Brainscape's Knowledge GenomeTM

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


See full index

Plumbing Year 4 > Single phase motors and Transformers > Flashcards

Single phase motors and Transformers Flashcards

1
Q

The motor that has a rotor that spins at the same speed as the magnetic field is the:

Shaded pole

Resistance split-phase induction

Synchronous

Permanent-split capacitor

A

Synchronous

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

The motor with the greatest starting torque is the:

Shaded pole

Resistance split-phase induction

Capacitor-start Induction

Permanent-split capacitor

A

Capacitor-start Induction

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

On a motor name plate, frame type refers to;

the manufacturers specifications & dimensions of this motor

model & serial number of the motor

the number of poles in the stator windings

this is a psychoanalytic term & does not refer to motors

A

the manufacturers specifications & dimensions of this motor

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

Why are motor rotors made of thin sheets of metal laminated together?

Lower manufacturing costs

Lighter weight

Better heat dissipation

It increases efficiency, by reducing Eddy Currents

A

It increases efficiency, by reducing Eddy Currents

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

Why do the maximum voltage ratings on capacitors rarely correspond with common line voltage? (ex. 340-volt rating for a 240-vac motor)

A safety factor is added in

To compensate for line loss

Capacitors are rated for peak voltage

Capacitors have no voltage rating

A

Capacitors are rated for peak voltage

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

How can you reverse the rotation of a shaded pole motor?

Remove the motor, and reinsert it into the stator at 180 degrees

Reverse the main electrical connections

Reverse the start capacitor

It can’t be done

A

Remove the motor, and reinsert it into the stator at 180 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

A primary resistance starter starts a motor with a resistance __ _____ with the main motor windings.

in parallel

in conjunction

in proximity

in series

A

in parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The term “Class 2 Transformer” is defined in;

Section 16 of the Canadian Electrical Code

Modern Refrigeration

Book of the Dead

ASHRAE

A

Section 16 of the Canadian Electrical Code

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

Of the motors listed, which has the largest horsepower rating?

Capacitor-start Induction

Resistance Split-phase Induction

Universal

Shaded pole

A

Capacitor-start Induction

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

NEMA is an acronym for……

National Electronic Manufacturers Association

Nashville Election Makers Affiliation

Neutered and Emasculated Mammals Action Committee

National Electrical Manufacturers Association

A

National Electrical Manufacturers Association

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two types of bearings used in most motors?

Slip bearings and ball bearings

Needle bearings and roller bearings

Sleeve bearings and ball bearings

Roller bearings and slip bearings

A

Sleeve bearings and ball bearings

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

How many electrical degrees apart are the start and run windings on a permanent-split capacitor motor?

15-45 degrees

25-75 degrees

30-40 degrees

80-90 degrees

A

80-90 degrees

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

From the list below, select the motor with the greatest starting torque:

Shaded pole

Universal

Resistance Split-phase Induction

Permanent-split Capacitor

A

Universal

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

On a capacitor-start induction motor the angular phase displacement is created by:

The Run Capacitor

Centrifugal Switch

The Start Capacitor

Resistor in series with the windings

A

The Start Capacitor

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

A centrifugal starting switch is designed to open at approximately _______ of full load current.

65-70%

70-75%

85-90%

95-100%

A

70-75%

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

How are the start windings connected on a 120/240-volt single phase motor, when the motor is connected to lower voltage?

Series / parallel

Parallel

Series

None of the Above

A

Parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is the direction of rotation of a motor determined?

Viewing the motor from the front

Viewing the motor from the back

Viewing the motor from lead end

Viewing the motor from opposite sides

A

Viewing the motor from lead end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is the rotation of a resistance-start induction motor normally reversed?

Reverse the start winding connections.

Reverse the run winding connections.

Physically flip the motor 180 degrees.

Switch the connections on the start capacitor.

A

Reverse the start winding connections.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which document describes the rules by which a gasfitter may do work?

B149.1

B149.2

B149.3

All the above

A

All of the above

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What would the total capacitance be for three 30 µF capacitors connected in parallel?

10 µF

30 µF

90 µF

You can’t do that!!!!

A

90 µF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What type of single-phase motor does not require a starting switch?

None do

Permanent-split capacitor

Resistance split-phase induction

Universal

Capacitor-start induction

A

Permanent-split capacitor

22
Q

The name plate on a 60 Hz single phase motor is 850 rpm. The motor must have:

two poles

four poles

six poles

eight poles

A

eight poles

23
Q

Which of the following is most likely a start capacitor?

145 µF, electrolytic (oil filled)

90 µF, dielectric (dry)

25 µF, dielectric (dry)

7.5 µF, electrolytic (oil filled)

A

90 µF, dielectric (dry)

24
Q

A motor can be installed in an explosive atmosphere as long as it is of a fully enclosed type.

True
False
A

False

25
Q

On a motor name plate, ID number refers to;

Frame Type of motor

Model & Serial Number of the motor

The number of poles in the stator windings

This is a psychoanalytic term & does not refer to motors

A

Model & Serial Number of the motor

26
Q

What is the purpose of the Safety Codes Act?

To protect the occupants and users of a building.

To provide public safety

It makes it mandatory to pull a permit on every job

It states that a gasfitter can work on equipment over 400,000 BTU’s

A

To provide public safety

27
Q

What amount of current causes ventricular fibrillation of the heart?

100 to 200 mA

15 A

15 to 20 mA

over 200 mA

A

100 to 200 mA

28
Q

The capacitor of a capacitor-start motor is rated for:

short-time duty and is connected in series with the auxiliary winding

continuous duty and is connected in parallel with the auxiliary winding

continuous duty and is connected in series with the auxiliary winding

short-time duty and is connected in parallel with the auxiliary winding

A

short-time duty and is connected in series with the auxiliary winding

29
Q

When there is a comparable motor size and load, what is the starting torque of a capacitor-start motor compared to a resistance split-phase motor?

higher

lower

the same

dependent upon the load

A

higher

30
Q

Single-phase motors are more efficient than three-phase motors of comparable horsepower.

True
False
A

False

31
Q

Which testing device listed below is used to verify the motor insulation integrity?

Amp meter

Megger

Ohm meter

Frogger

A

Megger

32
Q

What are two ways a transformer may be short circuited?

overheating, overloading

accidental contact of terminals, overuse

cycling of controls, using wires which are too large

wiring heating controls in improper sequence, short circuiting a gas valve to check its operation

A

overheating, overloading

33
Q

What do manufacturers recommend as a maximum loading factor of the devices that are connected to the secondary side of a dry transformer used for controls?

100 %

48 VA

2 amps

80 %

A

80 %

34
Q

What is the purpose of laminating the core of a dry transformer?

It allows smaller sections of material to be used.

It makes the transformer less expensive to manufacture.

It keeps eddy losses to a minimum.

It strengthens the core.

A

It keeps eddy losses to a minimum.

35
Q

How are the laminations of a transformer core kept electrically separate from each other?

varnishing each section or place paper between the layers and varnish the sections.

place plastic strips between them.

laminations are not electrically separated.

place laminate between the individual core sections.

A

varnishing each section or place paper between the layers and varnish the sections.

36
Q

Which of the following conditions is most likely to be the cause of primary windings opening in a step-down transformer?

high current flow in the secondary windings

high voltage supplied to the primary windings

AC transformer is connected to DC supply source

transformer rated as type F is used in a type A heat environment

A

high current flow in the secondary windings

37
Q

A 14 AWG stranded wire can carry more current than a 14 AWG solid wire.

True
False
A

False

38
Q

The voltage supplied to a circuit is 24 volts, what is the amperage if the resistance draw of the circuit is 80 ohms?

0.03 amps

0.3 amps

3 amps

3.33 amps

A

0.3 amps

A=v/r

39
Q

What do manufacturers recommend as a maximum loading factor of the devices that are connected to the secondary side of a dry transformer used for controls?

100 %

48 VA

2 amps

80 %

A

80%

40
Q

Assume a high limit is connected to line voltage. If the limit opens, what voltage will be read ACROSS the control?

24 VAC

120 VAC

12 VDC

0 VAC

A

120 VAC

41
Q

A Transformers maybe AC or DC!

True if rated for 30 volts or less.

True if rated for 24 volts or less.

Yes it may be DC

AC only

A

AC only

42
Q

Why is it important to zero an analog meter each time you are going to make a resistance reading?

This procedure ensures the meter will be starting from zero for each resistance scale.

This check establishes the condition of the meter’s internal batteries.

This check establishes zero electrical flow in the circuit.

Zeroing the meter allows you to ensure the meter is working properly.

A

This check establishes the condition of the meter’s internal batteries.

43
Q

Static charges accumulate on insulator material!

True
False
A

True

44
Q

What is the maximum voltage unbalance allowable?

2%

5%

10%

12%

A

10%

45
Q

What is reactive power in relation to the output of a transformer?

The transformer reacts to the power load placed on it.

The transformer reacts to the thermostat.

Power is used to create an electromagnetic field

Power causes a direct reaction such as turning on a switch starts an electric motor.

A

Power is used to create an electromagnetic field

46
Q

According to the law of Repulsion and Attraction;

Unlike poles repel and like poles attract.

Like poles repel and unlike pole attract.

A

Like poles repel and unlike pole attract.

47
Q

What is the maximum permissible amperage draw of the secondary side of a transformer with 24-volt output and a 80 VA rating?

0.133 A

1.33 A

0.33 A

3.33 A

A

3.33 A

AD = VA / V

48
Q

Determine the load voltage if the primary coil has 120 Volts with 240 turns and the secondary has 1200 turns?

24 Volts

120 Volts

1200 Volts

600 Volts

A

600 volts

49
Q

When looking at a transformer from the low-voltage side, the standard H1 terminal position is located at:

the upper right-hand corner

the lower right-hand corner

the upper left-hand corner

the lower left-hand corner

A

the upper left-hand corner

50
Q

What are control transformers sized to?

supply voltage

load voltage

load current

VA/kVA rating

A

VA/kVA rating

51
Q

What design feature of a current limiting transformer prevents any increase in secondary current when core saturation is near its peak?

High resistance secondary coil

Air gap

Laminated core

None of the above

A

Air gap

52
Q

Which of the transformer designs listed below has the least amount of flux leakage?

Core Type

H Type

Shell type

U type

A

H type

Plumbing Year 4 (28 decks)

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