Deck 13: Transformers

Question 1

Figure 13-17 Find the values specified in the following questions:
The turns ratio of the first secondary is 1:____.

A) 2.14
B) 3.55
C) 4.67
D) 5.77

Answer 1

C

Question 2

Figure 13-17 Find the values specified in the following questions:
The number of turns of wire in the first secondary winding is ____.

A) 854
B) 1005
C) 1277
D) 1401

Answer 2

D

Question 3

Figure 13-17 Find the values specified in the following questions:
The amount of primary current needed to supply the first secondary winding is ____ A.

A) 1.51
B) 2.11
C) 2.61
D) 3.01

Answer 3

C

Question 4

____ are one-winding transformers.

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

Question 5

The isolation transformer ____.

A) cannot have a turns ratio of 1:1
B) does not actually electrically isolate the primary and secondary windings
C) greatly reduces the voltage spike
D) greatly prolongs the voltage spike

Question 6

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

A) secondary
B) core
C) primary
D) mutual

Question 7

The ____ transformer changes the high voltage of power company distribution lines to the common 240/120-V used to supply power to most homes and many businesses.

A) distribution
B) HIVOLT
C) residential
D) common

Question 8

Loads that are intended to operate on 120 V, such as water heaters, electric resistance heating units, and central air conditioners, are connected directly across the lines of the secondary.

Question 9

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

A) secondary
B) primary
C) tertiary
D) core

Question 10

Assume an isolation transformer has a primary voltage of 120 V and a secondary voltage of 500 V. The turns ratio is 1:____.

A) 0.231
B) 1
C) 2.36
D) 4.17

Question 11

A good rule for any type of transformer is that power in ____.

A) is slightly greater than power out
B) is exponentially greater than power out
C) is less than power out
D) must equal power out

Question 12

Almost all nameplates will list the primary voltage, secondary voltage, and ____.

A) serial number
B) impedance
C) KVA (kilo-volt-amps) rating
D) temperature rise

Question 13

The nameplate lists the current rating of the windings.

Question 14

Transformer values of voltage, current, and turns can be computed using formulas.

Question 15

Loads that are intended to operate on 120 V connect from the center tap or ____ to one of the secondary lines.

A) positive
B) neutral
C) negative
D) primary

Question 16

When computing the values of a transformer with multiple secondary windings, treat each secondary as part of the transformer group as a whole.

Question 17

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

A) primary
B) spike
C) core
D) excitation

Question 18

Transformers are among the least efficient machines known.

Question 19

Figure 13-17 Find the values specified in the following questions:
The current flow in the first secondary is ____ A.

A) 0.49
B) 0.56
C) 0.63
D) 0.70

Question 20

A basic law concerning transformers is that all values of a transformer are proportional to its ____ ratio.

A) turns
B) induction
C) current
D) primary