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  • Users: Audun
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  1. Audun

    Three phase voltage level in US.

    What is the "normal" three phase voltage in the US ? 440V, 460V or 480V ?? Offshore is normally 440V but motors made in US are 460V and someone claims 480V. Do you use 460V motors as a standard? Since I'm in Europe I have no clue, but need the info.... Audun
  2. Audun

    Measure negative sequence currents.

    I know there is a way of using passive components, and this is what I want. I don't have the book dpc refers to, so please describe it in detail... Audun
  3. Audun

    Measure negative sequence currents.

    I'm wondering if anybody has a setup for measuring negative sequence currents. (using 5A CTs) Anything analoge, not digital please. Audun
  4. Audun

    System fault levels

    I think I will interpret as follws. Fault make: Subtransient short circuit current. Fault break: Transient short circuit current. If anybody thinks this is wrong, please let me know. Audun
  5. Audun

    System fault levels

    The levels is indicated in a technical project description. 2.0 Electrical supply system and tolerances ..... ... 2.3 Fault levels * 13.8 kV System - Fault make, 1.5kA, Fault break 1.0 kA * 440 V System - Fault make, 25 kA , Fault Break 1.7 kA As you can see, it is not in a breaker spec, but...
  6. Audun

    System fault levels

    What does "fault make", and "fault break" represent when indicated for a systems fault levels. I'm only used to transient and subtransient short circuit currents. For a breaker I know what make and break levels indicate, but I have never before seen it used for system levels...
  7. Audun

    Neutral connection systems ITAN and ITSN

    What is the difference between those two ? Audun
  8. Audun

    SF6, critical temp

    What happens to SF6 above 45.6 deg.C, since this is stated as a critical temp for use in a SF6 CB? Audun
  9. Audun

    Unbalanced load/negative sequence currents.

    That is probably right. The damping windings will induce current and work against the contrarotating field ensuring less induction/eddy currents in the rotor metal. Maybe the current in the damping windings don't cause as much heat as the eddy currents would do. Audun
  10. Audun

    Unbalanced load/negative sequence currents.

    The permanent magnet rotor is to my understanding just a separate feeder for the main magneticing circuit.(or else there would not be possible to have voltage regulation) How this helps on the heating problem is what I don't understand. The main rotor still have to have field windings. Maybe the...
  11. Audun

    Unbalanced load/negative sequence currents.

    Hi folks. I have tried to find what recomondations there are regarding negative sequence currents in generators. Standards state max 10% of rated current, but Aggreko told me their rental gen.sets could handle 33% negative sequence currents. When I asked why they differ from the standards, they...
  12. Audun

    Synchronous generator short-circuit current

    Since I had a datasheet beside me, here you are... Typical syncronous generator data: Voltage: 480 V threephase PF = 0.8 Power = 1150 kVA Freq. = 60Hz X'd = 0.157 p.u X''d = 0.122 p.u Xq = 1.210 p.u T'd = 0.132 sec. T''d = 0.010 sec. Audun
  13. Audun

    Insulation thickness XLPE and EP-rubber

    Is insulation thickness the same for XLPE and EP-rubber for same voltage rating ? Audun
  14. Audun

    Unsymmetrical generator load.

    Hi What guidlines do you know regarding unsymmetrical threephase generator load. My question relates to the following case: 480V diesel generator. Load currents for phases are approx. 2000 A, 2800 A, 800 A PF=0.8 What generator rating is recomended. I think there are som production standards...

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