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Question 1

Transformers permit the transfer of electric energy between two circuits which are

Answer 1

Completely insulated from each other

Question 2

The winding which receives the energy inductively is called the

Answer 2

Secondary winding

Question 3

The power transformer transfers electric power from one circuit–at a certain frequency and voltage– to a second circuit at

Answer 3

The same frequency and a different voltage

Question 4

Transformers are classed as static AC machines (T or F)

Answer 4

True

Question 5

A transformer developed 120volts in it’s secondary when a 2400 volt source was connected across its primary. Assuming a primary current of .25amps, the secondary current is:

Answer 5

5 amps

E1 x I1= E2 x I2

2400 x .25= 120 x I2

Question 6

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

Answer 6

Step-up transformer

Question 7

Transformers having only one winding are called

Answer 7

Auto-transformers

Question 8

The secondary terminals should never be __________ (on a potential transformer)

Answer 8

Short-circuited

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 VAC source?

Answer 9

240 volts

E1 T1
—- = —–
E2 T2

Question 10

In a core-type transformer:

Answer 10

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

Question 11

Current transformers are used to:

Answer 11

Step current down

Think CTs

Question 12

Hysteresis can be explained as:

Answer 12

Friction of the molecules due to alternating current

Question 13

When transformer windings are connected wye

Answer 13

Line current will be the same as phase current

Question 14

Series street lighting systems require

Answer 14

Constant current supplied by a transformer

Question 15

The rating of transformer is usually given in

Answer 15

All of the above

Volt-amps va, kva, mva

Question 16

Bushings used on transformers serve as

Answer 16

Entrances into the transformers for the main leads

Question 17

The conservator system is used on transformers to:

Answer 17

Preserve the dielectric strength of the transformer oil

Question 18

The secondary of a current transformer should never be:

Answer 18

Opened

Question 19

Iron losses occur in a transformer whenever the primary is energized even though no load is on the secondary winding. T or F

Answer 19

True

Question 20

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

Answer 20

Balanced condition