Electricity is distributed from electrical substations to neighborhoods at 15,00

Question

Electricity is distributed from electrical substations to neighborhoods at 15,000 V. This is a 60 Hz oscillating (AC) voltage. Neighborhood transformers, seen on utility poles, step this voltage down to the 120 V that is delivered to your house. How many turns does the primary coil on the transformer have if the secondary coil has 100 turns? No energy is lost in an ideal transformer, so the output power P0ut from the secondary coil equals the input power P, to the primary coil. Suppose a neighborhood transformer delivers 250 A at 120 V. What is the current in the 15,000 V line from the substation?

Explanation / Answer

Given :-

V1 = 15000 v

V2 = 120 v

f = 60 Hz

a)

N1 = ?

N2 = 100

V1 / V2 = N1 / N2

N1 = (V1 / V2)*N2

N1 = (15000 v x 100) / (120 v)

N1 = 12500 turns

b)

Pout = Pin

find I1

I1V1 = I2V2

I1 = I2V2 / V1

I1 = (250 x 120) / 15000

I1 = 2 A

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