Electrical Data

Electrical Terminology

Volt (E) is the unit of electric pressure or electromotive force. It is the potential that will produce a current of 1 ampere through a resistance of 1 ohm. 

Ampere (I) is the unit of electrical current (coulombs per second). 

Ohm (R) is the unit of electrical resistance (volts/ampere). 

Watts (W) and kilowatts (KW) are units of electric power. 

Kilovolt-ampere (KVA) is a measurement of apparent electric power. 

Kilowatt hour (Kwhr) is a unit of electrical energy or work performed. 

Joule (J) is a metric unit of energy: watt per second. 
1 Kwhr = 2,655,000 ft-lb = 1.341 hp-hr = 3413 Btu = 3,600,000 joules. 

Ohm law relationships (direct current) E = IR + W/I = √WR
W = I²R = E²/R = EI
I = E/R = W/E = √W/R
R = E/I = W/I² = E²/W

For electrical formulas, see the chart below. Use the symbols above plus the ones defined in the text above the table.

 

Electrical Formulas

Use the symbols in Electrical Terminology above, plus:
eff = efficiency (expressed as a decimal)
pf = power factor (expressed as a decimal)
hp = horsepower output

 

Required	Direct  current	Alternating current
		Single-phase	3-phase*
KVA	—	IE   1000	1.73 IE  1000
Kilowatts	IE   1000	IE (pf)   1000	1.73 IE (pf)   1000
Horsepower (output)	IE (eff)/746	IE (eff)(pf)/746	1.73 IE (eff)(pf)/746
Joules	IE/sec	IE (eff)(pf)/sec	1.73 IE (eff)(pf)/sec
Amperes (hp known)	746 (hp)/E (eff)	746 (hp)/E (eff)(pf)	746 (hp)/1.73 E (eff)(pf)
Amperes (KW known)	1000 KW/E	1000 KW/E (pf)	1000 KW/1.73 E (pf)
Amperes (kva known)	—	1000 KVA/E	1000 KVA/1.73 E

*For 3-phase systems, E is measured line to line and I is phase current.

 

Properties of Conductors 
 

Size (AWG MCM)	Area circle (mils)	Concentric lay conductors		Bare conductors		DC resistance Ω/M ft at 77°F (25°C)**
		No. of wires	Diameter each wire (inch)	Diameter (inch)	Area (sq inch)	Copper		Aluminum
						Bare	Tin'd
18	1620	—	—	0.0403	0.0013	6.51	6.79	10.7
16	2580	—	—	0.0508	0.0020	4.10	4.26	6.72
14	4110	—	—	0.0641	0.0032	2.57	2.68	4.22
12	6530	—	—	0.0808	0.0051	1.62	1.68	2.66
10	10,380	—	—	0.1019	0.0081	1.018	1.06	1.67
8	16,510	—	—	0.1285	0.0130	0.6404	0.659	1.05
6	26,240	7	0.0612	0.184	0.027	0.410	0.427	0.674
4	41,740	7	0.0772	0.232	0.042	0.259	0.269	0.424
3	52,620	7	0.0867	0.260	0.053	0.205	0.213	0.336
2	66,360	7	0.0974	0.292	0.067	0.162	0.169	0.266
1	83,690	19	0.0664	0.332	0.087	0.129	0.134	0.211
0	105,600	19	0.0745	0.372	0.109	0.102	0.106	0.168
00	133,100	19	0.0837	0.418	0.137	0.0811	0.0843	0.133
000	167,800	19	0.0940	0.470	0.173	0.0642	0.0668	0.105
0000	211,600	19	0.1055	0.528	0.219	0.0509	0.0525	0.0836
250	250,000	37	0.0822	0.575	0.260	0.0431	0.0449	0.0708
300	300,000	37	0.0900	0.630	0.312	0.0360	0.0374	0.0590
350	350,000	37	0.0973	0.681	0.364	0.0308	0.0320	0.0505
400	400,000	37	0.1040	0.728	0.416	0.0270	0.0278	0.0442
500	500,000	37	0.1162	0.813	0.519	0.0216	0.0222	0.0354
600	600,000	61	0.0992	0.893	0.626	0.0180	0.0187	0.0295
700	700,000	61	0.1071	0.964	0.730	0.0154	0.0159	0.0253
750	750,000	61	0.1109	0.998	0.782	0.0144	0.0148	0.0236
800	800,000	61	0.1145	1.030	0.833	0.0135	0.0139	0.0221
900	900,000	61	0.1215	1.090	0.933	0.0120	0.0123	0.0197
1000	1,000,000	61	0.1280	1.150	1.039	0.0108	0.0111	0.0177
1250	1,250,000	91	0.1172	1.289	1.305	0.00863	0.00888	0.0142
1500	1,500,000	91	0.1284	1.140	1.561	0.00719	0.00740	0.0118
1750	1,750,000	127	0.1174	1.526	1.829	0.00616	0.00634	0.0101
2000	2,000,000	127	0.1255	1.630	2.087	0.00539	0.00555	0.00885

** The resistance values given in the last three columns apply only to direct current. When using conductors larger than number 4/0 with alternating current, use the multiplying factors in the table below to compensate for skin effect.

 

Multiplying Factors for Converting Resistance
to 60-Hertz AC Resistance 
 

Size	Multiplying factor
	For nonmetallic sheathed cables in air or nonmetallic conduits		For metallic sheathed cables or all cables in metallic raceways
	Copper	Aluminum	Copper	Aluminum
Up to 3 AWG	1.000	1.000	1.00	1.00
Up to 2 AWG	1.000	1.000	1.01	1.00
Up to 1 AWG	1.000	1.000	1.01	1.00
0	1.001	1.000	1.02	1.00
00	1.001	1.001	1.03	1.00
000	1.002	1.001	1.04	1.01
0000	1.004	1.002	1.05	1.01
250 MCM	1.005	1.002	1.06	1.02
300 MCM	1.006	1.003	1.07	1.02
350 MCM	1.009	1.004	1.08	1.03
400 MCM	1.011	1.005	1.10	1.04
500 MCM	1.018	1.007	1.13	1.06
600 MCM	1.025	1.010	1.16	1.08
700 MCM	1.034	1.013	1.19	1.11
750 MCM	1.039	1.015	1.21	1.12
800 MCM	1.044	1.017	1.22	1.14
1000 MCM	1.067	1.026	1.30	1.19
1250 MCM	1.102	1.040	1.41	1.27
1500 MCM	1.142	1.058	1.53	1.36
1750 MCM	1.185	1.079	1.67	1.46
2000 MCM	1.233	1.100	1.82	1.56