Electrical Motors - Full Load Amps

Full load amps for single and 3-phase 460 volts, 230 volts and 115 volts electric motors.

As a "rules of thumb" amps horsepower rating can be estimated to

115 volts motor - single-phase : 14 amps/hp
230 volts motor - single-phase : 7 amps/hp
230 volts motor - 3-phase : 2.5 amps/hp
460 volts motor - 3-phase : 1.25 amps/hp

Always check nameplate information before designing protective devices, wiring and switch gear.

Electric motor

Single-Phase Motors - HP and Full-Load Currents

A motor of a given rated horsepower is expected to deliver that quantity of mechanical power at the motor shaft. Be aware that the motor efficiency is not calculated in to the values for kW and amps below. Motor efficiency must be considered to avoid undersized power supply.

Single-Phase Electrical Motors - Full Load Amps
Power		Full Load Current (amp)
(hp)	(kW)	115 V	208 V	230 V
1/6	0.13	4.4	2.4	2.2
1/4	0.19	5.8	3.2	2.9
1/3	0.25	7.2	4.0	3.6
1/2	0.38	9.8	5.4	4.9
3/4	0.56	13.8	7.6	6.9
1	0.75	16	8.8	8
1 1/2	1.1	20	11	10
2	1.5	24	13.2	12
3	2.3	34	18.7	17
5	3.8	56	30.8	28

Note that most electric motors are designed to run at 50% to 100% of rated load and that maximum efficiency usually is near 75% of rated load. For a 1 horsepower (hp) motor the load should typically be in the range 1/2 to 1 hp with maximum efficiency at 3/4 hp.

Typical load ranges:

acceptable for a short-period: 20 - 120%
acceptable for operating: 50 - 100%
optimum efficiency: 60 - 80%

A motor with a service factor can occasional be overloaded. Overloading will over time reduce motor efficiency.

Three-Phase Motors - HP and Full-Load Currents

Three-Phase Electrical Motors - Full Load Amps
Power		Full-Load Current (amp)
Power		Induction Type Squirrel-Cage and Wound Motor					Synchronous Type Unity Power Factor
(hp)	(kW)	115 V	230 V	460 V	575 V	2300 V	230 V	460 V	575 V	2300 V
1/2	0.38	4	2	1	0.8
3/4	0.56	5.6	2.8	1.4	1.1
1	0.75	7.2	3.6	1.8	1.4
1 1/2	1.1	10.4	5.2	2.6	2.1
2	1.5	13.6	6.8	3.4	2.7
3	2.3		9.6	4.8	3.9
5	3.8		15.2	7.6	6.1
7 1/2	5.6		22	11	9
10	7.5		28	14	11
15	11		42	21	17
20	15		54	27	22
25	19		68	34	27		53	26	21
30	23		80	40	32		63	32	26
40	30		104	52	41		83	41	33
50	38		130	65	52		104	52	42
60	45		154	77	62	16	123	61	49	12
75	56		192	96	77	20	155	78	62	15
100	75		248	124	99	26	202	101	81	20

1 hp (English horse power) = 745.7 W = 0.746 kW = 550 ft lb/s = 2,545 Btu/h = 33.000 ft lb/m = 1.0139 metric horse power ~= 1.0 KVA

Direct Current Motors - Power and Full Load Currents

DC Electrical Motors - Full Load Amps
Power		Direct Current (A)
(hp)	(kW)	230 V	440 V
1/4	0.19	0.81	0.42
1/3	0.25	1.1	0.56
1/2	0.37	1.6	0.85
3/4	0.56	2.4	1.3
1	0.75	3.2	1.7
1 1/2	1.1	4.9	2.5
2	1.5	6.5	3.4
3	2.2	9.7	5.1
5	3.7	16	8.5
7 1/2	5.6	24	13
10	7.5	32	17
15	11	49	25
20	15	65	34
30	22	97	51
50	37	162	85
75	56	243	127
100	75	324	170