Transformers

Question 1

what are transformers responsible for?

Answer 1

the production and control of high voltage - regulation and current

Question 2

electromagnetic device that changes low voltage to high voltage or high voltage to low voltage without altering power in system

Answer 2

transformers

Question 3

what principle do transformers work off of

Answer 3

electromagnetic mutual induction

Question 4

which type of current do transformers need

Answer 4

alternating current

Question 5

what does a simple transformer consist of

Answer 5

2 highly insulated coils lying side by side, a primary and secondary coil

Question 6

explain simple transformer principle

Answer 6

primary coil supplied with AC, magnetic field that varies in direction and strength is set around the coil, changing magnetic flux cuts across the turns of the secondary coil which induces AC in secondary coil by mutual induction

Question 7

transformer law

Answer 7

the EMF induced in the secondary coil is directly related to the amount of turns when compared to the primary coil

Question 8

as the number of turns in the secondary coil increases,

Answer 8

the induced EMF increases

Question 9

as the number of turns in the secondary coil decreases,

Answer 9

the EMF produced decreases

Question 10

formula for transformer law

Answer 10

Vp / Vs = Np / Ns (V is voltage and N is number of turns)

Question 11

step-up transformer

Answer 11

has more secondary windings, steps up voltage

Question 12

step-down transformer

Answer 12

has less secondary windings, steps down voltage

Question 13

if voltage increases in a transformer, what happens to current?

Answer 13

current decreases in order to maintain power in the system (P = V x I)

Question 14

describe air core transformer

Answer 14

2 coils lying side by side, weak, loss of magnetic flux

Question 15

loss of magnetic field at the ends of cores in transformers

Answer 15

Flux leakage

Question 16

describe open core transformer

Answer 16

iron core within coils, more efficient than air core, intensifies magnetic flux, has flux leakage at ends of cores

Question 17

describe closed core transformer

Answer 17

heavy insulated coils, continuous path for magnetic flux, donut shaped iron core with windings around core

Question 18

describe core in closed core transformer

Answer 18

laminated silicon steel to reduce Eddy currents or loss of current

Question 19

Eddy currents

Answer 19

loss of current due to the swirling effect of changing current and the changing of magnetic fields within the system

Question 20

which type of transformer is most efficient?

Answer 20

shell type transformer

Question 21

what is a shell type transformer made of

Answer 21

laminated silicon steel shell

Question 22

describe construction of shell type transformer

Answer 22

primary windings are wrapped around secondary windings around a central core

Question 23

formula for efficiency

Answer 23

E% = (power output / power input) x 100

Question 24

efficiency is equal to

Answer 24

the ratio of power input to the power output

Question 25

3 types of losses of power

Answer 25

copper losses, eddy currents, hysteresis loss

Question 26

electrical resistance due to material and size of conductor

Answer 26

copper losses

Question 27

which power loss produces heat in the core, causing heat loss

Answer 27

eddy currents and hysteresis loss

Question 28

power loss due to the ever changing direction of magnetic domains in the iron core

Answer 28

hysteresis loss

Question 29

other names for autotransformer

Answer 29

kV selector or variable transformer

Question 30

varies input voltage to primary side of the fixed ratio transformer

Answer 30

variable transformer

Question 31

a solenoid with an iron core is called a

Answer 31

electromagnet

Question 32

what are taps?

Answer 32

where the insulation is bare at regular intervals along the coil

Question 33

construction of an auto-transformer

Answer 33

single insulated coil wrapped around iron core with openings in the insulation called taps

Question 34

each tap in an auto-transformer contains

Answer 34

a value of voltage

Question 35

variable resistor, allows the changing of voltage by varying resistance and keeping current constant

Answer 35

Rheostat

Question 36

choke coil

Answer 36

electromagnetic device that works on self induction, magnetic flux is changed inducing EMF changes

Question 37

current is ____ related to the number of turns

Answer 37

inversely

Question 38

full transformer law formula

Answer 38

Vp / Vs = Np / Ns = Is / Ip

Question 39

alternate regulators for filament circuit

Answer 39

choke coil , rheostat, saturable reactor

Question 40

alternate regulators for voltage circuit

Answer 40

choke coil, rheostat, autotransformer

Question 41

a special form of inductor where the magnetic core can be deliberately saturated by means of DC current flowing in a control winding

Answer 41

saturable reactor

Question 42

what happens once a saturable reactor is saturated with DC

Answer 42

the inductance of the saturable reactor drops dramatically therefore decreasing current