Phep Transformers

Question 1

Transformers permit the transfer of electricity between two circuits, which are:

Physically connected to each other
Completely insulated from each other
Mechanically coupled to each other
Both b and c

Answer 1

Completely insulated from each other 

Question 2

And a transformer, the winding which receives the energy inductively, is called the

Primary winding
Receiving winding
Secondary winding
Equalization winding

Answer 2

Secondary winding

Question 3

A power transformer transfers electric power from one circuit at a certain frequency and voltage, and to a second circuit at:

A higher voltage and frequency
A lower voltage and frequency
A different voltage and same frequency
A different voltage and frequency

Answer 3

A different voltage and same frequency

Question 4

Transformers are classed as static AC machines

True
False

Answer 4

True 

Question 5

A transformer developed 120 V in its secondary winding a 2400 V source was connected across its primary. Assuming a primary current of .25 amperes the secondary circuit is

5 A
40 A
250 A
100 A

Answer 5

5A

Question 6

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

Step down transformer
High side transformer
Low side, transformer
Step up transformer 

Answer 6

Step up transformer

Question 7

Transformers having only one winding are called

Potential transformers
Current transformers
Constant current transformers
Autotransformers

Answer 7

Autotransformers 

Question 8

The secondary of a potential transformer should never be

Connected to a load
Short circuited to remove the device it operates from service
Grounded to remove the device and operates from service
Connected using copper wires

Answer 8

Short circuited to remove the device and operates from service

Question 9

What is the induced secondary voltage of a transformer having a primary winding of 3000 turns and a secondary winding of 300 turns when connected to a 2400 V AC source?

7,200,000 V
24,000 V
240 V
720 V

Answer 9

240 V

Question 10

In a core type transformer

A section of the primary and secondary windings are wound around each leg of the core
The core forms, a shell completely surrounding the windings
The windings completely surround the core
None of the above 

Answer 10

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

Question 11

Current transformers are instrument transformers used to

Step current down
Step voltage down
Step current up
Both A and B 

Answer 11

Step current down


Question 12

Hysteresis can be explained as

Circulating electrical currents
Resistance of the windings
Heating of the insulation due to overvoltage
Friction of the molecules due to alternating current 

Answer 12

Friction of the molecules due to alternating current

Question 13

When a transformers windings are connected wye:

The line current will be greater than the phase current
The line current will be the same as the phase current
The line voltage will be the same as the phase voltage
The line current will be lower than the phase current 

Answer 13

The line current will be the same as the phase current

Question 14

A series street lighting system requires what type of transformer?

And auto transformer
A constant current transformer
A series transformer
None of the above

Answer 14

A constant current transformer 

Question 15

The rating of a transformer is usually given in:
VA volt amperes
KVA kilovolt amperes
MVA Megavolt amperes
All of the above

Answer 15

All of the above

Question 16

Bushings are used on transformers to

Serve as secondary transformer, windings
Serve as primary transformer windings
Serve as sudden pressure protective devices
Serve as entrances into the transformer for the main leads

Answer 16

Serve as entrances into the transformer for the main leads

Question 17

The conservator system is used on a transformer to:

 Preserve the dielectric strength of the transformer oil
Conserve power lost through heat
Preserve the temperature of the oil during the winter
Conserve the amount of transformer oil

Answer 17

Preserve the dielectric strength of the transformer oil

Question 18

The secondary of a current transformer should never be

Short-circuited to remove the device that operates from service
Connected to a load
Opened to remove the device it operates from service
All of the above 

Answer 18

Opened to remove the device it operates from service

Question 19

In an energized transformer iron losses are present, even if there is no load on the secondary

True
False

Answer 19

True 

Question 20

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

Winding
Balanced condition
Space filled with oil that has low, dielectric strength
All of the above

Answer 20

Balanced condition