Motors and Controls Flashcards
6 cards from real Electrician practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Motors and Controls flashcards as text
What NEC article covers the installation of motors, motor circuits, and controllers?
Answer: Article 430
NEC Article 430 covers all aspects of motor circuits including conductors, overcurrent protection, controllers, and disconnecting means.
What is the purpose of a motor starter?
Answer: To limit inrush current and provide overload protection when starting a motor
A motor starter limits the high inrush current during startup and provides thermal overload protection during operation.
According to the NEC, motor branch circuit conductors must be sized at what minimum percentage of the motor's full-load current (FLC)?
Answer: 125%
NEC 430.22 requires motor branch circuit conductors to be sized at no less than 125% of the motor's full-load current.
What is the function of a thermal overload relay in a motor control circuit?
Answer: To protect the motor windings from excessive heat due to overload
A thermal overload relay monitors motor current and trips to disconnect the motor if it draws excessive current that could overheat and damage the windings.
What type of motor uses both a start winding and a run winding?
Answer: Single-phase split-phase motor
A single-phase split-phase motor uses a start winding (with higher resistance) to create the phase shift needed for starting torque.
What is the maximum rating of an inverse time circuit breaker used to protect a motor branch circuit per the NEC?
Answer: 250% of motor FLC
NEC Table 430.52 allows inverse time (standard) circuit breakers to be sized up to 250% of the motor's full-load current for short-circuit protection.