Data on Three-phase Alternating Current Motors

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Motor Horsepower		Motor Ampere	Size Breaker	Size Starter	Heater Ampere	Size Wire	Size Conduit
1/2	230V 460	2.2 1.1	15 15	00 00	2.530 1.265	12 12	3/4" 3/4
3/4	230 460	3.2 1.6	15 15	00 00	3.680 1.840	12 12	3/4 3/4
1	230 460	4.2 2.1	15 15	00 00	4.830 2.415	12 12	3/4 3/4
1 1/2	230 460	6.0 3.0	15 15	00 00	6.900 3.450	12 12	3/4 3/4
2	230 460	6.8 3.4	15 15	0 00	7.820 3.910	12 12	3/4 3/4
3	230 460	9.6 4.8	20 15	0 0	11.040 5.520	12 12	3/4 3/4
5	230 460	15.2 7.6	30 15	1 0	17.840 8.740	12 12	3/4 3/4
7 1/2	230 460	22 11	45 20	1 1	25.300 12.650	10 12	3/4 3/4
10	230 460	28 14	60 30	2 1	32.200 16.100	10 12	3/4 3/4
15	230 460	42 21	70 40	2 2	48.300 24.150	6 10	1 3/4
20	230 460	54 27	100 50	3 2	62.100 31.050	6 10	1 3/4
25	230 460	68 34	100 50	3 2	78.200 39.100	4 8	1 ^1/2 1
30	230 460	80 40	125 70	3 3	92.000 46.000	3 8	1 ^1/2 1
40	230 460	104 52	175 100	4 3	119.600 59.800	1 6	1 ^1/2 1
50	230 460	130 65	200 150	4 3	149.500 74.750	00 4	2 1 ^1/2
60	230 460	154 77	250 200	5 4	177.10 88.55	000 3	2 1 1/2
75	230 460	192 96	300 200	5 4	220.80 110.40	250_kcmil 2	2 1/2 1 1/2
100	230 460	248 124	400 200	5 4	285.20 142.60	350_kcmil 0	3 2
125	230 460	312 156	500 250	6 5	358.80 179.40	600_kcmil 000	3 1/2 2
150	230 460	360 180	600 300	6 5	414.00 207.00	700_kcmil 0000	4 2 1/2

*Overcurrent device may have to be increased due to starting current and load conditions. See NEC 430-52, Table 430-152. Wire size based on 75 degrees Celsius terminations and 75 degrees Celsius insulation.
**Overload heater must be based on motor nameplate & sized per NEC 430-32.
***Conduit size based on Rigid Metal Conduit with some spare capacity. For minimum size & other conduit types, see NEC Appendix C.

Wire & conduit size will vary depending on type of insulation & termination listing.
The preceding calculations apply to induction type, squirrel-cage, and wound-rotor motors only.
The voltages listed are rated motor voltages; corresponding nominal system voltages are 220V to 240V, and 440V to 480V.
Hertz: Preferred terminology for cycles per second.
Form coil: Coil made with rectangular or square wire.
Mush coil: Coil made with round wire.
Slip: Percentage difference between synchronous and operating speeds.
Synchronous speed: Maximum speed for A.C. motors or (Frequency * 120) / Poles.
Full load speed: Speed at which rated horsepower is developed.
Poles: Number of magnetic poles set up inside the motor by the placement and connection of the windings.