Transformers III

Question 1

A(n) ? is an explosion that occurs when the surrounding air becomes ionized and conductive.
Select one:

a.
arc blast

b.
ground fault

c.
main bonding jumper

d.
voltage spike

Answer 1

A

Question 2

A(n) ? is a short circuit through air.
Select one:

a.
arc blast

b.
arc flash

c.
voltage spike

d.
voltage surge

Answer 2

B

Question 3

? specifically addresses “electrical safety requirements for employee workplaces that are necessary for the safeguarding of employees in their pursuit of gainful employment”.
Select one:

a.
ANSI Z535.4

b.
IEEE Standard 1584-2002

c.
NFPA 70E

d.
OSHA Part 1910.333

Answer 3

C

Question 4

The Occupational Safety and Health Administration is a federal agency that requires all employers to provide a safe environment for their employees.
Select one:
True
False

Answer 4

True

Question 5

A control transformer should never be protected on both the primary and the secondary.
Select one:
True
False

Answer 5

True

Question 6

A(n) ? is a method of wiring transformers where the windings are divided over several legs of transformer core.
Select one:

a.
double-delta connection

b.
interconnected wye connection

c.
T-connection

d.
zigzag connection

Answer 6

D

Question 7

A ? is two or more transformers wired in parallel that carry a common load.
Select one:

a.
double-delta connection

b.
parallel connection

c.
Scott connection

d.
T-connection

Answer 7

B

Question 8

A(n) ? is a low-cost method of wiring two transformers to provide 3-phase power.
Select one:

a.
double-delta connection

b.
interconnected wye connection

c.
Scott connection

d.
T-connection

Answer 8

D

Question 9

A ? is a power supply consisting of two phases that are 90° out-of-phase.
Select one:

a.
2-phase system

b.
double-delta connection

c.
Scott connection

d.
Scott system

Answer 9

A

Question 10

A 3-phase to 3-phase transformer connection without taps can be divided into one of three groups with angular displacements of ? .
Select one:

a.
0°, 30°, or 90°

b.
0°, 30°, or 180°

c.
30°, 60°, or 90°

d.
30°, 60°, or 180°

Answer 10

B

Question 11

Which of the following is not a consideration involved in selecting an appropriate transformer?
Select one:

a.
The permitted noise level

b.
The present and future loads

c.
The required and available cooling and ventilation

d.
The requirements for the primary and secondary voltages

e.
The time required to install the transformer

Answer 11

E

Note: There are additional considerations:

1. A two-winding transformer, autotransformer, or buck-boost transformer
2. Single-phase or 3-phase
3. To be used for step up, step down, or isolation

Question 12

What is the full load primary current of a 3-phase 15-kilovolt-ampere dry-type transformer at 480 volts?

Answer 12

18 A

(KVA X 1000)/(V X 1.73)

(15 X 1000)/(480 X 1.73) = 18A

Question 13

What is the full load secondary current of a 3-phase 75-kilovolt-ampere dry-type transformer at 600 volts?

Answer 13

72A

(KVA X 1000)/(V X 1.73)

(75 X 1000)/(600 X 1.73 = 72A

Question 14

The ? is the ratio of the 10-minute reading to the 1-minute reading taken on a dielectric absorption test.
Select one:

a.
dissipation factor

b.
insulation power factor

c.
polarization index

d.
turns ratio

Answer 14

C

Question 15

Insulating mineral oil is lighter than water.
Select one:
True
False

Answer 15

True

Question 16

A ? disc typically consists of a thin layer of metal mounted in a disc holder.
Select one:

a.
pressure

b.
relief

c.
rupture

d.
vent

Answer 16

C

Question 17

? current is caused by the polarization of molecules within the dielectric material.
Select one:

a.
Capacitive absorption

b.
Capacitive leakage

c.
Conductive leakage

d.
Polarization absorption

Answer 17

D

Question 18

? is the ratio of the power dissipated in the insulation in watts, to the apparent power in volt-amperes.
Select one:

a.
Dielectric index

b.
Insulation power factor

c.
Polarization index

d.
Turns ratio

Answer 18

B