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

A contact that is open during normal (de-energized) operation

Answer

A contact controlled exclusively by an external timer relay

Answer

A contact that can only be reset manually after tripping

Question 2

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

Accepted Answer

Article 430

Answer

Article 210

Answer

Article 445

Answer

Article 460

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

Connecting additional loads to a motor control panel bus

Answer

Inserting a plug-in contactor module into a motor control center

Answer

Testing motor circuit continuity with a plug-type test instrument

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

Providing continuous variable speed control for large induction motors

Answer

Converting three-phase motors to operate on a single-phase supply

Answer

Providing dynamic braking to stop a large motor quickly and safely

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

To step up the voltage from the utility feed to the motor rated voltage

Answer

To isolate the motor windings from the power supply during safety testing

Answer

To convert three-phase power into single-phase for small control devices

Question 6

According to NEC Article 430, the branch circuit conductors supplying a single continuous-duty motor must have an ampacity of at least:

Accepted Answer

125% of the motor full-load current (FLC)

Answer

100% of the motor full-load current (FLC)

Answer

115% of the motor full-load current (FLC)

Answer

150% of the motor full-load current (FLC)

Question 7

In a motor control center (MCC), what is the purpose of a 'bucket'?

Accepted Answer

A removable compartment containing the starter, overload relay, and associated components for a single motor circuit

Answer

The main bus compartment where the incoming power feed connects to the MCC

Answer

A grounding electrode conductor assembly for the entire MCC enclosure

Answer

A dedicated space reserved for future expansion of the motor control center