TRANSFORMER CALCULATIONS

A single phase transformer has 5000 turns on the Primary winding and 1250  turns on the Secondary. Winding resistances are r(1) = 4 ohms and r(2) = 0.25 ohms. Leakage  reactances are x(1) = 16.0 ohms and x(2) = 1.0 ohms . The resistance load Z(2). If applied voltage at the terminals of the primary winding is 1200, find V(2) and the voltage regulation. Neglect magnetising current.

Let 'a' be turns ratio.

a = N(1) /N(2) = 5000/1250 = 4

R(1) = 4 + (0.25)(4)2 = 4+ (0.25*4*4) = 8 ohms
X(1) = 16 + (1)(4)2 = 16+ (1*4*4) = 32 ohms
Z'(2) = 24 (4)2   = 384 ohms



I(1) = 1200/(384 + 8 + j32)    =  1200/393.303954/- 4.6668
                                                      = 3.051075/-4.6668 



aV(2) = I(1)Z'(2)
            = 3.051075/-4.6668    *384  =1171.6129/-4.6668   
V(2)  =  aV(2)/a    =(1171.6129/-4.6668)/4    =  292.90323/-4.6668  


Voltage Regulation Is Given By


[{|V(1)/a| -|V(2)|}/|V(2)|  ] *100%

{(1200/4 ) - 292.9  }/292.9    *  100%


= 2.42% lagging