Electrical Final

Question 1

Do you need to replace an overload when it trips?

Answer 1

No

Question 2

Why can’t manual contactors be used to start and stop motors?

Answer 2

No overload protection.

Question 3

If resistance in contacts increases, current ___

Answer 3

Decreases

Question 4

Does ambient temperature play a large role in tripping overloads

Answer 4

Yes

Question 5

If ambient temperature is high, will overloads trip quicker or slower?

Answer 5

Quicker

Question 6

What is the advantage of double break contacts over single break contacts?

Answer 6

Higher current rating

Question 7

Why are silver alloy contacts better than copper?

Answer 7

Stronger and more arc resistance.

Question 8

If a fuse or circuit breaker directly opens a circuit when the current limit is reached, do overload heaters open and break the circuit when their current limit is reached?

Answer 8

No

Question 9

What type of relay resets quickly without requiring any cool down?

Answer 9

Magnetic

Question 10

What are the advantages with drum switches?

Answer 10

No need for interlocking, and the operator must keep eyes on the moving equipment.

Question 11

How are mechanical interlocks shown in a print?

Answer 11

Dashed lines between forward and reverse coil.

Question 12

Are control and power circuit voltages typically the same?

Answer 12

No

Question 13

Why aren’t drum switches considered motor starters?

Answer 13

No overloads

Question 14

What are the 2 disadvantages to direct hardwiring?

Answer 14

Time consuming and hard to troubleshoot.

Question 15

Can you always check fuses, regardless of power?

Answer 15

Yes

Question 16

What is the function of brushes?

Answer 16

Connect the armature to an external power source

Question 17

What are the labels of the 2 wires coming out of a Permanent Magnet DC motor?

Answer 17

A1
A2

Question 18

What are the 2 names used for the rotating part of a stepper motor?

Answer 18

Armature and Rotor

Question 19

What are the 2 names for the stationary part of a stepper motor?

Answer 19

Stator and Field

Question 20

What causes the high current that can damage the switching contacts/device?

Answer 20

The collapse of stator coil voltage

Question 21

What device is used to provide feedback about the position of the motor shaft to the control circuit?

Answer 21

Encoder

Question 22

Can there be work if no movement occurs?

Answer 22

No

Question 23

Can there be torque if no movement occurs?

Answer 23

Yes

Question 24

How many watts does a 2HP motor use?

Answer 24

1492W

Question 25

What usually wears out first in a DC motor, and requires occasional service?

Answer 25

Brushes

Question 26

What usually wears out second on a DC motor and requires occasional service?

Answer 26

Commutator

Question 27

What is developed in a wire loop in a magnetic field?

Answer 27

Torque

Question 28

What are the stationary windings of a DC motors called?

Answer 28

Field Windings

Question 29

What are the rotating windings of a DC Motor called?

Answer 29

Armature

Question 30

What is the stationary coil of an AC motors called?

Answer 30

Stator

Question 31

What is the rotating coil of an AC motors called?

Answer 31

Rotor

Question 32

Can a shaded-pole motor be reversed?

Answer 32

No

Question 33

What is the function of the capacitor in single phase motors?

Answer 33

Extra torque for starting and/or running

Question 34

When a motor application requires a motor to be cycled often, what two rated specifications on the motor nameplate should be increased from the normal rating?

Answer 34

Temperature Rise and Service Factor

Question 35

Does a voltage measurement at the motor indicate whether the motor is underloaded, fully loaded, or overloaded?

Answer 35

No

Question 36

If T2 and T5 measure 20Ω when testing the windings of a 3 phase, delta-connected, dual-voltage motor with an ohmmeter, what should the reading be between T5 and T7?

Answer 36

40Ω (Double your ohmic value)

Question 37

What type of motor is used for fractional HP of 1/20 to 1/3.

Answer 37

Split Phase

Question 38

When ringing out 480VAC for high voltage, should all windings have the same ohmic value?

Answer 38

Yes

Question 39

Can you check the control fuses if the power circuit is not working?

Answer 39

Yes

Question 40

When ringing out a DC motor from any phase to the motor frame (ground), what should you read?

Answer 40

OL

Question 41

Do all ungrounded conductors have to have able to be disconnected?

Answer 41

Yes

Question 42

Can all hots, which feed switches, in a motor starter circuit be daisy chained together?

Answer 42

Yes

Question 43

What does a red control wire in a panel indicate?

Answer 43

Power is fed from inside the panel

Question 44

What does a yellow control wire in a panel indicate?

Answer 44

Power is fed from outside the panel

Question 45

Are the still hot components in an open knife switch?

Answer 45

Yes

Question 46

Will coils in 120VAC or 250VDC have higher resistance?

Answer 46

250VDC

Question 47

What happens to contacts if resistance increases?

Answer 47

Heat builds, causing wear and damage to the contacts

Question 48

What is the formula for short term amp rating on a motor?

Answer 48

FLC x Service Factor