How Many Amps Does a 125 HP Three-Phase Motor Draw?
Verified against NEC 2023, checked against the 2026 edition · Last checked September 7, 2026
A 125 hp three-phase motor draws 312 A at 230 V, 156 A at 460 V and 343 A at 208 V, the table currents for 240 V, 480 V and 208 V systems · Table 430.250. At 460 V its branch-circuit conductors need at least 195 A of ampacity, 125% of the table current · 430.22, and the inverse-time breaker tops out at 400 A · Table 430.52(C)(1). 250% of 156 A is 390 A, rounded up to the next standard rating · 430.52(C)(1)(a). Size the wire and the breaker from these table values, not the nameplate · 430.6(A)(1).
| Table voltage | System | FLC | Conductor min · 430.22 | Max breaker · 430.52(C)(1) |
|---|---|---|---|---|
| 200 V | 200 V | 359 A | 448.75 A | 1000 A |
| 208 V | 208 V | 343 A | 428.75 A | 1000 A |
| 230 V | 220 to 240 V | 312 A | 390 A | 800 A |
| 460 V | 440 to 480 V | 156 A | 195 A | 400 A |
The 230 V and 460 V currents are permitted for 220 to 240 V and 440 to 480 V systems · Table 430.250. Squirrel-cage induction motors; the 575 V column is on the Motor FLC tables page. Wire and breaker are sized from these table values, not the nameplate · 430.6(A)(1). Where 250% of FLC is not a standard rating, the next higher standard rating is shown · 430.52(C)(1)(a).
| Device | Max % of FLC | Computed | Standard size |
|---|---|---|---|
| Inverse-time breaker | 250% | 390 A | 400 A |
Where the computed value is not a standard rating in 240.6(A), the next higher standard rating is permitted · 430.52(C)(1)(a). Breaker ratings start at 15 A. Fuse sizes and instantaneous-trip settings are not shown.
| Conductor | Size | Ampacity | Basis |
|---|---|---|---|
| Copper · 75°C terminals | 3/0 AWG | 200 A | Table 310.16 · 75°C column |
| Aluminum · 75°C terminals | 250 kcmil | 205 A | Table 310.16 · 75°C column |
The small-conductor caps of 240.4(D) do not limit motor branch circuits. Table 240.4(G) sends motor circuit conductors to Article 430, where Part III sets overload and Part IV sets short-circuit and ground-fault protection · 240.4(G). Ground wire from Table 250.122 at the breaker rating. It never needs to be larger than the circuit conductors · 250.122(A).
What changes this answer
Table current, not nameplate · 430.6(A)(1)
Conductor ampacity and the branch-circuit device come from the table value above, not from the nameplate. The nameplate current sizes only the overload protection.
Overload protection · 430.32(A)(1)
Rated or set at no more than 125% of the nameplate amps for a motor with a marked service factor of 1.15 or more or a marked temperature rise of 40°C or less, otherwise 115%. Nameplate, not table.
Round-up rule · 430.52(C)(1)(a)
250% of 156 A is 390 A, not a standard rating in 240.6(A), so the next higher standard rating of 400 A is permitted.
Small-conductor caps · 240.4(G)
The 15, 20 and 30 A caps of 240.4(D) for 14, 12 and 10 AWG copper do not apply here. Motor branch-circuit conductors are governed by Article 430 (Table 240.4(G) lists Parts II through VII), so a 3/0 AWG copper conductor can sit behind a 400 A breaker on this circuit.
Hot locations and shared raceways · 310.15(B)(1), 310.15(C)(1)
The conductor sizes above assume 86°F and no more than three current-carrying conductors. Ambient above 86°F and four or more conductors in one raceway derate the ampacity. Run the wire size calculator with your conditions.
Long runs and voltage drop
Distance does not change the NEC minimum, but past roughly 100 feet voltage drop usually forces a larger conductor. Motors are sensitive to low voltage at start.
Size the whole motor circuit on the job site, offline.
The JobVolt app runs this same verified math with no signal, adds the overload from the nameplate, keeps every calculation in History, and turns it into an inspector-ready PDF submittal on your letterhead.
Common questions
- How many amps does a 125 hp three-phase motor draw?
- 312 A at 230 V, 156 A at 460 V and 343 A at 208 V · Table 430.250. Those columns serve 240 V, 480 V and 208 V systems. The nameplate can differ; wire and breaker are sized from the table · 430.6(A)(1).
- What size breaker for a 125 hp three-phase motor?
- At 460 V, an inverse-time breaker up to 400 A: 250% of 156 A is 390 A · Table 430.52(C)(1), and the next higher standard rating is 400 A · 430.52(C)(1)(a). Overload protection is separate and comes from the nameplate · 430.32(A)(1).
- What size wire for a 125 hp 460 V three-phase motor?
- 3/0 AWG copper with 75°C terminations, or 250 kcmil aluminum. The conductor needs 195 A of ampacity, 125% of the 156 A table current · 430.22, read from Table 310.16.
- What is the full-load current of a 125 hp three-phase motor at 208 V?
- 343 A · Table 430.250. At 200 V the table gives 359 A. At 208 V the conductors need 428.75 A of ampacity · 430.22 and the inverse-time breaker tops out at 1000 A · Table 430.52(C)(1). 250% of 343 A is 857.5 A, rounded up to the next standard rating · 430.52(C)(1)(a).
- Do I use the nameplate amps or the table?
- The table. Conductor ampacity and the branch-circuit short-circuit and ground-fault device are sized from Table 430.250, not from the nameplate · 430.6(A)(1). The nameplate current sizes only the overload device · 430.32(A)(1).