Enter Data in White Background Cells
Calculate Size of Transformer / Fuse / Circuit Breaker
Calculation Size of Circuit Breaker & Fuse are as per NEC 450.3
CONNECTED EQUIPMENT TO TRANSFORMER
Sr.No
Equipment
Kw
P.F
Qty
12
Equipment
D.F
100%
Total Load (Kva)
Total Load D.F
Total D.F (Kva)
Total
Kva
12
0
0
0
0
0
0
0
D.F (Kva)
12
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
12
100%
12
Jignesh.Parmar
www.electricalnotes.wordpress.com,
jiguparmar@yahoo.com
Enter Detail of
TC/CB/Fuse
Transformer Details
Total D.F Load
12
Kva
Primary Side Voltage (L-L):
Secondary Side Voltage (L-L):
Transformer Impedance:
Transformer Connection
Size of Transformer:
Efficency of Transformer at Full Load
Efficency of Transformer at 1/4 Load
Location of Transformer
440
220
5%
-
15
98.40%
97.50%
Volt
Volt
Provide Protection on Transformer:
Pri.Side & Sec.Side
Kva OR
0.984
0.975
Supervised
Circuit Breaker
Type Protection on Primary & Secondary Side:
:Results:
Transformer Voltage / Current
Primary Line Voltage (L-L)
Primary Phase Voltage (L-P)
Primary Line Current(L-L):
Primary Phase Current(L-P):
Secondary Line Voltage (L-L)
Secondary Phase Voltage (L-P)
Secondary Phase Current(L-P):
Secondary Line Current(L-L):
440
440
20
11
220
220
39.4
22.7
Volt
Volt
Amp
Amp
Volt
Volt
Amp
Amp
Size of Circuit Breaker / Fuse (As per NEC 450.3)
Size of Circuit Breaker on Primary Side:
Size of Fuse on Primary Side:
Size of Circuit Breaker on Secondary Side:
Size of Fuse on Secondary Side:
45
45
25
25
Amp
Amp
Amp
Amp
244
96
158
86
Watt
Watt
Watt
Watt
Transformer Losses
Total Losses@ Full Load
Total Losses@ 1/4 Load
Full Load Copper Loss
Core Loss
Kva
Not Supervised
Fuse
15
Size of Transformer / Fuse / Circuit Breaker
Standard Size of 3 Phase
Transformer (KVA)
1
3
6
9
15
25
30
37.5
45
50
75
112.5
150
225
300
500
750
1000
1500
2000
2500
3750
5000
7500
10000
12000
15000
20000
25000
30000
37500
50000
60000
75000
100000
Standard Size of Fuse / C.B
(Amp)
1
3
6
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
125
150
160
175
200
225
250
300
350
400
450
500
600
700
800
1000
1200
1600
2000
2500
3000
4000
5000
6000
HOME
UnSupervised
Supervised
Fuse / Inverse Time C.B as per NEC (Amp)
Fuse / Inverse Time C.B as per NEC (Amp)
1
3
6
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
125
150
160
175
200
225
250
300
350
400
450
500
600
700
800
1000
1200
1600
2000
2500
3000
4000
5000
6000
1
6
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
125
150
160
175
200
225
250
300
350
400
450
500
600
700
800
1000
1200
1600
2000
2500
3000
4000
5000
6000
6000
1
3
6
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
125
150
160
175
200
225
250
300
350
400
450
500
600
700
800
1000
1200
1600
2000
2500
3000
4000
5000
6000
1
3
6
10
15
20
25
30
35
40
45
50
60
70
80
90
100
110
125
150
160
175
200
225
250
300
350
400
450
500
600
700
800
1000
1200
1600
2000
2500
3000
4000
5000
6000
12
#N/A
0
15
9
15
3 Phase T.C (KVA)
1
3
6
9
15
25
30
37.5
45
50
75
112.5
150
225
300
500
750
1000
1500
2000
2500
3750
5000
7500
10000
12000
15000
20000
25000
30000
37500
50000
60000
75000
100000
1
3
6
9
15
25
30
37.5
45
50
75
112.5
150
225
300
500
750
1000
1500
2000
2500
3750
5000
7500
10000
12000
15000
20000
25000
30000
37500
50000
60000
75000
100000
Primary
2
3
6
9
15
25
30
37.5
45
50
75
112.5
150
225
300
500
750
1000
1500
2000
2500
3750
5000
7500
10000
12000
15000
20000
25000
30000
37500
50000
60000
75000
100000
100000
1
2
C.B
600%
600%
600%
118
125
%Imp
Fuse
300%
300%
300%
59
60
More Than 600V
Primary
>600
C.B
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%
600%
600%
600%
600%
600%
600%
400%
400%
400%
400%
Prim.
Sec.
5%
0
0
Prim.
Sec.
5%
0
0
%Imp
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%
More Than 600V
Primary
>600
C.B
600%
600%
600%
600%
600%
600%
400%
400%
400%
400%
Maximum Rating of Over current Protection fo
Protection
Method
Primary only
protection
Primary and
secondary protection
Primary Only
19.68
22.73
Primary Protectio
More than
9A
125%(NH)
250%
Primary only protection
Amp
Pri
1
300%
2
167%
3
167%
4
167%
5
167%
6
167%
7
167%
8
167%
9
167%
10
125%
125%
24.60
20
Primary & Secondary protection
Amp
1
2
3
4
5
6
7
8
9
10
19.68
22.73
Pri
250%
250%
250%
250%
250%
250%
250%
250%
250%
250%
250%
49.21
45
45
Secondary
C.B
250%
125%
125%
49
50
More Than 600V
Primary
>600
Fuse
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
Fuse
250%
125%
125%
49
50
C.B
300%
300%
300%
300%
300%
300%
250%
250%
250%
250%
C.B
45
Primary
Fuse
45
Supervised
secondary
>600
<600
Fuse
C.B/Fuse
250%
250%
250%
250%
250%
250%
225%
225%
225%
225%
250%
250%
250%
250%
250%
250%
250%
250%
250%
250%
C.B
C.B
600%
250%
Fuse
Fuse
300%
250%
C.B
C.B
600%
125%
Fuse
Fuse
300%
125%
Secondary
C.B
Fuse
25
25
More Than 600V
Primary
>600
Fuse
Not Supervised
secondary
>600
<600
Fuse
C.B/Fuse
C.B
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
300%
250%
250%
250%
250%
250%
250%
250%
250%
250%
250%
225%
225%
225%
225%
125%
125%
125%
125%
125%
125%
125%
125%
125%
125%
of Over current Protection for Transformers Less than 600 Volts
Primary Protection
Secondary Protection
2A to 9A
More than
Less than
9A
9A
Not required Not required
167%
Less than
2A
300%
250%
250%
nly protection
Sec
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
N/A
N/A
condary protection
125%(NH)
167%
Sec
167%
167%
167%
167%
167%
167%
167%
167%
125%
125%
125%
28.41
25
25
