(27) size of transformer's circuit braker & fuse

8/22/2019 (27) Size of Transformer's Circuit Braker & Fuse

http://slidepdf.com/reader/full/27-size-of-transformers-circuit-braker-fuse 1/31

Enter Data in White Background Cells

Calculation Size of Circuit Breaker & Fuse are as per NEC 450.3

Sr.No Equipment Kw P.F Qty Equipment D.F Total Kva D.F (Kva)

3 1 1 100% 3 30 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 00 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 00 0

0 0

0 0

0 0

3

100%

3

Calculate Size of Transformer / Fuse / Circuit Breaker

Total D.F (Kva)

Total Load (Kva)

Total Load D.F

CONNECTED EQUIPMENT TO TRANSFORMER



Total D.F Load 3 Kva

Primary Side Voltage (L-L): 415 VoltSecondary Side Voltage (L-L): 230 Volt

Transformer Impedance: 5%

Transformer Connection Y-Y

Size of Transformer: 3 Kva OR Kva 3

Efficency of Transformer at Full Load 98.40% 0.984

Efficency of Transformer at 1/4 Load 97.50% 0.975

Location of Transformer

Provide Protection on Transformer:

Type Protection on Primary & Secondary Side:

Primary Line Voltage (L-L) 415 Volt

Primary Phase Voltage (L-P) 240 Volt

Primary Line Current(L-L): 4 Amp

Primary Phase Current(L-P): 4 Amp

Secondary Line Voltage (L-L) 230 Volt

Secondary Phase Voltage (L-P) 133 Volt

Secondary Phase Current(L-P): 7.5 Amp

Secondary Line Current(L-L): 7.5 Amp

Size of Circuit Breaker on Primary Side: 10 Amp

Size of Fuse on Primary Side: 10 Amp

Size of Circuit Breaker on Secondary Side: 10 AmpSize of Fuse on Secondary Side: 10 Amp

Total Losses@ Full Load 49 Watt

Total Losses@ 1/4 Load 19 Watt

Full Load Copper Loss 32 Watt

Core Loss 17 Watt

Pri.Side & Sec.Side

Size of Circuit Breaker / Fuse (As per NEC 450.3)

Transformer Losses

Transformer Voltage / Current

:Results:

Transformer Details

Jignesh.Parmar www.electricalnotes.wordpress.com,

[email protected]

Enter Detail of TC/CB/Fuse

Supervised Not Supervised

Circuit Breaker Fuse

http://www.electricalnotes.wordpress.com/






Standard Size of 3 Phase

Transformer (KVA)

Standard Size of Fuse / C.B

(Amp)1 1

3 36 6

9 10

15 15

25 20

30 25

37.5 30

45 35

50 40

75 45

112.5 50

150 60

225 70300 80

500 90

750 100

1000 110

1500 125

2000 150

2500 160

3750 175

5000 200

7500 225

10000 250

12000 300

15000 350

20000 400

25000 450

30000 500

37500 600

50000 700

60000 800

75000 1000

100000 1200

1600

2000

2500

30004000

5000

6000

Size of Transformer / Fuse / Circuit Breaker



HOME



1 1 1 1

3 6 3 36 10 6 6

10 15 10 10

15 20 15 15

20 25 20 20

25 30 25 25

30 35 30 30

35 40 35 35

40 45 40 40

45 50 45 45

50 60 50 50

60 70 60 60

70 80 70 7080 90 80 80

90 100 90 90

100 110 100 100

110 125 110 110

125 150 125 125

150 160 150 150

160 175 160 160

175 200 175 175

200 225 200 200

225 250 225 225

250 300 250 250

300 350 300 300

350 400 350 350

400 450 400 400

450 500 450 450

500 600 500 500

600 700 600 600

700 800 700 700

800 1000 800 800

1000 1200 1000 1000

1200 1600 1200 1200

1600 2000 1600 1600

2000 2500 2000 2000

2500 3000 2500 2500

3000 4000 3000 30004000 5000 4000 4000

5000 6000 5000 5000

6000 6000 6000 6000

SupervisedUnSupervised

Fuse / Inverse Time C.B as per NEC (Amp) Fuse / Inverse Time C.B as per NEC (Amp)



2

3 3

2 3 6

1

1 1 3 C.B Fuse

3 3 6 1 600% 300%6 6 9 2 600% 300%

9 9 15 600% 300%

15 15 25 25 13

25 25 30 25 10

30 30 37.5

37.5 37.5 45

45 45 50

50 50 75

75 75 112.5

112.5 112.5 150

150 150 225 C.B

225 225 300300 300 500 1% 600%

500 500 750 2% 600%

750 750 1000 3% 600%

1000 1000 1500 4% 600%

1500 1500 2000 5% 600%

2000 2000 2500 6% 600%

2500 2500 3750 7% 400%

3750 3750 5000 8% 400%

5000 5000 7500 9% 400%

7500 7500 10000 10% 400%

10000 10000 12000

12000 12000 15000

15000 15000 20000

20000 20000 25000 Prim. 5% 0

25000 25000 30000 Sec. 0

30000 30000 37500

37500 37500 50000

50000 50000 60000

60000 60000 75000

75000 75000 100000 Prim. 5% 0

100000 100000 100000 Sec. 0

Primary

>6

Pri

%Imp

More Than

3 Phase T.C (KVA)



C.B

1% 600%

2% 600%

3% 600%

4% 600%

5% 600%

6% 600%

7% 400%

8% 400%

9% 400%

10% 400%

Protection

Method More than

9A

Primary only

protection

125%(NH)

Primary and

secondary protection

250%

Primary Only

Amp Pri

1 300%

2 167%

3 167%

4 167%

5 167%

6 167%

7 167%8 167%

9 167%

10 125%

4.17 167%

7.53 6.97

6

Primary & Secondary pro

Maximum Rating of Over curren

Pri

Primary only protecti

%ImpPri>6

More Than



Amp Pri

1 250%

2 250%

3 250%

4 250%

5 250%

6 250%

7 250%

8 250%

9 250%

10 250%

4.17 250%

7.53 10.43

10

10



0

C.B Fuse

250% 250%125% 125%

250% 250%

19 19 C.B Fuse C.B Fuse

15 15 10 10 10 10

<600

Fuse C.B Fuse C.B/Fuse

300% 300% 250% 250%

300% 300% 250% 250%

300% 300% 250% 250%

300% 300% 250% 250%

300% 300% 250% 250%

300% 300% 250% 250%

300% 250% 225% 250%

300% 250% 225% 250%

300% 250% 225% 250%

300% 250% 225% 250%

C.B 600% Fuse 300%

C.B 250% Fuse 250%

C.B 600% Fuse 300%

C.B 125% Fuse 125%

Primary Secondary

Secondary

00 >600

ary secondary

00V Supervised



<600

Fuse C.B Fuse C.B/Fuse

300% 300% 250% 125%

300% 300% 250% 125%

300% 300% 250% 125%

300% 300% 250% 125%

300% 300% 250% 125%

300% 300% 250% 125%

300% 250% 225% 125%

300% 250% 225% 125%

300% 250% 225% 125%

300% 250% 225% 125%

2A to 9A Less than

2A

More than

9A

Less than

9A

167% 300% Not required Not required

250% 250% 125%(NH) 167%

Sec

0%

0%

0%

0%

0%

0%

0%0%

0%

0%

0% 0

N/A

N/A

tection

t Protection for Transformers Less than 600 Volts

mary Protection Secondary Protection

ion

ary secondary00 >600

00V Not Supervised



Sec

167%

167%

167%

167%

167%

167%

167%

167%

125%

125%

167% 0

12.58

10

10

(27) size of transformer's circuit braker & fuse

Documents