Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Electrical > Test #4 > Flashcards

Test #4 Flashcards

1
Q

A ____ converts electrical energy to mechanical energy.

A

Motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Name two main classifications of ac motors.

A
  • single phase
  • poly phase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the three types of ac induction motors? Describe them.

A
  • split-phase motor: one centrifugal switch
  • capacitor-start motor: has both centrifugal switch and capacitor
  • permanent-split capacitor motor: has only capacitor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Name the three types of dc motors. Describe them.

A
  • shunt-wound motor: shunt field and armature are on different lines
  • series-wound motor: series shunt and armature are on same line
  • compound-wound motor: both motors combined, shunt field on top line while series and armature are on middle line
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

____ a force that produces rotation.

A

Motor Torque

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List four general factors used to make a proper motor selection.

A
  • power source
  • temperature
  • environment
  • load
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Name three factors that affect motor enclosure selection.

A
  • environment
  • supplied equipment
  • availability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Most motors are built to withstand minor ___.

A

Over-loads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Maximum output = ?

A

hp x service factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What four situations determine how circuits are sized?

A
  • circuit supplying a single motor
  • circuit supplying several motors & other loads
  • multi motor & combination-load equipment
  • rating & size of motor load
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Current drawn by a motor is initially large, but stabilizes to the ____ current.

A

Full-load

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What carries 500% of its rating for up to 10 seconds, allowing more time for the current drawn by the motor to stabilize?

A

Time-delay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is read by the power company’s wattmeters for billing purposes?

A

True power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

If the true power and apparent are equal, the power factor would be ____.

A

1 or 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Power companies impose penalties or higher rates for customers whose power factor is below a set limit, normally ____.

A

90%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How are lower power factors imposed?

A

By adding capacitors to the circuit or by reducing the lag between the current & voltage.

17
Q

A ___ regulates the power supply to a motor.

A

Motor controller

18
Q

Motor starters are rated for motor horsepower and ____.

A

Full-load current

19
Q

Name two common classes of starters.

A
  • manual starters
  • magnetic starters
20
Q

Which starter is a simple, mechanical on-off switch?

A

Manual starters

21
Q

Why is it important to be extremely cautious when servicing two-wire circuits?

A

These circuits provide low-voltage release without the protection, so if the motor stops, there’s no way of knowing when it’ll start again.

22
Q

If power is interrupted, a ____ circuit will not automatically restart a motor when power is restored.

A

Three-wire

23
Q

A motor control circuit normally operates at how many volts or less?

A

120 V

24
Q

When several motors are controlled from a central location, it is call a ____.

A

Motor control center

25
Q

The motor ____ circuit carries the electric signals directing the performance of the controller, but it does not carry the main power current.

A

Control

26
Q

List five types of pilot devices.

A
  • float switch
  • limit switch
  • snap switch
  • foot switch
  • pressure switch
27
Q

Electrical systems installed where an interruption of power could result in hazard to life, property, or production are called ____ systems.

A

Emergency

28
Q

Legally required _____ systems are intended to automatically supply power to selected loads in the event of failure of the normal source.

A

Standby

29
Q

Systems intended to supply power to public or private facilities or property where life safety does not depend on the performance the system is called ____ system.

A

Optional standby

30
Q

List three loads for which an emergency power system normally provides power.

A
  • emergency lighting
  • fire pumps
  • ventilation
31
Q

When standard service fails, the ____ switch activates the emergency power system within 10 seconds.

A

Automatic transfer

32
Q

Name five ways emergency power can be supplied.

A
  • storage batteries
  • generators
  • separate service
  • supply tap ahead of main
  • individual unit equipment
33
Q

Batteries used to supply emergency power must be capable of supplying at least ____ of the normal system voltage for at least one and a half hour.

A

87.5%

34
Q

The emergency power generator must produce voltage _____ the normal building supply voltage.

A

Identical to

35
Q

Code requirements for generator installation are found in which article?

A

Article 445

36
Q

List four loads that may be supplied by legally required standby systems.

A
  • heating system
  • ventilation & cooling system
  • sewage system
  • lighting
37
Q

List seven loads that may be included in an optional standby system.

A
  • refrigeration system
  • heater units
  • computers
  • data processing systems
  • communication systems
  • manufacturing processes
  • alarm systems

Electrical (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions