Lab Experiment: 3.b
Programs on transformer regulation
Example 1: The primary winding of a 500VA, 10:1 single-phase step-down transformer is fed
from a constant 240Vrms supply. Calculate the percentage regulation of the transformer when
connected to an impedance of 1.1Ω
Solution:
p = 500 VA
Turns ratio = 10:1
Vp = 240 V
Zs = 1.1 Ohms
To find % regulation
Vp/Vs = Np/Ns
Vs = Vp*Ns / Np = 240 * 1 / 10 = 24 V
Therefore, Vsno-load = 24 V
P = V2S / Z
Vs = sqrt (p * Z) = sqrt (500*1.1) = 23.45 V
Therefore, Vsfull-load = 23.45 V
% Regulation = (Vsno-load – Vsfull-load / Vsno-load) * 100 %
% Regulation = (24 – 23.45) / 24 = 0.229 * 100% = 2.29%
Then the percentage down regulation calculated for the transformer is given as: 2.29%
Matlab Program:
p = 500; % in VA
% turns ratio N1:N2 = 10:1
Np= 10;
Ns= 1;
Vp = 240; % Primary Voltage
Zs = 1.1; % Secondary impedance in Ohms
disp('To find % regulation');
% formula used: Vp/Vs = Np/Ns
Vsnl=(Vp*Ns) / Np;
disp('Vsno-load');
disp(Vsnl);
Vsfl = sqrt(p*Zs); % P = Vs^2 / Zs;
disp('Vsfull-load');
disp(Vsfl);
disp('% Regulation');
perReg = (Vsnl - Vsfl) / Vsnl *100;
disp(perReg);
Matlab Output: