Motor Branch-Circuit Protection
Maximum short-circuit and ground-fault protective device rating from the table full-load current [1] and the Table 430.52 percentages, which are from the 2017 edition [2]; full-load currents and standard ratings are from the 2023 edition [1]. See also the Motor Starting Current and Circuit Breaker/Fuse Sizing calculators.
Synchronous and dc motors are not in the picker (this site has no full-load currents for them), nor are motors over 1000 V, which Article 430 Part XI covers.
Full-Load Current, Single-Phase Motors — Table 430.248
| hp | 115 V | 200 V | 208 V | 230 V |
|---|
Amperes, NEC 2023 [1]. Use these table values, not the nameplate current, to size conductors and protection (430.6(A)(1)).
Full-Load Current, Three-Phase Motors — Table 430.250
| hp | 115 V | 200 V | 208 V | 230 V | 460 V | 575 V | 2300 V |
|---|
Amperes, induction motors (squirrel cage and wound rotor), NEC 2023 [1]; “—” = no table entry. The table’s synchronous-motor columns are not included.
Locked-Rotor Code Letters — Table 430.7(B)
| Code letter | Locked-rotor kVA per hp |
|---|
Maximum Motor Branch-Circuit Protection — Table 430.52
| Type of motor | Percent of full-load current | |||
|---|---|---|---|---|
| Nontime-delay fuse1 | Dual-element (time-delay) fuse1 | Instantaneous-trip breaker | Inverse-time breaker2 | |
NEC 2017 [2]. 1 Also used for time-delay Class CC fuses. 2 Also covers nonadjustable inverse-time breakers, which may be modified under 430.52(C)(1) Exc. No. 1 and 2. 3 200 % at most for low-torque, low-speed synchronous motors (usually 450 rpm or less) that start unloaded. Exceptions: 430.54.
Standard Ampere Ratings — Table 240.6(A)
| Fuses and inverse-time circuit breakers (A) |
|---|
NEC 2023 [1], which added the 10 A rating.