# Homework Help: Transformers problem and output voltage

1. Oct 19, 2009

### phys-unit

1. The problem statement, all variables and given/known data

Power is generated at 24 kV at a generating plant located 124 km from a town that requires 40 MW of power at 12 kV. The voltage will be stepped up from 24 kV to some voltage V by a perfect transformer, transmitted over wires, and then stepped down to 12 kV by another perfect transformer. The two transmission lines in between the two transformers each have a resistance of 0.10 /km. What should be the output voltage V of the transformer at the generating plant in order for the overall transmission efficiency to be 98.5%?

a) First determine how much power must be generated at the plant in order to deliver the required power at the town. (Enter your answer to the nearest 0.1 MW.)
1 MW

b) The difference between these two powers is the amount of power that is dissipated by the resistance of the transmission wires. How much power is dissipated during transmission?

c) The next step is to find the total resistance of the two wires.

d) Determine the amount of current flowing through the wires in order to dissipate the power lost during transmission.

e) Finally, use the generated power at the plant, together with the amount of current flowing through the wires, to find the required output voltage V of the transformer at the generating plant.

2. Relevant equations
I think yuo woulsd use the conservation of energy? You might also use Vs/Pv?

3. The attempt at a solution
I got question A: 40.6 I'll continue to look at the others tell I get them.
Question B: .6

Last edited: Oct 19, 2009