EIAT and NEIEP Test Motor Controls 3

Question 1

In a ladder logic diagram used for motor control, what does a normally closed (NC) contact symbol represent?

Accepted Answer

A contact that is closed during normal (de-energized) operation and opens when energized

Answer

An NC contact passes current in its normal (de-energized) state and opens (interrupts current) when its associated coil is energized or the device is actuated.

Question 2

Which NEC article primarily covers the installation requirements for motors, motor circuits, and motor controllers?

Accepted Answer

Article 430

Answer

NEC Article 430 covers motors, motor circuits, and controllers, including conductor sizing, overcurrent protection sizing, and disconnecting means requirements.

Question 3

What is 'plugging' in the context of motor control?

Accepted Answer

Stopping a motor quickly by momentarily reversing the phase connections while the motor is still running

Answer

Plugging stops a motor quickly by briefly applying reversed phase sequence while the motor is still rotating, which creates a strong braking torque opposing the rotation.

Question 4

A wye-delta (star-delta) starter is used primarily for:

Accepted Answer

Reducing starting current by initially connecting the motor windings in wye, then switching to delta for full-speed operation

Answer

A wye-delta starter reduces starting current to approximately one-third of across-the-line values by first connecting windings in wye, then transitioning to delta for normal operation.

Question 5

What is the function of a control transformer in a motor control panel?

Accepted Answer

To step down the line voltage to a lower, safer control circuit voltage such as 120V

Answer

The control transformer steps down the high line voltage (e.g., 480V) to a safer, lower voltage (typically 120V) dedicated to powering the control components.

EIAT and NEIEP Test Practice Test

EIAT and NEIEP Test Practice Test

EIAT and NEIEP Test Motor Controls 3