Three single-phase, 10-kVA, 2400/120-V, 60-Hz transformers are connected to a three-phase, 4160/208-V transformer bank. The equivalent impedance of each single-phase transformer referred to the primary side is 10 + j25 Ω. The transformer bank delivers 27 kW at 208 V and 0.9 power factor leading.

a. Draw the three-phase schematic diagram showing the transformer connection. Draw a per-phase equivalent circuit.
b. Determine the primary current and power factor.
c. Determine the primary voltage.
d. Determine the voltage regulation.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.