NEC 2011: Table 430.52

 

Max Rating of Motor Branch-Circuit Short Circuit and Ground-Fault Protective Devices
  Percentage of Full-Load Current
Type of Motor Non Time
Delay
Fuse
Dual Element (Time Delay) Fuse Instantaneous Trip
Breaker
Inverse
Time
Breaker
Single-phase motors 300 175 800 250
AC Polyphase other than wound-rotor 300 175 800 250
Squirrel Cage - other than Design B 300 175 800 250
Design B
energy efficient
300 175 1100 250
Synchronous 300 175 800 250
Wound Rotor 150 150 800 150
Direct Current (constant voltage) 150 150 250 150

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