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  • Users: VLFit
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  1. VLFit

    VLF not in IEC 63026?

    I just read IEC 63026 and can't find any reference to VLF withstand testing nor using VLF for TD and PD testing. Am I missing it or did they exclude it in the 2019 version?
  2. VLFit

    Low PD High Voltage Transformer Design

    Does anyone know of any good books or articles on the methods to design PD free transformers, up to maybe 100 kVac?
  3. VLFit

    Motor starting currents. Utility input power considerations when

    Using a Motor Test Set with many reduced voltage taps. Utility worried about inrush on a 5000 HP, 12470V motor. Since we will be starting at lower voltages and working up, there will be no full v online starting currents. When will my max current occur? Need they worry?
  4. VLFit

    IEEE Std. 286-2000 VLF?

    Is this standard under review for an update. Will the new version include the use of VLF 0.10 Hz frequency for tan delta/power factor testing?
  5. VLFit

    HV Capacitor Design Resource

    Can anyone recommend a book or other materials to teach the design of oil insulated high voltage capacitors used in charge/discharge applications like thumpers/cable testers, energy pulse supplies, etc. Typical ratings are 10-20 kVdc @ 500J - 2000J.
  6. VLFit

    >100 kVac design of HV tanks up to 100 kVA.

    Looking for company/consultant with design experience in high voltage AC supplies, particularly transformer design for low PD output. Also, bushing design for the same.
  7. VLFit

    Siemens HV Motor data

    Any Siemens people out there to help? I am trying to find out the capacitance of a large HV motor so that we can size the power required from and AC hipot to perform overvoltage testing. I have the nameplate data.
  8. VLFit

    HV Transformer Design for Low PD

    Can anyone recommend one or more books for the design of high voltage, oil immersed transformers, particularly the design and processing steps necessary for low pd output. Thank you.
  9. VLFit

    Voltage Rating of Kraft Transformer Insulating Paper vs Kraft Diamond Epoxy Paper

    In terms of volts/mil, are these two equal in their voltage ratings. When oil soaked following a full vpi and when not soaked.
  10. VLFit

    PD and TD testing motors and generators - what to use?

    Finding the right AC hipot needed to apply the voltage in easy, but what vendors supply a reasonably priced PD measurement device for elevated voltage off-line testing? Same for a Tan Delta device.
  11. VLFit

    Transformer Design Source for High Voltage, Low PD AC Supplies.

    Besides attending coil winding shows, which are excellent sources for info, does anyone have any recommendations for education for how to design and fabricate high voltage test equipment transformers, up to maybe 400 kVac @ 1 - 100 kVA?
  12. VLFit

    Substation Test Equipment

    Is anyone familiar with the High Test Technology products from the UK? They appear to be well made and are attractive and designed similarly to the old Vanguard line.
  13. VLFit

    DC hipots always negative output

    Looking for a concise, ease to understand reason why most all DC hipots are negative output. Thank you
  14. VLFit

    Motor & Generator Winding Capacitance

    Hello All, Does anyone know of a table that shows common motor sizes and the average capacitance from the terminals to ground, particularly for stator windings? I am aware of the many influences on this and the impracticality of my question, but I just thought I would ask if there is some...
  15. VLFit

    72.5 kV Vacuum Bottle Switchgear Testing

    AC Withstand testing 72 kV vacuum sg. The test voltage is 160 kVac (factory or field?) Can someone tell me the expected current draw at that test voltage? We have to purchase >160 kVac hipots but need the kVA rating needed. Thank you.
  16. VLFit

    Power Cable Partial Breakage Test. How?

    Some countries cable testing standards for Mining applications call for a "partial breakage" test of the conductor. A 10% breakage, or deterioration must be measurable. What instrument is or can be used for this test? A resistance measurement won't work, using the Ohm Check Concentric Neutral...
  17. VLFit

    Power Cable Partial Breakage Test

    Some countries cable testing standards for Mining applications call for a "partial breakage" test of the conductor. A 10% breakage, or deterioration must be measurable. What instrument is or can be used for this test? A resistance measurement won't work, using the Ohm Check Concentric Neutral...
  18. VLFit

    MV Cable Fault Locating in Mines

    MV Cable Fault Locating & Testing. Question: When medium voltage cable testing using thumpers or surge generators in mining environments, are there regulations for the maximum joules of energy that can be used to arc the cable fault to help find it? What is commonly used for fault locating and...
  19. VLFit

    Motor/Generator Winding Capacitance's for AC Hipoting

    To calculate the power required from an AC Dielectric Test Set one must know the capacitance of the load. Simply listing the electrical specs of the machine does not reveal the capacitance to permit the use of A=(2pif)CV to calculate the current required at the test voltage required. Is there...
  20. VLFit

    Low PD Magnet Wire Choice for HV Transformers

    When designing low PD high voltage transformers, the turn to turn voltage can't be too high and risk shorted or pd noisy turn to turn flaws. Temperature ratings aside for this question, which round and square magnet copper wire coating has the higher dielectric strength to minimize any possible...

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