Transformer

%Design a 25KVA, 11000/433v, 50Hz, delta/star, core type, oil immersed %natural cooled distribution transformer.The transformer is provided with %tapping + 2.5 + 5% on the h.v. winding. Maximum temp rise not to exceed %45'c with mean temp rise of oil 35'c. %CORE DESIGN k=input('enter the value of k: '); q=input('KVA rating of transformer'); Et=k*sqrt(q) f=input('enter the value of frequency: '); disp('flux of core') %f is the frequency phic=Et/(4.44*f) %phi is the flux per pole Bm=1; %Bm is the mean flux density A=phic/Bm %A is net iron area disp('diameter of the circumscribing circle is : ') d=sqrt(A/.56) %d1 is the diameter of circumscribing circle %width of dimension theta=0.548; a=d*cos(theta) b=d*sin(theta)

%theta is angle in radian

%WINDOW DESIGN Kv=input('enter the value of high voltage winding in KV :'); Kw=8/(30+Kv) Js=2.3*10^(6); %j is the current density Aw=(q*10^3)/(3.33*f*Bm*Kw*Js*A) %Hw/Ww= 2.5 Ww=sqrt(Aw/2.5) %width of the window Hw=2.5*Ww %height of the window D=Ww+d %distance between adjacent core centres %YOKE DESIGN phiy=phic/(1.2*A) Ay=1.2*A Ag=Ay/.9 Dy=a Hy=Ag/a %OVERALL DIMENSION OF FRAME% H=Hw+(2*Hy) W=2*D+a Dy=a %lv Winding% disp('**************low voltage winding*********') Vs=input('enter the secondary side voltage in volts');

%height of frame %Width of frame %Depth of yoke=depth of frame

Vph=Vs/sqrt(3) Ts=Vph/Et Is=(q*(10^3))/(3*Vph) as=Is/Js ab=7.0*2.2*10^(-6) Cd=7.5*2.7*10^(-6) t=38 Lcs=t*7.5*10^(-3) min_c=(Hw-Lcs)/2 n=3 bs=(n*2.7*10^(-3))+(2*.5*10^(-3)) dintlv=d+(2*1.5*10^(-3)) dextlv=dintlv+2*bs

%star connected %turns per phase %secondary phase current %area of secondary conductor %conductor diameter because of paper insulation %no. of secondary turns %axial depth of the conductor %no. of layers %radial depth of Lv winding

%HV winding disp('**********************HV WINDING**********************') Vp=input('Enter the primary side voltage in volts') Tp=(Vp*Ts)/Vph Tp_new=1.05*Tp % 5% tappings Vc=Vp/8 %Voltage per coil Tc=Tp_new/8 %Turns per coil Ip=(q*10^3)/(3*Vp) %HV winding phase current Jp=2.4*10^6 %Current density Ap=Ip/Jp %Area of the hv conductor dp=sqrt((4/pi)*Ap) %diameter of bare conductors di=.805*(10^(-3)) %insulated diameter Tl=28 %Turns per layer Ad=Tl*di %Axial depth of one coil Lcp=(8*Ad)+(40*10^(-3)) %Axial length of one coil i=0.3*10^(-3) %insulation used between layers Rd=(24*di)+(23*i) %Radial depth of each coil dinthv=dextlv+(2*15*10^(-3)) %internal diameter of hv winding dexthv=dinthv+(2*Rd) %outside diameter of hv winding %Resistance disp('******************RESISTANCE******************') dmeanhv=(dinthv+dexthv)/2 %mean diameter of hv winding Lmtp=pi*dmeanhv %mean turn of hv winding rp=(Tp*.021*10^(-6)*Lmtp)/Ap %Resistance of primary winding at 75'C dmeanlv=(dextlv+dintlv)/2 %mean diameter of lv winding Lmts=pi*dmeanlv %length of mean turn of secondary winding rs=(Ts*.021*10^(-6)*Lmts)/as %resistance of secondary winding at 75'C Rp=rp+(Tp/Ts)^2*rs %total resistance referred to hv side pur=Ip*Rp/Vp %per unit resistance of transformer %LEAKAGE REACTANCE%

disp('************leakage reactance*************') mean_dia=(dintlv+dexthv)/2 Lmt=3.141*mean_dia Lc=(Lcs+Lcp)/2 Xp=2*3.141*f*4*3.141*10^(-7)*Tp*Tp*(Lmt/Lc)*(.015+((Rd+bs)/3)) purl=(Ip*Xp)/Vp puz=sqrt(pur^2+purl^2) %REGULATION pu_reg=(pur*.8)+(purl*.6) %LOSSES disp('*********************losses*************') i2r_loss=3*Ip^2*Rp i2r_loss_total=1.15*i2r_loss Wl=3*.3*.010135*7.6*10^3%taking density of lamination as 7.6*10^3% core_loss_limb=Wl*1.2 Wyoke=2*.624*.01216*7.6*10^3 core_loss_yoke=Wyoke*.85 t_coreloss=core_loss_limb+core_loss_yoke %EFFICIENCY disp('************EFFICIENCY**********') t_loss=t_coreloss+i2r_loss_total eff=(q*10^3)/(q*10^3+t_loss) %No load Current disp('*************no load current**************8') atc=120 aty=80 t_mmf=3*atc*.3+2*aty*.624 mmf_ph=t_mmf/3 Im=mmf_ph/((sqrt(2)*Tp)) Il=t_coreloss/(3*Vp) I_noload=sqrt(Im^2+Il^2) per_of_fullload=(I_noload/Ip)*100 %end