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  1. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Thank you for your answer! Will a HF noise circuit loop not be created if the ladders are grounded to building PE only? From converter - through the power cable - Induced onto the conductive cable ladder - trough ladder grounding wire - to building ground system - back to the converter PE...
  2. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Thank you Keith for your answer, very informative indeed! When describing the "Own VFD ground screw" Do you mean the "power ground" which it is often named by VFD suppliers? Shouldn't the cable ladder also be grounded to the "Power ground" to offload the HF freq. noise induced in the metal...
  3. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Thank you for your answer Gr8blu! Some very good points. I feel that I have a good understanding of the best practices in this topic. The thing I'm wondering though is, if you fulfill all of the best practices will it ever be too big of an overkill. Shielded cables, PE cable one size larger...
  4. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Makes sense, do you think full size is still needed if shielded cables are implemented?
  5. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Thank you for your answer FacEngrPE. The use of shielded cables is still up for debate, as the pricing increase by almost 50%. But ofc. it is the preferred option. Also i find it hard to argue for shielded cables seeing as it's difficult to predict/calculate the need for it before system...
  6. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Thank you for your answer, So you common thing to do is to trust that the PE cable (1/2 size of the power cables, approximately 150mm2) would function as a sufficient return path? I'am guessing that a well connected and terminated cable tray also adds to this functionality.
  7. Jensdsds

    VFD High Frequency grounding of stator vs. return path via. power cable tray + PE + bare Cu cable

    Hello, In a MV MW system with a VFD driving a motor, how do you handle grounding the High Frequency common mode currents? The rotor has shaft grounding which is grounded to the stator frame. Stator frame is grounded via the PE cable routed in the same cable tray as the power cables. The PE...
  8. Jensdsds

    Selection of voltage level for MV cables

    Gr8blu thank you for the answer. Some good points. And great to get some experience on the topic, seems clear that the system should be designed with optimal care if you want to max out the voltage rating on the cable. Could you give some insights into the meaning of a cable spark test, and...
  9. Jensdsds

    Selection of voltage level for MV cables

    Gr8blu thanks a lot for your detailed answer and shared experience. Your answer corresponds with what I've been hearing from other engineers. It could be great to figure out a way to calculate or show the reasons behind this choice. For an example when you have a 6.6kV system and the converter...
  10. Jensdsds

    Selection of voltage level for MV cables

    Hello, When selecting cable for high current power supplies 500A+, and a specific voltage rating of e.g. 3.3kV. The cable is between a converter and a large motor, so the system will have some switching dv/dT over voltages, but limited by a dv/dt filter. Do you then select a 3,3kV cable or...
  11. Jensdsds

    Heat transfer coefficient change as deltaT change?

    Hello, Thank you all for the answers, it was very informative and helpful. Kind regards - Jens
  12. Jensdsds

    Heat transfer coefficient change as deltaT change?

    Hello, i'm a student in electrical engineering and i'm doing a project using COMSOL multiphysiscs tool to anticipate the temperature of a cable being subjected to a specific current. The test is done in real life and then simulated in COMSOL, to see if its possible to anticipate. Currently we...
  13. Jensdsds

    Changing the way COMSOL calculates the resistance of a conductor

    Hello, Alright, thank you guys for the answers. It's been very helpful! Kind regards - Jens.
  14. Jensdsds

    Changing the way COMSOL calculates the resistance of a conductor

    The resistance problem should be fixed now, calculating a new electrical conductivity value. Thank you
  15. Jensdsds

    Changing the way COMSOL calculates the resistance of a conductor

    Hello, Thank you both for the advice, i will try looking into the solutions. Yes btrueblood you are correct. I intend to keep the same physical parameters for the cable, so that the heat flux matches the real test stand. So my only wish is to correct the resistance of the wire. My study...
  16. Jensdsds

    Changing the way COMSOL calculates the resistance of a conductor

    Hello, I'am doing a Joule heating study of a simple cable model. The cable has a terminal of 50A in one end, and a ground in the other end. A heat flux is added to the surface. My problem is: I am simulating a Stranded cable as a solid cable in comsol for time saving and mesh optimisation...
  17. Jensdsds

    COMSOL startup help

    Hi, thanks you for the answer. The analysis/study is steady state yes. I've added a Heat flux boundary to air with 5 W/m2 to all boundaries except input and output end. A screenshot of this is attached. I have no thermal conditions at the end of the cable yet. I would think that would require...
  18. Jensdsds

    COMSOL startup help

    Hello, this might be a long shot but here we go. I am looking for someone to assist me with some questions about the FEM software COMSOL. Specifically i am creating a single phase cable model which should be able to anticipate temperature rise at diffrent amps through the cable. I've build the...
  19. Jensdsds

    Skin effect in Generator power cables at 120Hz

    Thanks a lot!
  20. Jensdsds

    Center wire for EMC common mode return path

    Hello Marke Thank you very much, for a well explained and detailed answer! It was very useful, i do have some follow up question: [ol 1] I know a project where an engineer installed a center wire in the middle of a single core trefoil setup.(Along with a correctly terminated cable tray)...

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