With higher voltage ratings, calculate voltage drop is one of the important factors to keep in mind in order to avoid problems that may occurs and keep our works more accuracy. Here how we calculate voltage drop
STEP 1: Multiply distance (length of 1 cable in feet) by Current
STEP 2: Determine Cable size
STEP 3: Reference the following table from Electrical Protection handbook
STEP 4: Multiply result from step 1 by number we find from table STEP 5: Multiply the result from step 4 by 0.000001
STEP 6: Result from step 5 multiply 100 and divide for voltage source Result from step 6 is voltage loss
Reference:Electrical Protection Handbook by Bussman MFG Division
TABLE
Reference table to calculate voltage drop Electrical Protection Handbook by Bussman MFG Division
Wire Size
Type T.TW (60°C Wire)
Type RH THWN RHW THW (75°C Wire)
Type RHH THHN XHHW (90°C Wire)
Direct Current
PF 3Ø 100%
PF 3Ø 90%
PF 3Ø 80%
PF 3Ø 70%
PF 3Ø 60%
PF 1Ø 100%
PF 1Ø 90%
PF 1Ø 80%
PF 1Ø 70%
PF 1Ø 60%
14 12 10 8
15 20 30 40
15 20 30 45
15 20 30 50
6100 3828 2404 1520
5280 3320 2080 1316
4800 3030 1921 1234
4300 2720 1733 1120
3780 2400 1540 1000
3260 2080 1340 880
6100 3828 2404 1520
5551 3502 2221 1426
4964 3138 2003 1295
4370 2773 1779 1159
3772 2404 1547 1017
6 4 3 2 1
55 70 80 95 110
65 85 100 115 130
70 90 105 120 140
970 614 484 382 306
840 531 420 331 265
802 530 425 339 280
735 487 398 322 270
665 445 368 300 254
590 400 334 274 236
970 614 484 382 306
926 613 491 392 323
850 562 460 372 312
769 514 425 346 294
682 464 385 317 273
0 00 000 0000
125 145 165 195
150 175 200 230
155 185 210 235
241 192 152 121
208 166 132 105
229 190 157 131
224 188 158 135
214 181 155 134
202 173 150 132
241 192 152 121
265 219 181 161
259 217 183 156
247 209 179 155
233 199 173 152
250M 300 350 400
215 240 260 280
255 285 310 335
270 300 325 360
102 85 73 64
89 74 63 55
118 104 94 87
123 111 101 95
125 112 105 98
123 113 106 100
103 86 73 64
136 120 108 100
142 128 117 110
144 130 121 113
142 131 122 116
500M 600M 700M 750M
320 355 385 400
380 420 460 475
405 455 490 500
51 43 36 34
45 38 33 31
76 69 64 62
85 79 74 72
90 85 80 79
92 87 84 82
52 44 38 36
88 80 74 72
98 91 86 83
104 98 92 91
106 101 971 95
800M 900M 1000M
410 435 455
490 520 545
515 555 585
32 28 26
29 26 23
61 57 55
71 68 66
76 74 72
81 78 76
33 30 27
70 66 63
82 78 76
88 85 83
93 90 88
THIS TABLE ONLY APPLY FOR COPPER CONDUCTORS IN IRON CONDUIT
EXAMPLE:
Determine voltage drop for No-6 copper wire in 180 feet of iron conduit-3 phase, 40amp. load at 80% power factor.
Multiply feet by Amperes: 180 x 40 = 7200 Multiply this number by number from table for No.6 wire three-phase at 80%power factor: 7200 x 735 = 5292000 5292000 x 0.000001 = 5.292 Volts
(for a 240 volt circuit the percent voltage drop is 5.92 x 100 : 240 = 2.21%)
Reference
Electrical Protection Handbook by Bussman MFG Division
