KRC4 Smallsize Power Requirements

    Hello guys,


    I would need an advice to clear a doubt i have.


    In the next few months we will probably acquire a KR10 R1420 Cybertech NANO, paired with a KRC4 Smallsize controller


    There won't be any additional axes, only the robot itself.


    I downloaded all documentation I could, and the KRC4 Smallsize specification manual states this power requirements:


    Rated supply voltage AC 3x380 V, AC 3x400 V, AC 3x440 V or AC 3x480 V

    Direct connection with grounded neutral

    Rated supply voltage tolerance ±10%

    Rated connected load 3.30 kVA

    Short circuit current rating 5 kA

    System impedance ≤ 300 mΩ

    Ground leakage current -

    Mains-side fusing 3x 32 A, slow-blowing

    Mains-side fusing without drive box 3x 16 A, slow-blowing

    Mains frequency 49 ... 61 Hz


    So far so good, except that the total power rating of the 6 Robot motors is around 5.11 KW


    I'm quite sure that the Robot will never use all the motors at maximum power at the same time, but anyway I don't understand why the controller seems "underpowered" with only 3.3 KVA


    How much power I have to guarantee in order to be sure that the robot will work properly?


    Thank You for your time

    if manual states 3.3kVA than that is what you should provide for system to operate normally. that indicates rate that energy is taken from mains and placed into intermediate circuit. mains only need to top up capacitors in intermediate circuit for the energy actually used (losses, friction, etc.).


    as mentioned motors are not powered by AC directly, AC is rectified and energy is stored as DC in filtering capacitors. the caps buffer energy for times when motors may demand more than what comes from mains. also none of the axis runs continuously in one direction. axis accelerates, then decelerates all the time. largest motors are on main axes and those CANNOT run continuously due travel limit. so energy is drawn while accelerating (motors working as motors) but it is pumped back into mentioned capacitors when decelerating (motors working as generators).


    btw. voltage on those caps in intermediate circuit is not steady. it fluctuates a lot. if there is not enough energy in intermediate circuit and mains cannot resupply fast enough, robot will not be able to accelerate as much so speeds would be reduced due brownouts. if this performace reduction is significant and exceeds certain trhesholds, system will display appropritate fault messages...


    in fact during deceleration of robot with payload, voltage on caps could reach dangerous levels. to prevent that some of the stored energy may be dumped into balast resistors where it is wasted as a heat.


    btw. if mains are fused with 3x16A and supply is 400VAC then continuos power draw from mains would be up to

    400V * 16A *sqrt(3) = 11kVA. this is over three times more than mentioned 3.3kVA

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

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