Answer:
a) 1.2
b) 0.833
c) 0.694
Explanation:
a ) The transformer steps up the voltage from 12000 V to 425000 V . Voltage in primary is 12000 V and in the secondary it is 425000 V in old transformer
If n₁ be no of turns in primary coil and n₂ be no of turns in secondary coils
the formula is
n₂ / n₁ = voltage in secondary / voltage in primary
n₂ / n₁ = 425000 / 12000
ratio of turns in old transformer
= 35.42
ratio of turns in new transformer
n₃ / n₁ = 510 / 12 ( n₃ is no of turns in the secondary of new transformer )
= 42.5
T he ratio of turns in the new secondary compared with the old secondary
n₃ / n₂ = 42.5 / 35.42
= 1.2
b ) Current in secondary / current in primary
= turns in primary / turns in secondary
current output ratio of old
= Current in secondary / current in primary
= n₁ / n₂
= 12 / 425
= .0282
current output ratio of new
= Current in secondary / current in primary
= n₁ / n₃
= 12 / 510
= .0235
The ratio of new current output to old output (at 425 kV) for the same power
= .0235 / .0282
= .833
c ) power loss in new
= (current in secondary )² x resistance of secondary
=( .0235 x current in primary )² x R
= 5.52 X 10⁻⁴ X ( current in primary )² x R
power loss in old
= (current in secondary )² x resistance of secondary
=( .0282 x current in primary )² x R
= 7.95 X 10⁻⁴ X ( current in primary )² x R
ratio of new line power loss to old
= 5.52 / 7.95
= .694
