Please kindly help with the solutions to these exam past questions, which I would be used to teach my students who will be writing exams next month
1) In a three-phase four-wire system, the line voltage is 415v and resistive loads of 15KW, 10KW and 5KW are connected between three conductors and the neutral.
Draw the circuit diagram.& calculate the current in each line
2. A 4-KVA, 200/400v, 50Hz single-phase transformer gave the following results in a laboratory test;
Open-circuit test 200V, 0.7A7OW,
Short-circuit test15V, 10A, 80W
a. State the values of the transformer's copper loss on full load and its iron loss
b. Calculate the efficiency of the transformer when supplying its full load at a lagging power factor of 0.8