Electrical Engineering is a free introductory textbook to the basics of electrical engineering. See the editorial for more information....



Appendix

Author: E.E. Kimberly

TABLE A - ALLOWABLE CURRENT- CARRYING CAPACITIES OF CONDUCTORS IN AMPERES Not More Than Three Conductors in Raceway or Cable

(Based on Room Temperature of 30 C. 86 F.)

Size AWG MCM

Rubber TypeR Type RW TypeRU

(14-6)

Rubber Type RH

Paper

Asbestos Var-Cam Type AVA Type AVL

Impregnated Asbestos Type AI (14-8) Type AIA

Asbestos Type A (14-8) Type AA

Thermoplastic Asbestos Type TA

Thermoplastic TypeT (14-4/0) TypeTW (14^/0)

Var-Cam TypeV

Asbestos Var-Cam Type AVB

14 12 10

8

15 20 30 40

15 20 30 45

25 30 40 50

30 35

45 60

30 40 50 65

30 40 55

70

6 4 3 2 1

55

70 80 95 110

65 85 100 115 130

70 90 105 120 140

80 105 120 135 160

85 115 130 145 170

95 120 145 165 190

0

00 000 0000

125 145 165 195

150 175 200 230

}55 185 210 235

190 215 245 275

200 230 265 310

225 250

285 340

250 300 350 400 500

215 240 260 280 320

255 285 310 335 380

270 300 325 360 405

315 345 390 420 470

335 380 420 450 500

...

600 700 750 800 900

355

385 400 410 435

420 460 475 490 520

455 490 500 515 555

525 560 580 600

545 600 620 640

 

1,000 1,250 1,500 1,750 2,000

455 495 520 545 560

545 590 625 650 665

585 645 700 735

775

680 785 840

730

...

CORRECTION FACTOR FOR ROOM TEMPERATURES OVER 30 C. 86 F.

C F

40 104 45 113 50 122 55 131

.82 .71 .58 .41

.88 .82 .75 .67

.90

.85 .80

.74

.94 .90

.87 .83

.95 , .92 .89 .86

...

60 140 70 158 75 167 80 176

...

.58 .35

.67 .52 .43 .30

.79 .71 .66 .61

.83 .76 .72 .69

.91

.87 .86 .84

90 194 100 212

120 248 140 284

...

...

...

.50

.61 .51

.80 .77 .69 .59

TABLE B - ALLOWABLE CURRENT-CARRYING CAPACITIES OF CONDUCTORS IN AMPERES Single Conductor in Free Air

(Based on Room Temperature of 30 C. 86 F.)

Size AWG MCM

Rubber Type R TypeRW Type RU (14-6)

Rubber TypeRH

Thermoplastic Asbestos Type TA

Asbestos Var-Cam Type AVA Type AVL

Impregnated Asbestos

typeAI

(14-8)

Type AIA

Asbestos

Type A

(14-8)

Type AA

Slow-Burning Type SB

Var-Cam Type V

Weatherproof TypeWP Type SBW

Thermoplastic TypeT Type TW

Asbestos Var-Cam Type AVB

14 12

10 8

20 25 40 55

20 25 40

65

30

40 55 70

40 50 65

85

40 50 70 90

45 55 75 100

30 40 55 70

6

4 3 2

1

80 105 120 140 165

95 125 145 170 195

100 135 155 180 210

120 160 180 210 245

125 170 195 225 265

135 180 210 240 280

100 130 150 175 205

0 00 000 0000

195 225 260 300

230

265 310 360

245 285 330 385

285

330 385 445

305 355 410 475

325 370 430 510

235 275 320 370

250 300 350 400 500

340 375* 420 455 515

405 445 505 545 620

425 480 530 575 660

495 555 610 665 765

530 590 655 710 815

 

410 460 510 555 630

600 700 750 800 900

575 630 655 680 730

690 755 785 815 870

740 815 845 880 940

855 940 980 1020

910 1005 1045 1085

 

710 780 810 845 905

1,000 1,250 1,500 1,750 2,000

780 890 980 1070 1155

935 1065 1175 1280 1385

1000 1130 1260 1370 1470

1165

1240

...

965

1215

1405

1450

   

ins

....

 

CORRECTION FACTOR FOR ROOM TEMPERATURES OVER 30 C. 86 F.

C F 40 104 45 113 50 122 55 131

.82 .71 .58 .41

.88 .82 .75 ,67

.90 .85

.80 .74

.94 .90

.87 .83

.95 .92 .89 .86

...

....

60 140 70 158 75 167 80 176

 

.58 .35

.67 .52 .43 .30

.79 .71 .66 .61

.83 .76 -.72 .69

.91

.87 .86 .84

 

90 194 100 212 120 248 140 284

     

.50

.61 .51

.80 .77 .69 .59

 
     
       
         

FULL LOAD CURRENTS OF MOTORS

The following data are approximate full-load currents for motors of various types, frequencies, and speeds. They have been compiled from average values for representative motors of their respective classes. Variations of 10 per cent above or below the values given may be expected.

Hp

of

Motor

Amperes - Full-load Current

Direct-current Motors

Alternating-current Motors

Single-phase Motors

Squirrel-cage Induction Motors

Slip- ring Induction Motors

Two-phase

Three-phase

Two-phase

Three-phase

115-

volt

230-

volt

550-

volt

110-

volt

220-

volt

110-

volt

220-

volt

44O-

volt

550-

volt

2200-

volt

110-

volt

220-

volt

440-

volt

550-

volt

2200-

volt

110-

volt

220-

volt

440-

volt

550-

volt

2200-

volt

110-

volt

220-

volt

440-

volt

550-

volt

2200-

volt

?

     

7.6

1 R

                                       

4.5 6.5

2.3 3.3

"Y.4

8.0 9.6

4.0

4.8

4.1

4.8

2.1 2.4

1.6

1.2

0.9 1.0

 

5.0

5.4

2.5 2.8

1.3

1.4

i.o 1.1

                     

.....

6.2

3.1

1.6

1.3

 

7.2

3.6

1.8

1.5

 
 

1

1 1/2

2

8.4 12.5 16.1

4.2 6.3

8.3

1.7 2.6 3.4

11.0 15.0 20.0

5.5 7.5 10.0

5.6

7.8 9.7

2.8 3.9 4.9

1.4 2.0 2.4

1.1 1.7 2.0

 

6.6 9.4 12.0

3.3 4.7 6

1.7 2.4 3.0

1.3 2.0 2.4

"

6.7 11.7 12.5

3.4 5.9 6.3

1.7 3.0 3.1

1.4 2.3 2.5

.....

7.8

3.9

2.0

1.6

 
 
 

14.4

7.2

3.6

2.9

 
   

3 5 7*

23 40

58

12.3 19.8 28.6

5.0

8.2 12

27.8 46.6 67.6

13.9 23.3 33.8

 

7.8 13 19

3.9 6.5 9.5

3.1

5.2 7.6

   

9 15

22

4.5 7.5 11

4.0 6.0 9.0

   

8.7 13.0 20.0

4.3 6.5 10.0

3.5 5.2 7.6

 

20.2

10 15

25

5.0 7.5 13

4 6 10

 
       
   

.....

     

10 15 20

75 112 149

38 56 74

16 23

31

86.0

43.0

....

24 33

45

11.3 16.5 22.5

9.4 13,2

18.2

   

27 38 52

14 19 26

11 15 21

   

24.3 39 49

12.1 19.5 24.7

10.0 15.6 19.8

   

28 45 56

14 23

28

11 18 22

 
   
     

5.0

 

5.7

     
         

25 30 40

185 220 294

92 110 146

38 45 61

     

56

67 88

27.7 33.5

44

22.2 27.0 35.5

6.4 7.4 9.5

 

64 77 101

32 39 51

26

31 40

7 8 10

 

60 72 93

30.0 36.0 46.5

24.0 28.8 37.3

6.4 7.8 9.5

 

67 82 106

34 41 53

27 33 42

7.5 9 11

       
     

50 60

75

364 436 540

180 215 268

75 90 111

     

109

129 156

54 65 78

43.5 52.0 62.5

12.1 13.5 16.7

 

125 149 180

63 75 90

50 60

72

13 15 19

 

113 135 164

57 68 82

45

54 65

12.1 14.0

17.3

 

128 150

188

64 75 94

51 60

75

14

16 19

     
     

.....

100 125 150

;;::;

357 440

146 184 ??0

     

213 270

107 134 156

87 109

125

21.7 27.0 31.2

.....

246 310 360

123 155 180

98 124 144

25 32 36

....

214

267 315

108 134 158

87 108

127

21.7

27 32

 

246 310 364

123

155 182

99 124 145

25 31 37

     
     

175 200

                                               
             

217

173

43.3

 

480

240

195

49

 

430

216

173

44

 

490

245

196

5*2

     

Maximum Allowable Rating of Branch Circuit Fuses

         

With Code

 
         

Letters

 
       

With Code Letters

Squirrel cage

 
       

Single-phase and squirrel

and synchro-

 
 

Minimum size conductor

For Running Protection of Motors

With Code Letters

Single-phase and squirrel

cage and synchronous. Full voltage, resistor or reactor starting, Code letters B to E inc.

nous Auto-transformer starting, Code letters B to E

With Code Letters

All motors

Full load current rating of motor amperes

in raceways For conductors in air or for other insulations see Tables A and B

 

cage and synchronous. Full voltage, resistor and reactor

Auto-transformer starting, Code letters F to R inc. Without Code Letters

inc. Without Code Letters

Squirrel cage

Code letter A. Without Code Letters

 

AWG AND MCM

Maxi-

Maximum

starting, Code letters F to R

Squirrel cage and synchronous, auto-trans-

and synchronous, auto-transformer

DC and wound-rotor

   

mum

setting

inc.

former starting, High

starting, High

motors.

   

rating

oft

Without Code

reactance squirrel

reactance

 
   

of

time-limit

Letters

cage.***

squirrel

 
       

N.E.C.

protective

same as above.

Both not more than

cage.***

 
 

Type R

TYPE

RP

Type

Rh

fuses

device

 

30 amperes

Both more than 30

 
       

Amperes

Amperes

   

amperes.

 

Col. No. 1

2

3

4

5

6

7

8

9

10

1**

14

14

14

2*

1.25*

15

15

15

15

2**

14

14

14

3*

2.50*

15

15

15

15

3**

14

14

14

4*

3.75*

15

15

15

15

4**

14

14

14

6*

5.0 *

15

15

15

15

5**

14

14

14

8*

6.25*

15

15

15

15

6**

14

14

14

8*

7.50*

20

15

15

15

7

14

14

14

10*

8.75*

25

20

15

15

8

14

14

14

10*

10.0 *

25

20

20

15

9

14

14

14

12*

11.25*

30

25

20

15

10

14

14

14

15*

12.50*

30

25

20

15

11

14

14

14

15*

13.75*

35

30

25

20

12

14

14

14

15

15.00

40

30

25

20

13

12

14

14

20

16.25

40

35

30

20

14

12

14

14

20

17.50

45

35

30

25

15

12

12

14

20

18.75

45

40

30

25

16

12

12

14

20

20.00

50

40

35

25

17 18 19 20

10 10 10 10

12 12 10 10

14 12 12 12

25 25 25 25

21.25 22.50 23.75 25.0

60 60 60 60

45 45 50 50

35 40 40 40

30 30 30 30

22 24 26 28

8 8 8 8

10 10 8

8

10 10 10 10

30 30 35 35

27.50 30.00 32,50 35.00

70 80 80 90

60 60 70 70

45 50 60 60

35 40 40 45

30

32 34 36

6 6 6 6

8 8 6 6

8 8 8 8

40 40

45 45

37.50 40.00 42,50 45.00

90 100 110 110

70 80 90 90

60 70 70 80

45 50 60 60

38 40 42

44

5 5 5 4

6 6 6

5

8 6 6 6

50 50 50 60

47.50 50.00 52.50 55.0

125 125 125 125

100 100 110 110

80 80 90 90

60 60 70 70

46

48 50

52 54

4

4 3 3 3

5 5 5 4 4

6 6 6 6

5

60 60 60 70 ' 70

57.50 60.0 62,50 65.0 67.50

150 150 150

175 175

125 125 125 150 150

100 100 100 110

110

70 80 80 80 90

56 58 60 62

2 2 2 2

4 3 3 3

5 5 5 4

70 70 80 80

70.00 72.50 75.00 77.50

175 175 200 200

150 150 150

175

120 120 120

125

90 90 90 100

64 66 68 70

2 1 1

1

3 3

2 2

4 4 4 3

80 80 90 90

80.00 82.50 85.00 87.50

200 200

225 225

175

175 175 175

150 150 150 150

100 100 110 110

72 74 76 78

1 0 0 0

2

2 2 1

3 3 3 3

90 90 100 100

90.00 92.50 95.00 97.50

225 225 250 250

200 200 200 200

150 150

175 175

110 125 125

125

* For running protection of motors of 1 horsepower or less, see section 4322 of National Electric Code.

** For the grouping of small motors under the protection of a single set of fuses, see section 4343 of National Electric Code. *** High-reactance squirrel-cage motors are those designed to limit the starting current by means of deep-slot secondaries or double-wound secondaries

and are generally started on full voltage.

17 18 19 20

10 10 10 10

12 12 10 10

14 12 12 12

25 25 25 25

21.25 22.50 23.75 25.0

60 60 60 60

45 45 50 50

35 40 40 40

30 30 30 30

22 24 26 28

8 8 8 8

10 10 8

8

10 10 10 10

30 30 35 35

27.50 30.00 32,50 35.00

70 80 80 90

60 60 70 70

45 50 60 60

35 40 40 45

30

32 34 36

6 6 6 6

8 8 6 6

8 8 8 8

40 40

45 45

37.50 40.00 42,50 45.00

90 100 110 110

70 80 90 90

60 70 70 80

45 50 60 60

38 40 42

44

5 5 5 4

6 6 6

5

8 6 6 6

50 50 50 60

47.50 50.00 52.50 55.0

125 125 125 125

100 100 110 110

80 80 90 90

60 60 70 70

46

48 50

52 54

4

4 3 3 3

5 5 5 4 4

6 6 6 6

5

60 60 60 70 ' 70

57.50 60.0 62,50 65,0 67.50

150 150 150

175 175

125 125 125 150 150

100 100 100 110

110

70 80 80 80 90

56 58 60 62

2 2 2 2

4 3 3 3

5 5 5 4

70 70 80 80

70.00 72.50 75.00 77.50

175 175 200 200

150 150 150

175

120 120 120

125

90 90 90 100

64 66 68 70

2 1 1

1

3 3

2 2

4 4 4 3

80 80 90 90

80.00 82.50 85.00 87.50

200 200

225 225

175

175 175 175

150 150 150 150

100 100 110 110

72 74 76 78

1 0 0 0

2

2 2 1

3 3 3 3

90 90 100 100

90.00 92.50 95.00 97.50

225 225 250 250

200 200 200 200

150 150

175 175

110 125 125

125

* For running protection of motors of 1 horsepower or less, see section 4322 of National Electric Code. ** For the grouping of small motors under the protection of a single set of fuses, see section 4343 of National Electric Code. *** High-reactance squirrel-cage motors are those designed to limit the starting current by means of deep-slot secondaries or double-wound secondaries

and are generally started on full voltage.

CONDUCTOR SIZES AND OVERCURRENT PROTECTION FOR MOTORS - Continued

     

Maximum Allowable Rating of Branch Circuit Puses

         

With Code

 
         

Letters

 
       

With Code Letters

Squirrel cage

 

Full load current rating of motor amperes

Minimum size conductor in raceways For conductors in air or for other insulations see Tables A and B

AWG AND MCM

For Running Protection of Motors

With Code Letters

Single-phase and squirrel cage and synchronous. Full voltage, resistor and reactor starting, Code letters F to R inc. Without Code

Single-phase and squirrel cage and synchronous. Full voltage, resistor or reactor starting, Code letters B to E inc. Auto- transformer starting, Code letters F to R inc. Without Code Letters Squirrel cage and synchronous, auto-transformer starting, High reactance squirrel

and synchronous Auto-transformer starting, Code letters B to E inc. Without Code Letters Squirrel cage and synchronous, auto- transformer starting, High reactance

With Code Letters

All motors Code letter A. Without Code Letters DC and wound-rotor motors.

Maximum rating

Maximum setting of

   

of

time-limit

Letters

cage.***

squirrel

 
       

N.E.C.

protective

same as above.

Both not more than

cage.***

 
 

Type R

Type Rp

Type RP

fuses

device

 

30 amperes

Both more than 30

 
       

Amperes

Amperes

   

amperes.

 

Col. No. 1

2

3

4

5

6

7

8

9

10

80

0

1

2

100

100.00

250

200

175

125

82

0

1

2

110

102.50

250

225

175

125

84

0

1

2

110

105.00

250

225

175

150

86

00

1

2

110

107.50

300

225

175

150

88

00

1

2

110

110.00

300

225

200

150

90

00

0

2

110

112.50

300

225

200

150

92

00

0

2

125

115.00

300

250

200

150

94

00

0

1

125

117.50

300

250

200

150

96

00

0

1

125

120.00

300

250

200

150

98

000

0

1

125

122.50

300

250

200

150

100

000

0

1

125

125.00

300

250

200

150

105

000

00

1

150

131.5

350

300

225

175

110

000

00

0

150

137.5

350

300

225

175

115

0000

00

0

150

144.0

350

300

250

175

120

0000

000

0

150

150.0

400

300

250

200

125

0000

000

00

175

156.5

400 ! 350

250

200

130 135 140 145 150

250 250 250 300 300

000 0000 0000 0000 0000

00 00 000 000 000

175 175 175 200 200

162.5 169.0 175.0 181.5

187.5

400 450 450 450 450

350 350 350 400 400

300 300 300 300 300

200 225 225 225 225

155 160 165 170

300 350 350 350

0000 250 250 250

000 000 0000 0000

200 200 225 225

194.0 200.0 206. 213.

500 500 500 500

400 400 450 450

350 350 350 350

250 250 250 300

175 180 185 190

400 400 400 500

300 300 300 300

0000 0000 0000 250

225 225 250 250

219. 225. 231. 238.

600 600 600 600

450 450 500 500

350 400 400 400

300 300 300 300

195 200 210 220

500 500 500 600

350 350 400 400

250 250 300 300

250 250 250 300

244. 250. 263.

275.

600 600

500 500 600 600

400 400 450 450

300 300 350 350

230 240 250 260

600 700 700 750

500 500 500 600

300 350 350 400

300 300 300 350

288. 300. 313. 325.

 

600 600

500 500 500 600

350 400 400 400

270 280 290 300 320

800 900 900 1000 1250

600 600 700 700 750

400 500 500 500 600

350 350 350 400 400

338. 350. 363.

375. 400.

   

600 600 600 600

450 450 450 450 500

340 360 380 400

1500 1750

900 1000 1250 1500

600 700 750 900

450 450 500 500

425. 450.

475. 500.

   

...

600 600 600 600

420 440 460

....

1500 1750

1000 1250 1250

600 600 600

525. 550. 575.

       

480

   

1500

600

600.

       

500

   

1500

 

625.

       
                   


ROUND COPPER WIRE

Gage No.

Bare Diameter

Circular Mils

Square Inch

Ohms per 1000 feet 25° C.

Weight in Ib per 1000 ft.

27

.0142

202

.000158

52.6

.609

26

.0159

253

.000199

417

767

25

.0179

320

.000252

33.0

.971

24

.0201

404

.000317

26.2

1.22

23

.0226

511

.000401

207

1.54

22

.0254

645

.000507

16.4

1.95

21

.0285

812

.000638

13.0

2.46

20

.032

1020

.000804

10.3

3.10

19

.036

1300

.00102

8.14

3.93

18

.040

1600

.00126

6.59

4.85

17

.045

2030

.00159

5.22

6.12

16

.051

2600

.00204

4.07

7.86

15

.057

3250

.00255

3.26

9.82

14

.064

4100

.00322

2.58

12.4

13

.072

5180

.00407

2.04

157

12

.081

6560

.00515

1.61

19.8

11

.091

8280

.00650

1.28

25.0

10

.102

10400

.00817

1.02

31.5

9

.114

13000

.0102

.814

39.3

8

.129

16600

.0131

.634

50.5

7

.144

20700

.0163

.510

62.8

6

.162

26200

.0206

.403

79.4

5

.182

33100

.0260

.319

100.

4

.204

41600

.0327

.254

126.

3

.229

52400

.0412

.202

159.

2

.258

66600

.0523

.159

201.

0

.325

106000

.0830

.100

320.

2/0

.365

133000

.105

.0791

404.

4/0

.460

212000

.166

.0500

650.


Fig. A-l. Magnetization Curves

MULTIPLYING FACTORS FOR CONVERTING D-C RESISTANCE OF LARGE CONDUCTORS AND CABLES TO A-C RESISTANCE

Conductor Size in Circular Mils

Multiplying Factor

25 Cycles

60 Cycles

250,000

 

1.005

300,000

 

1.006

350,000

 

1.009

400,000

 

1.011

500,000

 

1.018

600,000

1.005

1.025

700,000

1.006

1.034

750,000

1.007

1.039

800,000

1.008

1.044

900,000

1.010

1.055

1,000,000

1.012

1.067

1,250,000

1.019

1.102

1,500,000

1.027

1.142

1,750,000

1.037

1.185

2,000,000

1.048

1.233




Last Update: 2010-10-05