Take Window space Factor as: Selecting Current Density: W indow area required by Output Equation:
Kw= d= Aw=
0.3 2.75 A/mm^2 0.11357226 m^2
Selecting Height to Width Ratio as:
Hw/Ww=
2.5
Window Height: Window Width:
Hw= Ww=
0.53285144 m @ 0.21314057 m @
Distance Between Limbs;
D=
455
mm
Taking the Yoke also to be 6 stepped: Height of yoke: Depth Of Yoke:
Hy= Dpth=
230 230
mm mm
Overall Height: Overall Width
H= W=
990 1150
mm mm
530 215
mm mm
WINDING DESIGN:
Total Primary turns Required= Total Secondary turns Required=
Area of conductors:
H.V: L.V:
T(H.V)= T(L.V)=
Actual 5% tap Integral value Taken 773.001206 811.6513 819 17.4459778 18
ah= al=
11.0192837 mm^2 488.245471 mm^2
L.V WINDING DESIGN: Taking Stranded Conductors: Area per Strand is:
Strands= a=
15 32.5496981 mm^2
Selecting a Double Helical Winding , Taking the distribution of each L.V Conductor as: 5 Vertical and 3 horizontal,(Rectangular Conductor) Fr om the Conductor Size data sheet: Dimensions of each Strand is
h= w=
6 5.5
the per strand area is 32.1mm^2,thus modified value of curr ent density:
d'=
2.78852553 A/mm^2
Taking 0.25mm insulation all over Dimension of each strand is:
h'= w'=
6.5 6
mm mm
Therefore Conductor Size is:
Hc= Wc=
32.5 18
mm mm
Thus the L.V Winding comprises of 2 Layers Helicaly Positioned and,
mm mm
9 conductors per layer for a total of 18 conductors, taking 2mm for duct between the 2 layers: Taking space between conductors for cooling a sp=
20
mm
Total Winding Height:= Total Winding Width:=
452.5 38
mm mm
H= W=
Taking 5mm clearance for bakelite former between lv and the core: inner diameter of L.V Winding: outer diameter of L.V Winding: Length of mean turn is
din= dout= Lmt(h.v)=
250 326 904.7808
mm mm mm
H.V WINDING DESIGN: The H.V Winding design is done using the cross over winding using rectangular conductors. A total of 819 turns are accomodated using 13 coils and 7 coils per layer. Each coil consists of 9 horizontal winding turns.Thus total turns=7*13*9=819. voltage per coil is:
V/coil=
846.153846 V
the area of each conductor is 10.9mm^2 thus, modified value of current density:
d'=
2.78009452 A/mm^2
Dimensions for each conductor
h= w=
3.8 3
mm mm
including the 0.25mm insulation all over:
h'= w'=
4.3 3.5
mm mm
Thus,
hc= wc=
30.1 31.5
mm mm
Coil Height coil width ;
using inter coil spacing of 5.5mm and inter layer(horizontal)spacing of 1mm Winding Height=
H= W=
457.3 39.5
mm mm
Taking the clearance between H.V and L.V as: a=
12
mm
inner diameter of H.V Winding: outer diameter of H.V Winding:
din= dout=
350 429
mm mm
Length of mean turn is
Lmt(h.v)=
1223.6532
mm
OPERATING CHARACTERISTICS: RESISTANCE; Resistivity of copper is=
r=
0.021
W-mm^2/m
Resistance of:
H.V:
r(H.V)=
1.8026211
Resistance of:
L.V:
r(L.V)=
0.00070048 W
Req= Rp.u=
3.17782364 W 0.00875434
Average mean turn is: Average Height of Winding:
Lmt(avg) Lc=
1064.217 454.9
Ratio of Lmt/Lc is
Ratio=
2.33945263
value of reactance is:
X=
20.8789598 W
p.u value of reactance:
Xp.u=
0.0575178
Net impedance is:
Z=
20.9028936 W
p.u value of impedance is:
Z(p.u)=
0.05758373
Equivalent Resistance refered to H.V: p.u value of resitance=
W
REACTANCE: mm mm
REGULATION: at 0.8 pf full load regulation is:
Reg(p.u)= 0.04151415
at upf full load the regulation is:
Reg(p.u)= 0.00875434
LOSSES AND EFFICIENCY: IRON LOSSES: From the loss graph of the crgo grade 56 loss curves, Loss per unit volume is
Loss/vol=
1.42
W/kg
now total fluxpath length is: volume of the iron parts:
L= volume=
4120 mm 0.16632984 m^3
Taking density of grade 56 crgo is:
s=
7650
Total mass of the iron parts is:
M=
1272.42324 kgs
thus total iron loss is:
Pi=
1806.841
W
Total copper Losses is=
Pc=
8754.3351
W
kg/m^3
thus %full load at max efficiency is
x=
0.45430591
and efficiency at
0.8pf is:
h=
0.98697054
upf is:
h=
0.9895492
MAGNETIZATION CHARACTERISTICS: Total iron losses=
Pi=
1806.841
W
Thus the loss component of no load current is: Il=
0.05475276
now the mmf/meter for iron is:
Ati/m=
110
AT
Total mmf required is
Ati=
453.2
AT
taking atotal of 0.05mm air gap per joint Total airgap length is:
La/g=
0.3
mm
mmf required for the air gap is:
Ata/g=
381.063927 AT
Total mmf Required is
AT0=
834.263927 AT
the magnetizing current per phase is:
Im=
0.25438239
thus the no load current is:
I0=
0.26020812 0.858687 % of full load current.
OVERALL TANK DIMENSIONS AND VOLUME: Taking the basic clearances of:
b= l= h=
50 80 300
mm mm mm
Width of the tank is=
W= L= H=
1439 589 1290
mm mm mm
thus total volume of tank is:
V=
1.131
m^3
for calculation of copper volume: volume of lv winding: volume of hv winding:
V(lv)= V(hv)=
0.01555771 m^3 0.02210328 m^3
Thus total copper volume is total iron volume is
V= V=
0.11298295 m^3 0.16632984 m^3
thus volume of oil in transformer (including radiators is:)
V(oil)=
1.34667402 m^3
1450 600 1300
mm mm mm
CONSERVATOR DESIGN: Volume of conservator is taken . as 10% of oil in tank and radiators thus taking length to diameter ratio as:
V(cons)=
0.1346674
m^3
R= D= L=
2.5 0.40933341 m 1.02333352 m
DESIGN OF COOLING ARRANGEMENTS (RADIATORS): Value of thermal coefficient at 75 deg c is
C=
12.5
W/(m^2-degC)
Temperature rise limits specified:
q=
40
degC
Total Watts dissipating from surface for the requisite temperature rise is:
W/m^2=
500
W/m^2
Surface Area of Tank is:
St=
5.33
m^2
Total Watts that are dissipated from the tank walls naturaly is=
Diss=
2665
W
Thus the total watts required to be dissipated by radiators is
Rdwats=
7896.1761
W
Taking height of radiators as: thus the watts per section for this height and temperature is:
Hrad=
1200
mm
W/sectn=
167
thus no of section required is
sections=
47.2824916
now the values of spacing constants are:
c= b= d=
0.955 0.93 1
Modified value of no of sections required
sections=
53.2370564 56
Thus we select 56 elliptical Radiator sections in total of 6 Radiators,with 7 sections per radiator. Thus Radiator section dimensions are:
h= w= l=
Horizontal distance between each Section is: vertical surface area of each radiator is: Volume of each radiator= Net Volume of all Radiators
A= V= Vnet=
1200 300 25
mm mm mm
50
mm
0.00736588 m^2 0.00883905 m^3 0.4949868 m^3
TRANSFORMER DESIGN
KVA= 25000 Vp(line)= 33 Vs(line)= 6.9 frequency= 50 phase= 3 transportation height=3.5m load loss= 20 no load loss= 110 load loss capitalization= load loss capitalization= Bmax= 1.7 tesla current density= 3 width of conductor= 17y>7 specific loss= 1.2 copper rate= 425 iron rate= 180
