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ELEC 279 > MOD 3-4 > Flashcards

MOD 3-4 Flashcards

1
Q

What is a capacitor?

A

a device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator

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2
Q

What other device stores electric charge that you can buy at any store?

A

Battery

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3
Q

In relation to electronics what is Tau?

A

Time constant

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4
Q

To get the total capacitance you ___ capacitor values when wired in Parallel, and use the formula get the total capacitance when wired in series.

A

ADD C total ______1__________

_1_ + _1_ + _1_

C1 C2 C3

get the total capacitance when wired in series.

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5
Q

What makes capacitors dangerous?

A

They store a charge, that can be present even when power to a circuit is turned off

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6
Q

Capacitors Block____ and PASS ____

A

DC - AC

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7
Q

Capacitors resist a change in voltage while inductors resist a change in

A

Current

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8
Q

When electricity flows through a wire it creates a ______ field, when you move a wire through a ______ field it creates _______

A

Magnetic- Magnetic - Electricity

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9
Q

Capacitors are measured in _____ Inductors are measured in _______

A

farads and henrys

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10
Q

What is the formula for Tau in an inductive circuit?

A

T=L/R

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11
Q

What is the formula for capacitive reactance?______, this means that as the frequency increases the capacitive reactance will ________.

A

Xc=1/2πfC - DECREASE

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12
Q

What is the formula for inductive reactance? _______, this means that as the frequency increases the inductive reactance will ________.

A

XL=2πfL, INCREASE

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13
Q

What is the lowest frequency you can get? ____HZ, or DC. If I plug this in to the above equation’s XC will equal _______ and XL will equal ___. So for DC a capacitor looks like a _____, and an inductor looks like a short (just a piece of wire).

A

0 HZ - INFINITE 0HZ - OPEN

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14
Q

Reactance is?

A

Is a form of opposition like resistance in an AC circuit made up of Xc, XL and resistance to form an overall impedance, or total opposition in an AC circuit.

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15
Q

The Inductance is ________ proportional to the length of the coil at a constant number of turns.

A

inversely

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16
Q

ELI stand for?

A

The Voltage “E” leads the current “I” in an inductor “L”

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17
Q

ICE stands for?

A

Current “I” in a capacitor “C” leads the voltage “E”

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18
Q

How do capacitors store energy?

A

Capacitors store energy in the form of electrostatic fields

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19
Q

Voltage lead current in a ______ circuit.

A

Inductive

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20
Q

Z or impedance is the vector sum of

A

Capacitance reactance Xc, Inductive reactance XL, and resistance R.

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21
Q

Resonance is when XC and XL

A

Equal

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22
Q

Transformer can only be used in a_______ circuit, because a coil of wire is really just a short to DC voltages.

A

AC

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23
Q

IF the primary side of a transformer (the side I’m putting AC voltage in to) has 2 turns and the secondary side (the side I’m taking voltage out of) has 4 turns, and I put 1 volt AC on the primary I will get ___ Volts AC on the secondary

A

2

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24
Q

The AC voltage coming out of a plug in the wall is 120VRMS, my phone only needs 5 VDC to charge, so I could use a transformer with a ____: ____, turns ratio to step down the 120 volt to 5 volts so my phone does not blow up when I plug my charger into the wall

A

24:1

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25
Q

True, actual, or real AC power is measured in_____, and is the Beer in the glass (A2).

A

Watts

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26
Q

Reactive power is measured in ____, and is the foam in the class of beer (B2)

A

VAR

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27
Q

Apparent power is measured in __, and is the “C2 “, in the good old formula A2+B2=C2

A

VA

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28
Q

Power factor is the ratio of _________ power and apparent power. In a purely resistive circuit the power factor would be ___, meaning 100% of the power would be doing work.

A

TRUE or REAL , 1

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29
Q

In the diagram I’m paying for VL, but only using Vr to do actual or real work. Going back to what we have learned about impedance, what could I install on all my motors, so to the power company it looks like I only have a resistive load, and only pay for Vr saving my company a ton of money?

A

BIg Capacitors

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30
Q

If I move a conductor in relation to a magnet I make

A

Electricity

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31
Q

A coil of wire becomes a ______ when I run electricity through it

A

magnet

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32
Q

he more current I pass through the coils of my electro magnet the greater the magnetic ______becomes.

A

Field

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33
Q

The stronger the magnet field is that I pass my conductor through, the more _______________________________ will be induced in my Conductor

A

CURREN/VOLTAGE/ELECTRICITY

34
Q

If I rotate my conductor at the same speed through my electromagnet, and I want to increase or decrease the amount of electricity (Voltage) in the conductor, all I would have to do is increase or decrease the voltage to my ___________________.

A

ELECTROMAGNET/FIELD.

35
Q

To make electricity I can either rotate the _______ in relation to the _______ or rotate the _______ in relation to the ______

A

MAGNET- CONDUCTOR-CONDUCTOR-MAGNET

36
Q

In AC generation the conductor portion that has electricity induced into it by the magnet FIELD is called .

A

armature

37
Q

Magnet have a ______ and _____ POLE.

A

NORTH -SOUTH

38
Q

Changing how fast I rotate the magnetic FIELD in relation to my conductor (armature), will change the ___________ of the AC voltage I get out.

A

FREQUENCY

39
Q

The formula for the frequency of an AC alternator/generator is _______, where P=number of magnetic poles (always even), N=The speed of rotation in RPM, and the 120 is just the conversion from Minutes to seconds (RPM is in minutes frequency is in seconds or / by 60) and from poles to pairs of poles (always use 2, thus 60 X 2=120)

A

f=PN/120

40
Q

So if I wanted to change the frequency of the AC voltage coming off the armature of an AC generator I could change the ________ of rotation or the number of _____ I build into my generator

A

SPEED/RPM- POLES

41
Q

I go buy a generator from the store and now I am forever going to be stuck with the number of poles that it came with, the only way I can change the frequency now is to change _______

A

SPEED/RPM

42
Q

I now have a problem, I need my generator/alternator to always output 400Hz (so a fixed speed), and my engine speed (RPM) that it is hook up to changes all the time, I solve this by using a

A

CONSTANT SPEED DRIVE/CSD

43
Q

To clear some stuff up what is the difference between an Alternator and a Generator?

A

The alternator converts mechanical energy into AC while a generator converts it into both AC and DC.

Alternators have a rotating magnetic field, and a generator has a stationary magnetic field.

Alternators receive energy supply from the stator, and generators receive that supply from the rotor.

44
Q

If we combine the Generator and CSD into one unit we call it a

A

INTERGRATED DRIVE GENERATOR.

45
Q

In a “Generator” I rotate the armature (the conductor I’m inducing the voltage into), and I need to supply this induced voltage to my loads that draw 100’s of amps, I do this using _______ that provide the mechanical connection to the spinning armature through the Commutator.

A

BRUSHES

46
Q

If I stick my shoe on the pavement while driving down the road (shoe=brush, pavement=commutator) it is going to ________, and I’m going to want check this wear often to make sure I always have some shoe/brush left

A

WEAR OUT

47
Q

We need the electricity we are making with the generator to have a fixed frequency and a fixed voltage (115V and 400Hz), with very tight tolerances, so we don’t blow up all the very expensive Avionics equipment on an aircraft. We control the frequency using a ______, and we can control the voltage by varying the ___________ of the magnet field, by changing the voltage to it.

A

CSD- STRENGTH

48
Q

When the voltage from my generator drops due to an increase in load, I will have to______ the voltage to the magnetic _____________ to compensate, and ______ the voltage to the field when the load decreases, in order to keep the output volt constant, we call this ___________________.

A

INCREASE- FIELD (MAKE IT STRONGER)-DECREASE-

VOLTAGE REGULATION

49
Q

When we put all the thing we want to control and monitor in the alternator/generator system (Voltage regulation, overcurrent protection, overvoltage protection, frequency and phase monitoring) into one box, we call it a ______________ or ____ for short.

A

GENERATOR CONTROL UNIT

50
Q

AC motors are just like AC Generators, except for a generator I put mechanical energy in and get AC power out and a MOTOR I put _______ in and get _________

A

AC power-Mechanical energy out.

51
Q

The 3 main types of AC motor are?

A

Universal, Induction and synchronous.

52
Q

The type of motor most commonly found on aircraft is the _______

A

Induction

53
Q

A Universal Motor is called that because it can be driven with both ________, you can tell the motor you are looking is a universal one because it has _____.

A

AC and DC-Brushes

54
Q

You install a 3 phase motor, and when you go to test it, it runs backwards, what is the most probable cause ___________________(done at the overhaul facility of course)

A

Two phases are swapped

55
Q

All AC motor have data plates, where we can find all sorts of information, the most important thing to look at right off the bat would be what ________it needs to run, and what ________ that voltage is. Because if I hook a 115V/60Hz motor up to 208V at 400Hz I would let all the smoke out.

A

Voltage- Frequency

56
Q

The two main parts of an Induction motor are the ______ and the _____.

A

stator -rotor

57
Q

Single phase induction motors are inherently hard to get up and running, two ways we overcome this are to use __________ or ________

A

Shaded poles - Capacitor start

58
Q

With a Generator we were concerned with what frequency it produced for a give speed we drive it at, and use the equation ______. But with a motor it would be nice to know how fast it’s going to turns or “N” (RPM), so we just rearrange it to solve for N and get______, where P=_______, f=_______, and N = RPM.

A

f=PN/120

  • N=120f/P

Number of poles

Frequency

59
Q

Some advantages of AC motors are?

A

More power to weight

Easier to build, less expensive

Some don’t need brushes, less wear and tear, last longer with less maintenance

60
Q

capacitor look like ______to DC voltage

A

OPEN

61
Q

the inductance current will flow in the opposite direction (Lenz Law ) and is called __________for that reason

A

counter EMF

62
Q

capacitance in series when the dialectric thikness increases the circuit is less ________

A

capacitance

63
Q

capacitance in parallel when the plate area increases the capacitance _______

A

Increases

64
Q

Inductance is proportional to the numbers of _____

A

turns squared

65
Q

Inductances varies in direct proportion to the ________

A

Cross-sectional area

66
Q

inductance varies in inverse proportion to the lenght of the coil at constant ______

A

number of turns

67
Q

inductor oppose the change on ______and capacitor oppose the change on in ______

A

current-voltage

68
Q

inductors are _________devices and capacitors are ________devices

A

electromagnetic - electrostatic

69
Q

t (tau) fro an inductance circuit is______ and t(tau) for capacitance is _____

A

L/R

R X C

70
Q

Why we used trasformers ?

A

less amperage to be able to run light wire

71
Q

power factor formula

A

true power/ apparent power

72
Q

criteria of a good solder

A

shiny, smoth, good penetracion, no excess solder

73
Q

the magnetic field can be stationary and voltage induce into roatring armature is generally consider a

A

generator

74
Q

the magnetic field can be rotated and the voltage is induce into a stacionary coil (winding) is consider as an ?

A

alternator

75
Q

advantages of AC motors

A
  • constant speed
  • Easer to buidl, less expensive
  • more power lees weight

less MTC

76
Q

the direction of the rotation in a 3-phase induction motor can be change by ?

A

interchanging any two stators winding connections

77
Q

the synhronous rotation speed (RPM) of an AC motor can be determined by this formula

A

N=120f / P

f= frecuency

P=number of poles

78
Q

difference between actual speed and sychronous speed is called

A

SLIP

79
Q

3 phase inductor motor does not required any additional _______devices

A

starting

80
Q

two method of starting a sigle phase induction motor

A
  • shaded poles
  • capacitor start
81
Q
A

ELEC 279 (4 decks)

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