MC II: Lesson 5 - Motor Control Centers

Question 1

The ______ is an efficient method to mount, power, and organize electrical motor control, automation, and power distribution systems.

a. motor control center
b. panelboard
c. switchboard

Answer 1

a. motor control center

Question 2

A typical motor control center section is ______ wide by 90 inches tall, and is 15 to 20 inches deep.

a. 16”
b. 20”
c. 24”

Answer 2

b. 20”

Question 3

The ______ should be used to install, operate, or maintain an MCC.

a. manufacturer’s manuals
b. NEC
c. project specifications

Answer 3

a. manufacturer’s manuals

Question 4

Identify the various parts of a motor control center.

Answer 4

Question 5

Feeder power for an MCC enters the unit from ______.

a. overhead only
b. overhead or underneath
c. underneath only

Answer 5

b. overhead or underneath

Question 6

The fault current withstand rating of an MCC is determined by the highest rated device within the MCC.

True or False

Answer 6

False

Question 7

Type C, MCC Size ______ or smaller units or buckets, are factory-wired from unit-located terminal blocks to the master terminal blocks.

a. 2
b. 3
c. 4

Answer 7

b. 3

Question 8

Power buses in MCCs are typically copper or aluminum.

True or False

Answer 8

True

Question 9

What is the class and type of an MCC consisting of interconnecting units with Size 3 or smaller starters and terminations on terminal blocks mounted on the bottom of each vertical section?

a. Class 1 – Type A
b. Class 2 – Type B-D
c. Class 2 – Type C

Answer 9

c. Class 2 – Type C

Question 10

What is the class and type of an MCC consisting of independent units with wiring connected directly to device terminals internal to the unit?

a. Class 1 – Type A
b. Class 2 – Type B-D
c. Class 2 – Type C

Answer 10

a. Class 1 – Type A

Question 11

What is the class and type of an MCC consisting of interconnecting units with Size 3 or smaller starters and load wiring connected to factory-wired power terminals located immediately adjacent to and accessible from the vertical wireway?

a. Class 1 – Type A
b. Class 2 – Type B-D
c. Class 2 – Type C

Answer 11

b. Class 2 – Type B-D

Question 12

MCC’s with ______ units or buckets use a sliding track and mechanical lever.

a. fixed
b. removable

Answer 12

b. removable

Question 13

Metering compartments in MCCs often require the use of ______ and ______ transformers to condition voltage and current levels for metering devices.

a. control / current
b. differential / auto
c. potential / current

Answer 13

c. potential / current

Question 14

Identify the motor control compartment components of a fixed MCC bucket.

Answer 14

Question 15

In corrosive atmospheres, copper buses in MCCs are often coated with ______ to protect the bus from corrosion.

a. carbon
b. tin
c. zinc

Answer 15

b. tin

Question 16

The defeater mechanism screw or interlock on the door of an MCC unit or bucket serves to prevent the door on the bucket from being opened when the disconnect switch or circuit breaker is on and the unit is energized.

True or False

Answer 16

True

Question 17

The NEMA or IEC enclosure is the primary protection from the environmental elements.

True or False

Answer 17

True

Question 18

If the manufacturer assembled the MCC on a level surface, then installing the MCC on a level surface is not necessary.

True or False

Answer 18

False

Question 19

When performing maintenance on an MCC, what does the presence of ozone odor indicate?

a. Arcing
b. Open circuit
c. Overheating

Answer 19

a. Arcing

Question 20

When performing maintenance on an MCC, what does discoloration of bolted electrical connections and insulation indicate?

a. Arcing
b. Open circuit
c. Overheating

Answer 20

c. Overheating

Question 21

When performing annual MCC maintenance, buckets should be drawn out or removed from the MCC.

True or False

Answer 21

True

Question 22

When performing annual MCC maintenance, it is not necessary to inspect, clean, or replace air filters.

True or False

Answer 22

False