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Answers Please. Electrical Technology.

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1. A load of 2.5kW takes a current of 12 Amp from a 230 Volt supply. Calculate the power factor.


2. Three single phase loads are to be connected to a three phase supply. All at unity power factor. The loads are,


i, 60 Amp.


ii, 50 Amp.


iii, 40 Amp.


By any method determine the neutral current.


Z.
  • 0
    Just wanted to say thanks all above for the enjoyable exercise; I've been playing with programming in Python lately and (once I'd realised I needed angles in radians not degrees...) it was satisfyingly tidy to use Millman's Theorem on the phasors directly. ?
  • Former Community Member
    0 Former Community Member
    How about drawing out the phasor diagram for the three currents on a piece of graph paper and use a ruler to measure the resultant neutral current to be around 17A at 30 degrees lagging L1? Will it be sufficient to answer the question?
  • 0
    The original post said   -  "By any method determine the neutral current."

    So a diagram should be acceptible and, in fact, would be a quick way of obtaining the answer during an examination.

    Regards

    Geoff Blackwell


  • 0
    GeoffBlackwell:

    The original post said   -  "By any method determine the neutral current."


    I got 150A since my method was to connect all three loads to the same phase........


  • 0
    Err yeees but, no , but ...

    I may have worked on a job where someone did something like that.  It might have been better if 2 of the 3 phases had been isolated prior to power being re-applied after the  fitting of the single phasing strap across the output terminals of the incoming switch.


    The element of shadenfreude as it was clearly not me was unavoidable. Still the electrons did make it very clear which fuses should have been pulled to do the isolation, with a sort of noise emitting diode effect ....

    M.
  • 0
    "noise emitting diode effect "


    ?


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