Final

Question 1

diodes are ___ sensitive, they conduct in one direction only.

Answer 1

polarity

Question 2

list several applications for diodes

Answer 2

any electronic device

Question 3

A _____ diode can be used as an oscillator or an amplifier.

Answer 3

tunnel

Question 4

a diode that is voltage sensitive and acts as a variable capacitor is called a _____.

Answer 4

varactor

Question 5

when a silicon diode is installed correctly it does not begin to conduct until about 0.7 volts is applied across the diode. Why?

Answer 5

Surface Barrier Voltage

Question 6

what happens if the PRV rating of a diode is exceeding?

Answer 6

destroy the diode

Question 7

diodes designed to operate at the PRV rating are called _____ diodes.

Answer 7

zener

Question 8

with a 60 hz line frequency applied to a full wave rectifier, the output ripple frequency is ____ Hz.

Answer 8

120 Hz

Question 9

define a generator

Answer 9

electromagnetic device that changes mechanical energy into electrical energy.

Question 10

what is the primary difference between a simple DC generator and a simple AC generator?

Answer 10

AC has slip rings

DC has a commutator

Question 11

AC generators operate on the principle of ____

Answer 11

electromagnetic induction

Question 12

there are two basic types of alternators. These are the revolving ____ type and the revolving ____ type

Answer 12

armature, field

Question 13

slip rings, unlike the commutator are constructed as a _____ ring, with each end of the armature loop connected to a seperate ____

Answer 13

continuous, ring

Question 14

what limits the amount of power that can be generated with the revolving armature type of generator?

Answer 14

slip rings and brushes

Question 15

when the armature is held stationery in a generator, it is called the ____.

Answer 15

stater

Question 16

what is the advantage of using a rotating field and a stationery armature on commercial generators?

Answer 16

You can hard wire it.

Question 17

two types of rotating field construction are the ___ rotor, and the ____ rotor.

Answer 17

salent pole, non salent pole

Question 18

the ____ is the rotating member of a generator or motor.

Answer 18

rotor

Question 19

exciters are made in a variety of ways including ___ and ____.

Answer 19

fixed and rotating

Question 20

pole faces that jut out and are very pronounced are called ____ poles.

Answer 20

salent

Question 21

large capacity generators are often enclosed in a _____ atmosphere for cooling purposes.

Answer 21

hydrogen

Question 22

formula for frequency of an alternator

Answer 22

of poles / 120 = FREQUENCY

Question 23

what 3 factors determine the output voltage of an alternator

Answer 23

• strength of magnetic field
• # of loops of wire
• speed of cutting action

Question 24

how do you know when the 2 alternators are in phase with each other ?

Answer 24

lights go out

Question 25

what 3 conditions must be met when connecting two, three-phase alternators in parallel?

Answer 25

- same phase rotation - A,B,C phase in same time sequence - voltage output the same

Question 26

what is the generic name for synthetic coolants?

Answer 26

askarel

Question 27

in general, once a transformer is installed , it must be ____, to qualified persons for maintenance and repair, while access is ____ to unqualified persons

Answer 27

accessible, restricted

Question 28

6 steps you can take to prevent the noise of a transformer from interfering with normal activities.

Answer 28

- select one that is quiet - install it far away from people - do not locate it in the corner of the room - mount it so that its vibration is not transmitted to the structural parts of the building - solidly mount it to the floor or concrete walls - flexible couplings between the troughs and conduits reduce noise transfer

Question 29

Ephase = Eline (Voltage) , what type of system?

Answer 29

Delta

Question 30

Iphase = Iline (Current) , what type of system?

Answer 30

Wye

Question 31

High means it is connected how?

Answer 31

in series

Question 32

Low means it is connected how?

Answer 32

in parallel

Question 33

ways to cool a transformer

Answer 33

- naturally air cooled - oil cooled - force cooled by fan - oil cooled with water jackets

Question 34

things that reduce efficiency in transformers

Answer 34

- heat loss - hystoresis - core saturation - eddy currents - flux linkage

Question 35

it is easier to transform ___ voltage

Answer 35

AC

Question 36

what is the heat formula

Answer 36

P=I2R

Question 37

most electrical power today is 3 phase power, T or F

Answer 37

true

Question 38

dc generators operate on the principle of ______

Answer 38

magnetic induction

Question 39

what happens when a conductor cuts magnetic flux line?

Answer 39

a voltage is induced

Question 40

what components make up the DC armature?

Answer 40

iron core commutator windings

Question 41

what are the three types of armature windings found in generators?

Answer 41

lap wound wave wound frogleg

Question 42

what three factors determine the level of the output voltage of a series generator?

Answer 42

strength of magnetic field number of loops of wire speed of rotation

Question 43

self excited shunt generators make use of _____ to start the generation process.

Answer 43

residual magnetism

Question 44

the greatest generation loss is due to the _____ of the armature

Answer 44

resistance

Question 45

_____ loss is due to molecular friction

Answer 45

hystoresis

Question 46

what might happen if two DC generators are simply connected in parallel?

Answer 46

they could explode

Question 47

describe the physical construction of a simple power transformer.

Answer 47

two sets of windings wrapped around a common iron core.

Question 48

a step up transformer is one which has a _____ primary voltage

Answer 48

lower

Question 49

primary bushings are marked with the letter

Answer 49

H

Question 50

secondary bushings are marked with the letter

Answer 50

X

Question 51

what is the purpose for taps on some transformers

Answer 51

taps allow for the primary voltage to be raised and lowered