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  1. jantoffman

    VFDs and impedance matching for cables

    Thanks everyone!
  2. jantoffman

    VFDs and impedance matching for cables

    Currently I'm reading a bunch of documents on power cable selection for VFDs. I kinda understand the potential problem of impedance mismatch, but I'm not sure how to DESIGN around it. Do people actually measure the impedance of their motors before hand and try to match it? There are a lot of...
  3. jantoffman

    Is Pump Runout possible with VFD?

    Am I missing the boat? The problems with pump runout as I understand it, are possible overloading the motor and possible cavitation with resulting vibratation and pump damage due to excessive flow. I'm looking at a system that will be at low head for one step in the process, and high head at...
  4. jantoffman

    Instrument Power 0VDC Referenced to Ground?

    Thanks Henneshoe. Any reason you do it this way? Any Pros / Cons for floating the 24VDC vs grounding it?
  5. jantoffman

    Tank Blanketing - minimum pressure

    Is it reasonable to nitrogen blanket a tank at 1" W.C. ? It seems tight with 1" set on control valve and 1/2" on conservation vent. And these aren't fancy Ostand blanketing / venting valves. 40' x 25' tank with flammable liquid. Does barometric pressure play into this? I.E. if I set the...
  6. jantoffman

    Instrument Power 0VDC Referenced to Ground?

    I'm looking for what is considered best practice as far as referencing the negative (common) side of a 24VDC instrument power system to ground. This is the instrument power (not signal) for 4-wire transmitters (not loop powered transmitters). Are there any pros / cons to doing it? My thought...

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