A 25kVA 3300230 V 50 Hz single phase transformer draws no lo

Solution

let us start with the data

we have 25kva transformer and voltage rating 3300/230 V

this means supply end voltage is 3300V and load side voltage is 230V

it drags no load current of 15A and consumes 350W when excited on load voltage side

this means we are excited from 230 voltage side and 3300 side is open circuited and no load current and power are measured from the low voltage side

here we need to find no load componets i.e magnetising component I_m and working or core component I_c

No load power

V₀*I₀*Cos pie₀ = 350W

here V₀ = 230V I₀ = 15A

230*15*Cos pie₀ = 350 W

Cos pie₀ = 350/(230*15)

= 0.10144

pie₀ = Cos^-1 (0.10144)

= 1.469 radians

i.e Sin pie₀ = Sin (1.469)

= 0.9948 radians

now magnestising component I_m = I₀ * Sin pie₀

= 15* 0.9948

= 14.922 A

working or core component I_c = I₀ * Cos pie₀

= 15 * 0.10144

= 1.5216A

so finally the two components are currents are I_c = 1.5216A and I_m= 14.922 A