Online Calculators and Tables to Help You Determine Proper Wire Size
The voltages listed below are standard rated motor voltages. This includes induction-type and synchronous-type three-phase alternating-current motors.
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Full-Load Amps: Three-Phase
Alternating-Current Motors
| Induction-Type Squirrel Cage and Wound Rotor (Amperes) | Synchronous-Type Unity Power Factor (Amperes) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| HP | 115 Volts | 200 Volts | 208 Volts | 230 Volts | 460 Volts | 575 Volts | 2300 Volts | 230 Volts | 460 Volts | 575 Volts | 2300 Volts |
| ½ | 4.4 | 2.5 | 2.4 | 2.2 | 1.1 | 0.9 | -- | -- | -- | -- | -- |
| ¾ | 6.4 | 3.7 | 3.5 | 3.2 | 1.6 | 1.3 | -- | -- | -- | -- | -- |
| 1 | 8.4 | 4.8 | 4.6 | 4.2 | 2.1 | 1.7 | -- | -- | -- | -- | -- |
| 1½ | 12 | 6.9 | 6.6 | 6 | 3 | 2.4 | -- | -- | -- | -- | -- |
| 2 | 13.6 | 7.8 | 7.5 | 6.8 | 3.4 | 2.7 | -- | -- | -- | -- | -- |
| 3 | -- | 11 | 10.6 | 9.6 | 4.8 | 3.9 | -- | -- | -- | -- | -- |
| 5 | -- | 17.5 | 16.7 | 15.2 | 7.6 | 6.1 | -- | -- | -- | -- | -- |
| 7½ | -- | 25.3 | 24.2 | 22 | 11 | 9 | -- | -- | -- | -- | -- |
| 10 | -- | 32.2 | 30.8 | 28 | 14 | 11 | -- | -- | -- | -- | -- |
| 15 | -- | 48.3 | 46.2 | 42 | 21 | 17 | -- | -- | -- | -- | -- |
| 20 | -- | 62.1 | 59.4 | 54 | 27 | 22 | -- | -- | -- | -- | -- |
| 25 | -- | 78.2 | 74.8 | 68 | 34 | 27 | -- | 53 | 26 | 21 | -- |
| 30 | -- | 92 | 88 | 80 | 40 | 32 | -- | 63 | 32 | 26 | -- |
| 40 | -- | 120 | 114 | 104 | 52 | 41 | -- | 83 | 41 | 33 | -- |
| 50 | -- | 150 | 143 | 130 | 65 | 52 | -- | 104 | 52 | 42 | -- |
| 60 | -- | 177 | 169 | 154 | 77 | 62 | 16 | 123 | 61 | 49 | 12 |
| 75 | -- | 221 | 211 | 192 | 96 | 77 | 20 | 155 | 78 | 62 | 15 |
| 100 | -- | 285 | 273 | 248 | 124 | 99 | 26 | 202 | 101 | 81 | 20 |
| 125 | -- | 359 | 343 | 312 | 156 | 125 | 31 | 253 | 126 | 101 | 25 |
| 150 | -- | 414 | 396 | 360 | 180 | 144 | 37 | 302 | 151 | 121 | 30 |
| 200 | -- | 552 | 528 | 480 | 240 | 192 | 49 | 400 | 201 | 161 | 40 |
| 125 | -- | 359 | 343 | 312 | 156 | 125 | 31 | 253 | 126 | 101 | 25 |
| 150 | -- | 414 | 396 | 360 | 180 | 144 | 37 | 302 | 151 | 121 | 30 |
| 200 | -- | 552 | 528 | 480 | 240 | 192 | 49 | 400 | 201 | 161 | 40 |
| 400 | -- | -- | -- | -- | 477 | 382 | 95 | -- | -- | -- | -- |
| 450 | -- | -- | -- | -- | 515 | 412 | 103 | -- | -- | -- | -- |
| 500 | -- | -- | -- | -- | 590 | 472 | 118 | -- | -- | -- | -- |
Note: For synchronous-type motors with 0.9 and 0.8 power factor, there amperes listed in the table should be multiplied by a factor of 1.1 and 1.25, respectively.
Motor Wire Sizing
It is required by the NEC for circuits supplying single motors to have an ampacity rating of greater than or equal to 125% of the full-load ampacity rating of the motor. Branch circuits that contain two or more motors must have wire in which the ampacity rating of the wire must be at least 125% of the full-load current of the largest motor, plus the sum of full-load currents for the rest of the motors. For example, if there are three 15-amp motors in the circuit, the ampacity rating of the wire feeding the circuit must exceed . There are exceptions to this requirement, which would include interlocks of two or more motors to prevent them from running at the same time. Typically, the nominal system voltage for a motor will be above the nameplate voltage to compensate for any voltage drop in the circuit.
| 115 | 120 |
| 230 | 240 |
| 460 | 480 |
| 575 | 600 |
| 4,000 | 4,160 |
| 6,600 | 6,900 |
| 13,200 | 13,800 |
For more details into sizing wire and circuit protection devices for motors, view the Motor Wire Size and Circuit Protection Chart and the Motor Wire Size Calculator.
View wire size charts from the list below.
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