Bus Bar Working

8/12/2019 Bus Bar Working

1/7

Ampacities and Mechanical Properties ofRectangular Copper Bus Bars

The ampacity tables presented here are for rectangular bus bars of Copper No. 110whose surface condition is similar to that of busses at typical installations. Ampacities

were calculated using a nominal conductivity of 99% IACS and should also beapplicable to other coppers with the same electrical conductivity. Listed for 60 Hz attemperature rises of 30, 60, and 65 C ambient, they ere determined from accurateemissivity coefficients measured by calorimetriC techniques. The methods aredescribed in "Electrical Coils and Conductors", by H.B. Dwight (McGraw-HillPublishing Co., New York, 1945, Chapter 19).

Am p ac i t y Cal cu la t io n s- Accurate emissivity is essential because it isused to calculate the heat dissipated by radiation, a factor in the generalequation for ampacity:

where I is ampacity (amp), WR is heat dissipated by radiation (watts), WCis heat dissipated by natural convection (watts), and R is resistance (ohms)at operating temperature and 60 Hz.

Table 1. Ampacities of Copper No. 110 Bus Bars- Ampacities in this table are forbus bars having an emissivity of 0.4.

This was observed on samples exposed for 60 days in an industrial environment, and itis probably identical to that of bus bars in service.

Direct-current ampacities may differ from AC ampacities because of AC skin effect:

where I DC is DC ampacity at 60 Hz (amp), and S is the skin effect ratio at 60 Hz.

Table 2. Mechanical Properties of Copper No. 110 Bus Bars- This table listsproperties useful in calculating such characteristics as stiffness and deflection that areoften required by designers of bus bar systems.

Table 3. Quick Bus Bar Selector- Knowing the ampacity, designers and estimatorscan get the approximate bus bar size. Ampacity of the bus bar selected must then beverified by checking table 1.

Table 4. Effect of Emissivity and Number of Busses on Ampacity- Data here showhow higher emissivities improve ampacity. Multiple busses also affect ampacity in anonlinear relationship. Ampacity may be raised by increasing heat dissipation throughthe use of convection cooling or surface treatments. Surface treatments whichemissivity are available.


2/7

Table 1. Ampacities of Copper No. 110Bus Bars

Dimensions,

In.

Area

WeightPer

Foot,Lb

DCResistanceat 20 C,Microhms

Per Ft

30 C Rise 50 C Rise 65 C Rise

SquareIn.

CircularMils,

Thousands

SkinEffectRatio

at70 C

60-HzAmpacity,*

Amp

SkinEffectRatio

at90 C

60-HzAmpacity,*

Amp

SkinEffect

Ratioat

105C

60-HzAmpacity,*

Amp

1/16 x 1/21/16 x 3/41/16 x 1

1/16 x 1 1/21/16 x 2

0.03120.04690.0625

0.09380.125

39.759.779.6

119159

0.1210.1810.241

0.3620.483

264.0175.0132.0

87.765.8

1.001.001.00

1.001.01

103145187

270345

1.001.001.00

1.001.01

136193250

355460

1.001.001.00

1.001.01

157225285

410530

1/8 x 1/21/8 x 3/41/8 x 1

1/8 x 1 1/21/8 x 21/8 x 2 1/2

1/8 x 31/8 x 3 1/21/8 x 4

0.06250.09380.125

0.1880.2500.312

0.3750.4380.500

79.6119159

239318397

477558636

0.2410.3620.483

0.7260.9661.21

1.451.691.93

132.087.765.8

43.832.926.4

21.918.816.5

1.001.001.01

1.011.021.02

1.031.041.04

153215270

385495600

710810910

1.001.001.01

1.011.021.02

1.031.031.04

205285360

510660800

9401,1001,200

1.001.001.01

1.011.021.02

1.031.031.04

235325415

590760920

1,1001,2501,400

3/16 x 1/23/16 x 3/4

3/16 x 13/16 x 1 1/23/16 x 2

3/16 x 2 1/23/16 x 33/16 x 3 1/2

3/16 x 4

0.09380.141

0.1880.2810.375

0.4690.5620.656

0.750

119179

239358477

597715835

955

0.3620.545

0.7261.091.45

1.812.172.53

2.90

87.758.4

43.829.321.9

17.514.612.5

11.0

1.001.01

1.011.021.03

1.041.051.07

1.09

195270

340480610

740870990

1,100

1.001.01

1.011.021.03

1.041.051.06

1.08

260360

455630810

9801,1501,300

1,450

1.001.01

1.011.021.03

1.031.041.06

1.07

300415

520730940

1,1501,3501,500

1,700

1/4 x 1/2

1/4 x 3/41/4 x 1

1/4 x 1 1/21/4 x 21/4 x 2 1/21/4 x 31/4 x 3 1/2

1/4 x 41/4 x 51/4 x 6

1/4 x 81/4 x 101/4 x 12

0.125

0.1880.250

0.3750.5000.6250.7500.875

1.001.251.50

2.002.503.00

159

239318

477637796955

1,110

1,2701,5901,910

2,5503,1803,820

0.483

0.7260.966

1.451.932.412.903.38

3.864.835.80

7.739.66

11.6

65.8

43.832.9

21.916.513.211.0

9.40

8.236.585.49

4.113.292.74

1.01

1.011.02

1.031.041.061.081.10

1.121.161.18

1.231.271.31

240

320400

560710850990

1,150

1,2501,5001,750

2,2502,7003,150

1.01

1.011.02

1.031.041.061.081.09

1.111.151.17

1.221.261.30

315

425530

740940

1,1501,3001,500

1,7002,0002,350

3,0003,6004,200

1.01

1.011.02

1.031.041.061.071.09

1.101.141.17

1.211.251.28

360

490620

8601,1001,3001,5501,750

1,9502,3502,700

3,4504,2004,900

3/8 x 3/43/8 x 1

3/8 x 1 1/23/8 x 23/8 x 2 1/2

3/8 x 33/8 x 3 1/23/8 x 4

3/8 x 53/8 x 63/8 x 8

3/8 x 103/8 x 12

0.2810.375

0.5620.7500.938

1.121.311.50

1.882.253.00

3.754.50

358477

715955

1,190

1,4301,6701,910

2,3902,8603,820

4,7705,730

1.091.45

2.172.903.62

4.355.065.80

7.268.69

11.6

14.517.4

29.321.9

14.611.0

8.77

7.356.285.49

4.383.662.74

2.191.83

1.021.03

1.051.081.12

1.151.181.20

1.241.271.33

1.381.42

415510

710880

1,050

1,2001,3501,500

1,8002,1002,650

3,2003,700

1.021.03

1.041.081.10

1.141.161.19

1.231.261.31

1.361.40

550680

9401,1501,400

1,6001,8002,000

2,4002,8003,550

4,3005,000

1.021.03

1.041.071.09

1.131.151.18

1.221.241.30

1.351.38

630790

1,1001,3501,600

1,8502,1002,350

2,8003,2504,100

4,9005,800

1/2 x 11/2 x 1 1/21/2 x 2

1/2 x 2 1/21/2 x 31/2 x 3 1/2

1/2 x 41/2 x 5

1/2 x 61/2 x 8

1/2 x 101/2 x 12

0.5000.7501.00

1.251.501.75

2.002.50

3.004.00

5.006 00

637955

1,270

1,5901,9102,230

2,5503,180

3,8205,090

6,3607 640

1.932.903.86

4.835.806.76

7.739.66

11.615.5

19.323 2

16.511.0

8.23

6.585.494.70

4.113.29

2.742.06

1.651 37

1.041.081.12

1.161.201.24

1.261.32

1.361.42

1.471 52

620830

1,000

1,2001,4001,550

1,7002,050

2,4003,000

3,6004 200

1.041.081.11

1.151.191.22

1.251.30

1.341.40

1.451 51

8201,1001,350

1,6001,8502,100

2,3002,750

3,1504,000

4,8005 600

1.041.071.10

1.141.181.21

1.241.29

1.331.39

1.441 50

9401,2501,550

1,8502,1502,400

2,6503,150

3,6504,600

5,5006 400


3/7

Table 2. Mechanical Properties of CopperNo. 110 Bus Bars

Dimensions,In.

Area

WeightPer

Foot,

Lb

Horizontal Axis Vertical Axis

YieldLoad,*

Lb

Square

In.

Circular

Mils,Thous.

Momentof

InertiaIn.4

SectionModulus,

In.3

Radiusof

GyrationIn.

Momentof

InertiaIn.4

SectionModulus,

In.3

Radiusof

GyrationIn.

1/16 x 1/21/16 x 3/4

1/16 x 11/16 x 1 1/21/16 x 2

0.03120.0469

0.06250.09380.125

39.759.7

79.6119159

0.121 0.181

0.241 0.362 0.483

0.000651 0.00220

0.00521 0.0176 0.0417

0.000260 0.00586

0.0104 0.0234 0.0417

0.1440.217

0.2890.4330.577

0.00001020.0000153

0.00002030.00003050.0000407

0.0003260.000488

0.0006510.0009770.00130

0.01800.0180

0.01800.01800.0180

7801,170

1,5602,3403,120

1/8 x 1/21/8 x 3/41/8 x 1

1/8 x 1 1/21/8 x 21/8 x 2 1/2

1/8 x 31/8 x 3 1/21/8 x 4

0.06250.09380.125

0.1880.2500.312

0.3750.4380.500

79.6119159

239318397

477558636

0.241 0.362 0.483

0.726 0.966 1.21

1.45 1.69 1.93

0.00130 0.00440 0.0104

0.0352 0.0833 0.163

0.281 0.447 0.667

0.00521 0.0117 0.0208

0.0469 0.0833 0.130

0.188 0.255 0.333

0.1440.2170.289

0.4330.5770.722

0.8661.011.16

0.00008140.0001220.000163

0.0002440.0003260.000407

0.0004880.0005700.000651

0.001300.001950.00260

0.003910.005210.00651

0.007810.009120.0104

0.03610.03610.0361

0.03610.03610.0361

0.03610.03610.0361

1,5602,3403,120

4,6906,2507,810

9,38010,94012,500

3/16 x 1/23/16 x 3/4

3/16 x 13/16 x 1 1/23/16 x 2

3/16 x 2 1/23/16 x 33/16 x 3 1/2

3/16 x 4

0.09380.141

0.1880.2810.375

0.4690.5620.656

0.750

119179

239358477

597715835

955

0.362 0.545

0.726 1.09 1.45

1.81 2.17 2.53

2.90

0.00195 0.00659

0.0156 0.0527 0.125

0.244 0.422 0.670

1.00

0.00781 0.0176

0.0312 0.0703 0.125

0.195 0.281 0.383

0.500

0.1440.217

0.2890.4330.577

0.7220.8661.01

1.16

0.0002750.000412

0.0005490.0008240.00110

0.001370.001650.00192

0.00220

0.002930.00440

0.005860.008790.0117

0.01460.01760.0205

0.0234

0.05410.0541

0.05410.05410.0541

0.05410.05410.0541

0.0541

2,3403,520

4,6907,0319,380

11,70014,10016,400

18,800

1/4 x 1/2

1/4 x 3/41/4 x 11/4 x 1 1/2

1/4 x 21/4 x 2 1/21/4 x 3

1/4 x 3 1/21/4 x 41/4 x 5

1/4 x 61/4 x 81/4 x 101/4 x 12

0.125

0.1880.2500.375

0.5000.6250.750

0.8751.001.25

1.502.002.503.00

159

239318477

637796955

1,1101,2701,590

1,9102,5503,1803,820

0.483

0.726 0.966 1.45

1.93 2.41 2.90

3.38 3.86 4.83

5.80 7.73 9.6611.6

0.00260

0.00879 0.0208 0.0703

0.167 0.326 0.562

0.893 1.33 2.60

4.5010.720.836.0

0.0104

0.0234 0.0417 0.0938

0.167 0.260 0.375

0.510 1.667 1.04

1.50 2.67 4.17 6.00

0.144

0.2170.2890.433

0.5770.7220.866

1.011.161.44

1.732.312.893.46

0.000651

0.0009770.001300.00195

0.002600.003260.00391

0.004560.005210.00651

0.007810.001040.01300.0156

0.00521

0.007810.01040.0156

0.02080.02600.0312

0.03650.04170.0521

0.06250.08330.1040.125

0.0722

0.07220.07220.0722

0.07220.07220.0722

0.07220.07220.0722

0.07220.07220.07220.0722

3,120

4,6906,2509,380

12,50015,60018,800

21,90025,00031,200

37,50050,00062,50075,000

3/8 x 3/43/8 x 1

3/8 x 1 1/23/8 x 23/8 x 2 1/2

3/8 x 33/8 x 3 1/23/8 x 4

3/8 x 53/8 x 63/8 x 8

3/8 x 103/8 x 12

0.2810.375

0.5620.7500.938

1.121.311.50

1.882.253.00

3.754.50

358477

715955

1,190

1,4301,6701,910

2,3902,8603,820

4,7705,730

1.09 1.45

2.17 2.90 3.62

4.35 5.06 5.80

7.26 8.6911.6

14.517.4

0.0132 0.0312

0.105 0.250 0.488

0.844 1.34 2.00

3.91 6.7516.0

31.254.0

0.0352 0.0625

0.141 0.250 0.391

0.562 0.766 1.00

1.56 2.25 4.00

6.25 9.00

0.2170.289

0.4330.5770.722

0.8661.011.16

1.441.732.31

2.893.46

0.003300.00439

0.006590.008790.0110

0.01320.01540.0176

0.02200.02640.0352

0.04390.0527

0.01760.0234

0.03520.04690.0586

0.07030.08200.0938

0.1170.1410.188

0.2340.281

0.1080.108

0.1080.1080.108

0.1080.1080.108

0.1080.1080.108

0.1080.108

7,0309,380

14,10018,80023,400

28,10032,80037,500

46,90056,20075,000

93,800112,000

1/2 x 11/2 x 1 1/21/2 x 2

1/2 x 2 1/21/2 x 31/2 x 3 1/2

1/2 x 41/2 x 51/2 x 6

1/2 x 81/2 x 101/2 x 12

0.5000.7501.00

1.251.501.75

2.002.503.00

4.005.006.00

637955

1,270

1,5901,9102,230

2,5503,1803,820

5,0906,3607,640

1.93 2.90 3.86

4.83 5.80 6.76

7.73 9.6611.6

15.519.323.2

0.0417 0.0141 0.0333

0.0651 1.12 1.79

2.67 5.21 9.00

21.3 41.7 72.0

0.0833 0.188 0.333

0.521 0.750 1.02

1.33 2.08 3.00

5.33 8.3312.0

0.2890.4330.577

0.7220.8661.01

1.161.441.73

2.312.893.46

0.01040.01560.0208

0.02600.03120.0365

0.04170.05210.0625

0.08330.1040.125

0.04170.06250.0833

0.1040.1250.146

0.1670.2080.250

0.3330.4170.500

0.1440.1440.144

0.1440.1440.144

0.1440.1440.144

0.1440.1440.144

9,00013,50018,000

22,50027,00031,500

36,00045,00054,000

72,00090,000

108,000


4/7

Table 3. Quick Bus Bar Size Selector

RequiredAmpacity,*

(Range)Amp

Bus Bar Dimentions, In.**


100 (100-149) 1/16x1/2,1/16x3/4 1/16x1/2

150 (150-199)

1/16x11/8x1/2

3/16x1/2

1/16x3/4

1/16x1/2

200 (200-249) 1/8x3/4

1/4x1/2

1/8x1/2

1/16x3/41/8x1/2

250 (250-299)

1/16x1 1/21/8x13/16x3/4

1/16x11/8x3/43/16x1/2

1/16x1

300 (300-349)

1/16x2

3/16x1

1/4x3/4

1/4x1/2

1/8x3/43/16x1/2

350 (350-399) 1/8x1 1/2

1/16x1 1/21/8x13/16x3/4 1/4x1/2

400 (400-449)

1/4x3/43/8x3/4

1/4x3/4 1/4x1/2

400 (400-449)

1/4x13/8x3/4

1/4x3/4

1/16x1 1/21/8x13/16x3/4

450 (450-499)

1/8x23/16x1/2

1/16x2

3/16x1 1/4x3/4

500 (500-599)

1/4x1 1/23/8x1

1/8x1 1/2

1/4x13/8x3/4

1/16x21/8x1 1/23/16x1


5/7

600 (600-699)

1/8x2 1/23/16x2

1/2x1

1/2x1

1/8x23/16x1 1/2

1/4x1

1/4x1

3/8x3/4

700 (700-799) 1/8x33/16x2 1/21/4x23/8x1 1/2

1/4x1 1/2

1/8x23/16x1 1/23/8x1

800 (800-899)

1/8x3 1/2

3/16x31/4x2 1/23/8x2

1/8x2 1/2

3/16x2

1/2x1

1/4x1 1/2

900 (900-999)

1/8x43/16x3 1/2

1/4x3

1/8x33/16x2 1/2

1/4x2

3/8x1 1/2

1/8x2 1/2

1/2x1

1000 (1000-1249)

3/16x41/4x3 1/2

3/8x2 1/2, 3/8x31/2x2, 1/2x2 1/2

1/8x4

3/16x31/4x2 1/2

3/8x2

1/8x3

3/16x2 1/21/4x2

3/8x1 1/2

1250 (1250-1499)

1/4x4

3/8x3 1/21/2x3

3/16x3 1/2,

3/16x41/4x3

3/8x2 1/2

1/2x2

1/8x4

3/16x31/4x2 1/2

3/8x2

1500 (1500-1749) 1/4x5

3/8x4

1/2x3 1/2, 1/2x4

1/4x3 1/2,

1/4x43/8x3

1/2x2 1/2

3/16x3 1/2,3/16x4

1/4x33/8x2 1/2

1/2x2

1750 (1750-1999)

1/4x63/8x5

3/8x3 1/21/2x3

1/4x3 1/2,1/4x43/8x31/2x2 1/2

2000 (2000-2499)

1/4x8

3/8x61/2x5, 1/2x63/4x4, 3/4x5

1/4x6

3/8x51/2x4

1/4x5

3/8x41/2x3 1/2

2500 (2500-2999)

1/4x103/8x8

3/4x6

3/8x61/2x5

3/4x4

1/4x63/8x51/2x4

3000 (3000-3499)

1/4x123/8x10

1/2x8

1/4x8

1/2x63/4x5

1/4x83/8x6

1/2x53/4x4

RequiredAmpacity,*

(Range)Amp

Bus Bar Dimentions, In.**



6/7


7/7

Table 4. Effect of Emissivity and Number ofBusses on Ampacity

Numberof

1/4x4

in.Busses*

Ampacity, Amp


Emissivity Emissivity Emissivity

0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9

1 1100 1250 1400 1600 1500 1700 1900 2000 1700 1950 2200 2300

2 1900 2050 2200 2300 2550 2750 2950 3100 2950 3200 3400 3600

3 2500 2700 2850 3000 3400 3600 3850 4000 3950 4200 4500 4600

4 3100 3300 3450 3600 4200 4400 4700 4800 4900 5100 5400 5600

* 1/4 in. spacing. Ampacities of bus bar systems of other configurations must becalculated, taking into account size, spacing, number of bus bars and overallskin-effect ratio.

Documents

Bus Bar Working