A

Question 1

Current rating formula

Answer 1

VA ÷ V

Question 2

KVA (apparent power) formula

Answer 2

V X A ÷ 1000

Question 3

Watts in a transformer formula

Answer 3

VA X PF

Question 4

Volts per turn of wire formula

Answer 4

V/turn = V ÷N

Question 5

Actual primary voltage % tap formula

Answer 5

Actual primary voltage - rated primary voltage ÷ rated primary voltage

Question 6

KVA (apparent power) formula

Answer 6

KVA = V X A ÷ 1000

Question 7

Watts formula

Answer 7

VA X pf

Question 8

Taps - actual prime voltage formula

Answer 8

Actual prime voltage - rate prime voltage ÷ rated prime voltage

Question 9

Number of turns formula

Answer 9

V ÷ V / per turn

Question 10

Each winding lead that is marked with an even number

Answer 10

Should have the same polarity

Question 11

The relative direction of the transformer prime voltage compared to the direction of its induced secondary voltage

Answer 11

Transformer polarity

Question 12

If a transformer is constructed so terminal X1 is diaganal from terminal H1

Answer 12

Additive polarity transformer

Question 13

Transformer constructed so X1 is directly opposite H1

Answer 13

Subtractive polarity transformer

Question 14

Ways taps can be changed

Answer 14

• manually changing the leads
• moving connecting bars
• installing a mechanical device

Question 15

5% Full capacity below normal (FCBN)

Answer 15

Used when primary supply voltage is 5% lower than rated voltage

Question 16

5% Full capacity above normal (FCAN)

Answer 16

Supply voltage is 5% higher than rated voltage

Question 17

Taps
2.5% reduced capacity below normal RCBN

Answer 17

Supply voltage is 2.5% lower than rated voltage

Question 18

Additive or subtractive.
Same polarity =

Answer 18

Subtractive

Question 19

Different polarities

Are they additive or subtractive?

Answer 19

Additive

Question 20

Explain secondary winding taps

Answer 20

Transformers have taps arranged in the primary (high voltage) winding so that the proper secondary voltage is obtained

Question 21

The process where an EMF is produced in a conductor from the interaction of the conductor and magnetic field is called

Answer 21

Induction

Question 22

The property of a coil that apposes a change in current is called

Answer 22

Inductance

Question 23

When a change of current in one curcuit causes a voltage to be induced into another circuit it is called?

Answer 23

Mutual induction. Also called transformer action

Question 24

A basic mutual induction transformer has at least how many coils

Answer 24

2

Question 25

The opposition offered to the establishment of magnetic flux in a circuit is called

Answer 25

Reluctance. Air has high reluctance Iron has low

Question 26

Eddie currents are produced by

Answer 26

Heat

Question 27

Two types of core losses are

Answer 27

Eddie current and hysteresis

Question 28

What do transformer name plates list

Answer 28

Primary voltage Secondary voltage KVA rating

Question 29

Name a transformers 3 functions

Answer 29

Step up voltage Step down voltage Isolate one curcuit from another

Question 30

What isolates the conductors on the output side from the ground

Answer 30

Isolation transformer

Question 31

What test is performed to get impedence

Answer 31

Short circuit test

Question 32

Opposition to a change of current in a coil is?

Answer 32

Inductance

Question 33

A change in current in one curcuit causes a voltage to be induced in another is called?

Answer 33

Mutual induction

Question 34

A change in current in a circuit induces a voltage into itself

Answer 34

Self induction

Question 35

Name 3 construction types of transformers

Answer 35

Core type Shell type H type They have 95% - 98% efficiency

Question 36

Copper losses are measured with what test?

Answer 36

Short circuit test