal VFD (or a few VFD models) than 30 different models.

    In the industrial use, our 30-50kW typical draw was very significant.
    Because we needed ac AND big heavy machines with 25 kW each (draw, theory) , and we had 7 of them connected.
    50 kW was marginal for our use, barely able to do AC at cold times and a very few machines, with limited performance.

    HTH -
    It´s a wide crosscut of real jobshop and industrial power usage, need, and costs.



  3. #83
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    Default Re: Motors for small production machine.

    Your stories about the power company don't sound fun. I spent some time in Spain (~2007) and while there I noticed most homes have a solar array on top, and maybe a solar water heater. I wondered if this was because of high electricity cost. Now I wonder if maybe because of unreliable electricity providers. Or is it both?



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