Brainscape's Knowledge GenomeTM

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


See full index

3rd 6 Months > PHEP Ch. 23 Transformers > Flashcards

PHEP Ch. 23 Transformers Flashcards

1
Q

A power transformer transfers electrical power from one circuit to a certain frequency and voltage, an to a second circuit at?

A

A different voltage and the same frequency.

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

Transformer polarity markings show?

A

The ends of the windings at which the induced voltages have the same instantaneous polarity.

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

The efficiency of a well designed transformer is?

A

An average of 98 percent.

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

A single phase transformer may have an?

A

Air Core.

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

Compared to the secondary of a loaded step-down transformer, the primary has?

A

Higher Voltage and Lower Current.

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

Potential transformers are instrument transformers used to?

A

Step voltage down.

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

The secondary of a potential transformer should never be?

A

Short-circuited to remove the device it operates from service.

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

Current transformers are instrument transformers used to?

A

Step current down.

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

Current transformers are used with?

A

Ammeters
Watt Meters
Protective Relays

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

When the number of turns or voltage on the secondary of a transformer is greater than that of the primary, it is known as a?

A

Step-Up Transformer.

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

Transformers are classed as static AC machines. True or False?

A

True.

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

Transformers having only one winding are called?

A

Autotransformers.

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

In an energized transformer iron losses are present even if there is no load on the secondary. True or False?

A

True.

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

An autotransformer has?

A

One winding which is composed of both the primary and secondary winding.

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

The core of a transformer is designed…

A

To carry the magnetic field for the introduction of voltages between the primary and secondary windings.

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

The secondary of a current transformer should never be?

A

Opened to remove the device it operates from service.

17
Q

Eddy currents are circulating currents that cause?

A

A loss of energy.

18
Q

In a core type transformer…

A

A section of the primary and secondary windings are wound around each leg of the core.

19
Q

Hysteresis and eddy currents are known as?

A

Iron Losses.

20
Q

Hysteresis can be explained as?

A

Friction of the molecules due to alternating current.

21
Q

Increasing the rate of cooling on a transformer will increase its capacity. True or False?

A

True.

22
Q

The rating of a transformer is usually given in?

A

VA (volt-amperes)
KVA (kilovolt-amperes)
MVA (megavolt-amperes)

23
Q

Transformer oil will lose its dielectric strength rapidly when…

A

Exposed to air or moisture.

24
Q

Bushings are used on transformers to?

A

Serve as entrances into the transformer for the main leads.

25
Q

Taps on a transformer will allow the…

A

Output voltage to be varied.

26
Q

The condition(s) that must be met when transformers are operated in parallel are?

A

Ratio of transformation approximately the same
Voltage rating approximately the same
Polarity must be the same

27
Q

The conservator system is used on transformers to?

A

Preserve the dielectric strength of the transformer oil.

28
Q

A series of street lighting system requires what type of transformer?

A

A constant current transformer.

29
Q

In a transformer the winding which receives the energy inductively is called the?

A

Secondary Winding.

30
Q

In a transformer, excluding the small amount of losses, the induced voltage per turn in the secondary winding is?

A

Equal to the voltage across each turn of the primary winding.

31
Q

In a transformer a _____ must always exist between the primary and the secondary fields to maintain the required primary current to supply the transformer losses and secondary load.

A

Balanced condition.

32
Q

Transformers permit the transfer of electricity between two circuits which are?

A

Completely insulated from each other.

33
Q

When a transformers windings are connected in delta…

A

The line current will be greater than the phase current.

34
Q

When a transformers windings are connected in wye…

A

The line current will be the same as the phase current.

35
Q

In a transformer, both the primary to secondary voltage and turn ratio will vary inversely as the primary…

A

To secondary current ratio.

3rd 6 Months (13 decks)

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