PHEP 23 Transformers

Question 1

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

Answer 1

Completely insulated from each other

Question 2

In a transformer, the winding witch receives the energy inductively is called

Answer 2

Secondary winding

Question 3

A power transformer, trans electrical power from one circuit at a certain frequency in voltage and to a secondary circuit at

Answer 3

A different voltage and same frequency

Question 4

Transformers are classified aesthetic AC

Answer 4

True

Question 5

A transformer values 120 V secondary when a 2400 Volt source was connected across its primary assuming a primary 25 amperes the secondary current is

Answer 5

5 amps

Question 6

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

Answer 6

Step-up transformer

Question 7

Transformers having only one wing are called

Answer 7

Autotransformers

Question 8

The secondary of a potential transformer should never be

Answer 8

Connected to a load

Question 9

What is the induced secondary voltage of a transformer having a primary winding up 3000 turns in a secondary winding up 300 turns when connected to a 2400 VAC source

Answer 9

240 Volts

Question 10

In a core type transformer

Answer 10

A section of the primary and secondary wings are around each other’s legs of the core

Question 11

Current transformers are instrument transformers used to

Answer 11

Step current down

Question 12

Hysteresis can be explained as

Answer 12

Friction of the molecules due to alternating current

Question 13

When a transformer winding are connected wye

Answer 13

The line current will be the same as the phase current

Question 14

A series lighting system requires what type of transformer

Answer 14

a constant current transformer

Question 15

The rating of a transformer usually given in

Answer 15

All of the above
VA,KVA, MVA

Question 16

Bushings are used on transformers to

Answer 16

Serve as entrance into the transformer for the main leads

Question 17

The conservator system is used on transformer to

Answer 17

Preserve the dielectric strength of the transformer oil

Question 18

The secondary of a current transformer should never be

Answer 18

Open to remove the device it operates from service

Question 19

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

Answer 19

True

Question 20

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

Answer 20

Balanced condition