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ETI 2nd Year > Final > Flashcards

Final Flashcards

1
Q

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

A

polarity

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2
Q

list several applications for diodes

A

any electronic device

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3
Q

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

A

tunnel

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4
Q

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

A

varactor

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5
Q

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

A

Surface Barrier Voltage

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6
Q

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

A

destroy the diode

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7
Q

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

A

zener

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8
Q

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

A

120 Hz

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9
Q

define a generator

A

electromagnetic device that changes mechanical energy into electrical energy.

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10
Q

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

A

AC has slip rings

DC has a commutator

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11
Q

AC generators operate on the principle of ____

A

electromagnetic induction

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12
Q

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

A

armature, field

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13
Q

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

A

continuous, ring

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14
Q

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

A

slip rings and brushes

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15
Q

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

A

stater

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16
Q

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

A

You can hard wire it.

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17
Q

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

A

salent pole, non salent pole

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18
Q

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

A

rotor

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19
Q

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

A

fixed and rotating

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20
Q

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

A

salent

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21
Q

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

A

hydrogen

22
Q

formula for frequency of an alternator

A

of poles / 120 = FREQUENCY

23
Q

what 3 factors determine the output voltage of an alternator

A
  • strength of magnetic field
  • # of loops of wire
  • speed of cutting action
24
Q

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

A

lights go out

25
Q

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

A
  • same phase rotation
  • A,B,C phase in same time sequence
  • voltage output the same
26
Q

what is the generic name for synthetic coolants?

A

askarel

27
Q

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

A

accessible, restricted

28
Q

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

A
  • 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
29
Q

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

A

Delta

30
Q

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

A

Wye

31
Q

High means it is connected how?

A

in series

32
Q

Low means it is connected how?

A

in parallel

33
Q

ways to cool a transformer

A
  • naturally air cooled
  • oil cooled
  • force cooled by fan
  • oil cooled with water jackets
34
Q

things that reduce efficiency in transformers

A
  • heat loss
  • hystoresis
  • core saturation
  • eddy currents
  • flux linkage
35
Q

it is easier to transform ___ voltage

A

AC

36
Q

what is the heat formula

A

P=I2R

37
Q

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

A

true

38
Q

dc generators operate on the principle of ______

A

magnetic induction

39
Q

what happens when a conductor cuts magnetic flux line?

A

a voltage is induced

40
Q

what components make up the DC armature?

A

iron core
commutator
windings

41
Q

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

A

lap wound
wave wound
frogleg

42
Q

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

A

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

43
Q

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

A

residual magnetism

44
Q

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

A

resistance

45
Q

_____ loss is due to molecular friction

A

hystoresis

46
Q

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

A

they could explode

47
Q

describe the physical construction of a simple power transformer.

A

two sets of windings wrapped around a common iron core.

48
Q

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

A

lower

49
Q

primary bushings are marked with the letter

A

H

50
Q

secondary bushings are marked with the letter

A

X

51
Q

what is the purpose for taps on some transformers

A

taps allow for the primary voltage to be raised and lowered

ETI 2nd Year (1 decks)

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