Why are the three phases leading and lagging?

Discussion in 'General Electronics Chat' started by foolios, Nov 9, 2009.

  1. foolios

    Thread Starter Active Member

    Feb 4, 2009
    160
    1
    Why do power transmission lines have three phases that are offset by 90 degrees?

    And how does the power generator create three seperate phases like that? I see how the generator is depicted as generating AC but it is only showing one line. Are there 3 coils? Three generators? Three sets of magnets? What gives?

    Thanks in advance
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    They are offset by 120°.
    When you add up the three offsets, you get 360°.
    This should help explain things:
    http://en.wikipedia.org/wiki/Three-phase_electric_power
    Look here, too:
    http://en.wikipedia.org/wiki/Induction_motor
    Generators:
    http://en.wikipedia.org/wiki/Electrical_generator
    Alternators:
    http://en.wikipedia.org/wiki/Alternator
     
    Last edited: Nov 9, 2009
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Each of the three phases is offset with respect to the other two by 120 degrees (leading in one case and lagging in the other) - not 90 degrees.

    The AC generators have three similar windings which are mechanically offset in such a way as to generate the correct sinusoidal voltages with the required phase relationships.

    There will be any number of web links to this subject - try Google.
     
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