# AC Machines & Devices

Discussion in 'Homework Help' started by zionic911, Jun 23, 2004.

1. ### zionic911 Thread Starter New Member

Jun 23, 2004
3
0
Q.1.
A step down transformer used in a community was found to develope a short Circuit fault. derive an expression for thee short circuit impedance of the transformer.

Q.2.
State 5 conditions that must be satisfied by transformers in parallel

Q.3.
11/0.45kv, 100kva, single phase transformer with the resistance of 20 ohms and 0.1 ohms in the high and low voltage windings respectively. it has iron (fe) losses of 200w. find the equivalent resistance and reactance reffered to the primary and hence the total impedance reffered to the primary.

Q.4.
Find the efficiency of a transformer at the power factor of 0.6, 0.8 and unity (1).

2. ### mozikluv AAC Fanatic!

Jan 22, 2004
1,437
1
hi,

why are the 4 queries not replied up to now. maybe because the answer is found in the books?

here's the formula to compute the efficiency

efficiency = Power output / (Power output + Core loss + Copper loss)

this formula is at the transformer project in the project forum.