Question

6. A transformer has an input voltage of 120 V(rms) AC with an output of 12,000 V(rms) AC . The number of wire turns in the primary is 75. An output power of 245 W is required. Assume the transformer is approximately 100% efficient. Find the

a. Number of wire turns needed on the output side.

b. input current

c. Output current

Answer 1

Input voltage V = 120 volt

Out put voltage V ' = 12000 volt

Primary truns N = 75

Output power P ' = 245 W

a). Number of wire turns needed on the output side N ' = ?

We know N ' / N = V ' / V

N ' = (V ' / V ) N

= 100 N = 100(75 ) = 7500

b). input current i = ?

V / V ' = N / N '

(P/i) /(P ' / i ' ) = N / N '

it is 100 % ,So, P = P '

So, i ' / i = N / N '

Where i ' = P ' / V ' = 245 / 12000

So, i = i ' ( N ' / N )

= (245/12000) (100)

= 245/120

= 2.041 A

c). Output current i ' = P ' / V ' = 245 / 12000 = 0.0204 A