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  1. Skokian

    Adding short circuit on closed transfer?

    There may be ground fault trip considerations. Also, does the generator have synchronism capabilities to prevent out of phase connection to the grid thru the 1000 KVA transformer. Is this a medical facility? The ATS mfr. can lend guidance. I'm familiar most with Zenith/GE, Russelectric...
  2. Skokian

    starting a 700 kw with a VFD of 180 kw

    You have to be very careful to connect the motor in phase with the line voltage, or close to it to avoid a large switching transient due to the motor back EMF which will be around 85% of the line voltage if the motor is up to speed. For starting an unloaded motor, you may be better off with a...
  3. Skokian

    4160 VOLT MOTOR RUNNING @ 480 VOLT?

    The starting current is down by the voltage ration, the load poriton of the running current is increased by the voltage ratio. The no load current is mostly inductive, and mostly saturation currents. These will be down dramatically with lower applied voltage, expecially the first 20% or 30%...
  4. Skokian

    Star Delta starter on 550 hp motor - 480 volt

    Is this an "open transition" (three step) or a closed transition (four step) starter? With open transition, if the motor does not get up to speed, or looses speed during the open transition period, there will be a current surge of LRA (LRC) plus offset on one or two phase currents for a few...
  5. Skokian

    VFD Causing Bearing Failure

    I don't know if the motor shaft is grounded by the load (pump). E;g.: Is the shaft coupling direct or thru a coupler, and is the coupler, if used, insulating or not. The grounding rings or brushes being sold are not to simply ground (earth) the shaft; but rather, to shunt (bypass) the harmful...
  6. Skokian

    Input Line Reactor

    A line reactor will reduce line current from around 140% of FLA for a standard six pulse VFD to around 105% of FLa or a 5% reactor or a bit higher for a 3% reactor. These reactors also serve to protect the storage capacitors from over-voltage due to line spikes and transients. Note that these...
  7. Skokian

    different currents on the parallel wires of a phase

    Is the motor paralles wound? E.g.: Does the motor have six separate windings? Are the motor windings in Wye (Star) or in Delta? Tx. Regards . . . Jim S. Nasby
  8. Skokian

    can we run the 360 volts, 50Hzs motor on 460volts 60Hzs

    How old is this motor? It may not be wise to run it at the 20% above it's design speed depending on the type of rotor. Is it a squirrel cage motor? Regards . . . Jim S. Nasby

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