Motors and Motor Circuits Flashcards

Per NEC Table 430.248, what is the full-load current of a 5 HP, single-phase, 230V motor?

Answer: 28 amperes

NEC Table 430.248 lists the full-load current of a 5 HP, single-phase, 230V motor at 28 amperes.

Per NEC 430.22, what is the minimum conductor ampacity for a single motor branch circuit?

Answer: 125% of motor FLC

NEC 430.22(A) requires branch-circuit conductors supplying a single motor to have an ampacity of not less than 125% of the motor full-load current from the applicable table.

What is the maximum size inverse-time circuit breaker permitted for branch-circuit protection of a single-phase motor per NEC 430.52?

Answer: 250% of FLC

NEC Table 430.52 permits inverse-time circuit breakers up to 250% of the motor FLC for standard motor branch-circuit short-circuit and ground-fault protection.

Per NEC 430.32, what is the maximum overload protection for a motor with a service factor of 1.15 or greater?

Answer: 125% of nameplate current

NEC 430.32(A)(1) limits overload protection to 125% of the motor nameplate full-load current for motors with a service factor of 1.15 or greater.

Per NEC 430.102, a motor disconnecting means must be located where relative to the motor?

Answer: Within sight from the motor location and the controller

NEC 430.102(A) and (B) require the motor disconnect to be within sight from the controller location, and 430.102(B) requires a disconnect within sight from the motor.

What is the purpose of motor overload protection separate from the branch circuit breaker?

Answer: To protect the motor windings from sustained overcurrent that would cause overheating

Motor overload protection specifically protects the motor windings from damage due to sustained overcurrent conditions that are below the branch-circuit breaker's trip point.