Deck 18: Single-Phase Transformers

Question 1

An isolation transformer whose main purpose is to reduce voltage spikes will have a turns ratio of ____.

A) 1 to 1
B) 1 to 5
C) 5 to 1
D) 2 to 1

Answer 1

A

Question 2

A(n) ____________________ is a magnetically operated machine that can change values of voltage, current, and impedance without a change of frequency.

Answer 2

transformer

Question 3

Primary transformer windings are labeled with the letter ____.

A) S
B) X
C) P
D) H

Answer 3

D

Question 4

A good rule for any transformer is that ____ in must equal ____ out.

A) voltage, voltage
B) power, power
C) amperage, amperage
D) resistance, resistance

Question 5

When testing a transformer, if one lead of an ohmmeter is connected to a primary winding lead and the other is connected to a secondary winding lead, you are checking the transformer for ____.

A) shorted windings
B) grounds
C) continuity
D) voltage

Question 6

Secondary windings of transformers are labeled with the letter ____.

A) S
B) X
C) P
D) H

Question 7

If a transformer has 1000 turns in the primary winding and 100 turns in the secondary winding, the turns ratio of this transformer is ____.

A) 1 to 10
B) 10 to 1
C) 100,000 to 1
D) 10,000 to 1

Question 8

____ are one-winding transformers.

A) Control transformers
B) Autotransformers
C) Distribution transformers
D) Isolation transformers

Question 9

The amount of core material needed for a particular transformer is determined by the ____ rating of the transformer.

A) voltage
B) amperage
C) power
D) resistance

Question 10

____ are often used by power companies to provide voltage regulation to large power lines.

A) Isolation transformers
B) Distribution transformers
C) Control transformers
D) Autotransformers

Question 11

All values of a transformer are ____ its turns ratio.

A) the square of
B) the square root of
C) equal to
D) proportional to

Question 12

The polarity of transformer windings can be determined by connecting them as a(n) ____ and testing them for additive or subtractive polarity.

A) isolation transformer
B) control transformer
C) distribution transformer
D) autotransformer

Question 13

The ability of one coil to induce a voltage into another coil is called ____ induction.

A) excitation
B) ratio
C) voltage
D) mutual

Question 14

When testing a transformer, if one ohmmeter lead is connected to a transformer winding and the other is connected to the transformer frame, you are testing the transformer for ____.

A) shorted windings
B) grounds
C) continuity
D) voltage

Question 15

The polarity notation used for transformers with more than one primary or secondary winding is a ____.

A) dot
B) line
C) dotted line
D) letter X

Question 16

The ____ current is the amount of current required to magnetize the core of the transformer.

A) start-up
B) control
C) excitation
D) ratio

Question 17

The transformer ____ is determined by calculating the percentage of variable voltage as compared to the rated voltage of the high voltage winding.

A) rating
B) voltage
C) impedance
D) amperage

Question 18

If a transformer has several taps on the primary winding and no taps on the secondary winding, it can be connected to different primary voltages without changing the value of the secondary ____.

A) amperage
B) resistance
C) voltage
D) wattage

Question 19

In a distribution transformer, the center tap is grounded and becomes the ____ conductor.

A) distribution
B) ungrounded
C) grounding
D) neutral

Question 20

When testing a transformer, if one ohmmeter lead is connected to the lead of a transformer winding and the other ohmmeter lead is connected to the other lead of the same winding, you are testing the transformer for ____.

A) shorted windings
B) grounds
C) continuity
D) voltage

Question 21

_____________________ leakage is the amount of magnetic flux lines that do not follow the metal core and are lost to the surrounding air.

Question 22

____________________ are often connected in series with a low-impedance load to prevent inrush current from becoming excessive.

Question 23

When a transformer has two primary windings, they are connected in ____________________ to operate at the lower voltage.

Question 24

A Powerstat is an autotransformer where the turns ratio can be adjusted _________________________.

Question 25

When a transformer has two primary windings, they are connected in ____________________ to operate at the highest voltage.

Question 26

Most transformer cores are made from thin steel punchings ____________________ together to form a solid core.

Question 27

The ____________________ winding of a transformer is the load winding.

Question 28

The purpose of a ____________________ conductor is to carry the difference in current between two hot conductors and maintain a balanced voltage.

Question 29

If a transformer has a primary voltage of 480 volts and a secondary voltage of 240 volts, the turns ratio of this transformer is ____________________.

Question 30

An isolation transformer that is used to change the high voltage sent out by the power company to the common 240/120 volts used to supply power to most homes and small businesses is called a(n) ____________________ transformer.

Question 31

A reactor is an inductor used to add ____________________ to the transformer circuit.

Question 32

In a(n) ____________________ transformer, there is no physical or electrical connection between the primary and secondary windings.

Question 33

A transformer that has a lower secondary voltage than primary voltage is called a ____________________ transformer.

Question 34

When computing the values of an isolation transformer with multiple secondary windings, each secondary must be treated as a different ____________________.

Question 35

A transformer where the secondary voltage is greater than the primary voltage is called a ____________________ transformer.

Question 36

The ____________________ winding of a transformer is the power input winding.

Question 37

An isolation transformer that has more than one set of lead wires connected to the primary or secondary windings is called a ____________________-tapped transformer.

Question 38

The tape wound, or toroid, core transformer is constructed by tightly winding one long continuous silicon steel tape into a ____________________.

Question 39

The core of an isolation transformer is made of steel that is laminated to reduce power losses caused by ____________________ current induction.

Question 40

A(n) ____________________ transformer is used to reduce the line voltage to the value needed to operate control circuits.

Question 41

When testing a transformer, a ____________________ will reveal insulation breakdowns that an ohmmeter will not.

Question 42

If a transformer is connected subtractive, the polarity arrows point in ____________________ directions.

Question 43

The abbreviation for kilo-volt-amps is ____________________.

Question 44

When testing a transformer for polarity, if the reading on the voltmeter indicates a voltage equal to the difference between the primary and secondary winding voltages, the windings are connected ____________________.

Question 45

If a transformer is connected additive, the polarity arrows point in the ____________________ direction.

Question 46

When the primary of a transformer is connected to power but there is no load connected to the secondary, the transformer is essentially a(n) ____________________.

Question 47

The current rating for a transformer can be determined by dividing the KVA rating by the winding ____________________.