Electrician Motors and Controls

Question 1

What NEC article covers the installation of motors, motor circuits, and controllers?

Accepted Answer

Article 430

Answer

NEC Article 430 covers all aspects of motor circuits including conductors, overcurrent protection, controllers, and disconnecting means.

Question 2

What is the purpose of a motor starter?

Accepted Answer

To limit inrush current and provide overload protection when starting a motor

Answer

A motor starter limits the high inrush current during startup and provides thermal overload protection during operation.

Question 3

According to the NEC, motor branch circuit conductors must be sized at what minimum percentage of the motor's full-load current (FLC)?

Accepted Answer

125%

Answer

NEC 430.22 requires motor branch circuit conductors to be sized at no less than 125% of the motor's full-load current.

Question 4

What is the function of a thermal overload relay in a motor control circuit?

Accepted Answer

To protect the motor windings from excessive heat due to overload

Answer

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.

Question 5

What type of motor uses both a start winding and a run winding?

Accepted Answer

Single-phase split-phase motor

Answer

A single-phase split-phase motor uses a start winding (with higher resistance) to create the phase shift needed for starting torque.

Electrician Practice Test

Electrician Practice Test

Electrician Motors and Controls