Current in the Neutral

Discussion in 'Homework Help' started by Kayne, Mar 29, 2010.

  1. Kayne

    Thread Starter Active Member

    Mar 19, 2009
    105
    0
    Hi There

    The question I have is the following

    If you have a 4 wire 3 phase system and Ia=20A@.8pf, Ib=5A@.6pf and Ic=0A because of a blown fuse. What is the Neutral current.

    I have found that in an unbalanced system In=Ia+Ib=Ic so knowing this I worked out what In would be for example.

    In=16+j12+3+j4+0
    In=19+j16
    In=24.8@40deg (polar)

    I have the answer which is 16.75@-48.7deg but am unsure how the book come up with this. Am i using an incorrect formula?

    Does anyone know of any good electrical engineering books with examples that have been solved and worked though step by step?

    Thanks
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    The book answer appears to have no relationship to the possible answers.

    As a side note, you need to be careful when quoting power factor. You must indicate whether the particular case is for a leading or lagging power factor condition - rather than just the magnitude of the power factor. Otherwise you will end up with problems in your calculations.

    Regarding a book with worked problem examples you might investigate whether there is a Schaum's Outline in the series which is relevant to your needs.
     
    Kayne likes this.
  3. Kayne

    Thread Starter Active Member

    Mar 19, 2009
    105
    0
    You words I will take on board when quoting power factor.I have been confused to why some question work out and others don't and this is the reason. This will also help in explain the question on sites like these.

    I have found some Schaum's Outline series on the subject and they are on there way, hopefully the worked examples will guide me. The Schaum's Outline series has everything in alot of different categories. This will help me in my coming subjects also.

    Thanks for taking the time to explain this to me.
     
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