trnsformer circuits help

Discussion in 'Homework Help' started by TheSpArK505, Nov 10, 2014.

  1. TheSpArK505

    Thread Starter Member

    Sep 25, 2013
    Hi everyone hope you fine.
    1.I'm studying the auto transformer and i have reached where it says apparent power by conduction and induction ..This the first time i see this question .I'm familiar with the power P=VI..If any one could explain this please?
    see the two attached files one for the question and the other for the answer

    2.the other question is for a three phase transformer .If each single transformer is of 20KVA ..if a three are tied together to form three phase transformer, what is the power that reaches the load if the three of the are configured in delta or wye ??

    waiting for help:(
    Last edited by a moderator: Nov 10, 2014
  2. panic mode

    Senior Member

    Oct 10, 2011
    forget about topology and fact that transformer is wired as autotransformer, just ask yourself what is the transformer power rating... that is the amount of power that is transferred by induction (through transformer). in this case that is 100kVA

    rest of the power is by conduction (bypasses transformer). here that is 1000kVA

    together they produce output power of 1100kVA. this is 11x greater than transformer rating and it is true reason for using autotransformers (small transformer can act as a big transformer if it is used as an autotransformer). the downside is that autotransformers do not offer isolation (which larger transformers can do).

    3 x 20kVA = 60kVA regardless of connection (delta or wye). in one case you get lower voltage but larger currents, in the other you get higher voltage but lower current... end result is power is power (is power...)
  3. TheSpArK505

    Thread Starter Member

    Sep 25, 2013
    but how to calculate power by induction and conduction???
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    Do you understand what is meant by those terms?
  5. TheSpArK505

    Thread Starter Member

    Sep 25, 2013
    actually no?!!:oops: i only know p=vi
  6. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    Read thru this PDF tutorial.