Tables > Motors > Ratings and Settings > Branch Circuit Protective Devices

	Percent of Full-Load Current Type of Motor Nontime Delay Fuse* Dual Element (Time-Delay) Fuse* Instantaneous Trip Breaker Inverse Time Breaker** Single-phase motors 300 175 800 250 AC Polyphase Squirrel Cage - other than Design B energy efficient 300 175 800 250 AC Polyphase - Design B energy efficient 300 175 1100 250 Synchronous 300 175 800 250 Wound Rotor 150 150 800 150 Direct Current 150 150 250 150
For certain exceptions to the values specified, see Sections 430-52 - 430-54. *The values in the Nontime Delay Fuse column apply to Time-Delay Class CC fuses. **The values given in the last column also cover the ratings of nonadjustable inverse time types of circuit breakers that may be modified as in Section 430-52. ***Synchronous motors of the low-torque, low speed type (usually 450 rpm or lower), such as are used to drive reciprocating compressors, pumps, etc., that start unloaded, do not require a fuse rating or circuit-breaker setting in excess of 200% of full-load current.
See also Calculations All-in-One Short Circuit Calculator All-in-One Short Circuit Calculator Guides Determining branch-circuit demand load for cooking equipment Limit conductor load to limit the circuit voltage drop Tables "C" values for conductors for use in short-circuit calculations Definitions Parallel Circuit Millman's Method