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Homework Help: Detecting Phase sequence with light bulbs/ Short circuit voltage

  1. May 13, 2014 #1
    1. The problem statement, all variables and given/known data
    1) If one is using light bulbs to detect phase sequence then it is wise to connect them in series with circuit resistor. Why ?

    2) There is short circuit in phase "A". In which case is short circuit voltage larger, in four-drive (?) system or in three-drive (?) system ? Which system is cheaper ?

    3. The attempt at a solution

    1) Because otherwise light bulbs would have same brightness ?

    Any help would be much appreciated.
  2. jcsd
  3. May 13, 2014 #2


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    Staff: Mentor

    Hi ESSVE. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    (1) probably is referring to using light bulbs as an indicator of phase difference when trying to synchronize a 3 phase synchronous motor with the 3 phase mains.

    (2) probably refers to there being a short-circuit in phase A winding of a motor. But I don't understand the rest of the question.
    Last edited by a moderator: May 6, 2017
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