MOD 3-4 Flashcards
What is a capacitor?
a device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator
What other device stores electric charge that you can buy at any store?
Battery
In relation to electronics what is Tau?
Time constant
To get the total capacitance you ___ capacitor values when wired in Parallel, and use the formula get the total capacitance when wired in series.
ADD C total ______1__________
_1_ + _1_ + _1_
C1 C2 C3
get the total capacitance when wired in series.
What makes capacitors dangerous?
They store a charge, that can be present even when power to a circuit is turned off
Capacitors Block____ and PASS ____
DC - AC
Capacitors resist a change in voltage while inductors resist a change in
Current
When electricity flows through a wire it creates a ______ field, when you move a wire through a ______ field it creates _______
Magnetic- Magnetic - Electricity
Capacitors are measured in _____ Inductors are measured in _______
farads and henrys
What is the formula for Tau in an inductive circuit?
T=L/R
What is the formula for capacitive reactance?______, this means that as the frequency increases the capacitive reactance will ________.
Xc=1/2πfC - DECREASE
What is the formula for inductive reactance? _______, this means that as the frequency increases the inductive reactance will ________.
XL=2πfL, INCREASE
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).
0 HZ - INFINITE 0HZ - OPEN
Reactance is?
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.
The Inductance is ________ proportional to the length of the coil at a constant number of turns.
inversely
ELI stand for?
The Voltage “E” leads the current “I” in an inductor “L”
ICE stands for?
Current “I” in a capacitor “C” leads the voltage “E”
How do capacitors store energy?
Capacitors store energy in the form of electrostatic fields
Voltage lead current in a ______ circuit.
Inductive
Z or impedance is the vector sum of
Capacitance reactance Xc, Inductive reactance XL, and resistance R.
Resonance is when XC and XL
Equal
Transformer can only be used in a_______ circuit, because a coil of wire is really just a short to DC voltages.
AC
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
2
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
24:1
True, actual, or real AC power is measured in_____, and is the Beer in the glass (A2).
Watts
Reactive power is measured in ____, and is the foam in the class of beer (B2)
VAR
Apparent power is measured in __, and is the “C2 “, in the good old formula A2+B2=C2
VA
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.
TRUE or REAL , 1
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?
BIg Capacitors
If I move a conductor in relation to a magnet I make
Electricity
A coil of wire becomes a ______ when I run electricity through it
magnet
he more current I pass through the coils of my electro magnet the greater the magnetic ______becomes.
Field
The stronger the magnet field is that I pass my conductor through, the more _______________________________ will be induced in my Conductor
CURREN/VOLTAGE/ELECTRICITY
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 ___________________.
ELECTROMAGNET/FIELD.
To make electricity I can either rotate the _______ in relation to the _______ or rotate the _______ in relation to the ______
MAGNET- CONDUCTOR-CONDUCTOR-MAGNET
In AC generation the conductor portion that has electricity induced into it by the magnet FIELD is called .
armature
Magnet have a ______ and _____ POLE.
NORTH -SOUTH
Changing how fast I rotate the magnetic FIELD in relation to my conductor (armature), will change the ___________ of the AC voltage I get out.
FREQUENCY
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)
f=PN/120
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
SPEED/RPM- POLES
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 _______
SPEED/RPM
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
CONSTANT SPEED DRIVE/CSD
To clear some stuff up what is the difference between an Alternator and a Generator?
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.
If we combine the Generator and CSD into one unit we call it a
INTERGRATED DRIVE GENERATOR.
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.
BRUSHES
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
WEAR OUT
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.
CSD- STRENGTH
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 ___________________.
INCREASE- FIELD (MAKE IT STRONGER)-DECREASE-
VOLTAGE REGULATION
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.
GENERATOR CONTROL UNIT
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 _________
AC power-Mechanical energy out.
The 3 main types of AC motor are?
Universal, Induction and synchronous.
The type of motor most commonly found on aircraft is the _______
Induction
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 _____.
AC and DC-Brushes
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)
Two phases are swapped
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.
Voltage- Frequency
The two main parts of an Induction motor are the ______ and the _____.
stator -rotor
Single phase induction motors are inherently hard to get up and running, two ways we overcome this are to use __________ or ________
Shaded poles - Capacitor start
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.
f=PN/120
- N=120f/P
Number of poles
Frequency
Some advantages of AC motors are?
More power to weight
Easier to build, less expensive
Some don’t need brushes, less wear and tear, last longer with less maintenance
capacitor look like ______to DC voltage
OPEN
the inductance current will flow in the opposite direction (Lenz Law ) and is called __________for that reason
counter EMF
capacitance in series when the dialectric thikness increases the circuit is less ________
capacitance
capacitance in parallel when the plate area increases the capacitance _______
Increases
Inductance is proportional to the numbers of _____
turns squared
Inductances varies in direct proportion to the ________
Cross-sectional area
inductance varies in inverse proportion to the lenght of the coil at constant ______
number of turns
inductor oppose the change on ______and capacitor oppose the change on in ______
current-voltage
inductors are _________devices and capacitors are ________devices
electromagnetic - electrostatic
t (tau) fro an inductance circuit is______ and t(tau) for capacitance is _____
L/R
R X C
Why we used trasformers ?
less amperage to be able to run light wire
power factor formula
true power/ apparent power
criteria of a good solder
shiny, smoth, good penetracion, no excess solder
the magnetic field can be stationary and voltage induce into roatring armature is generally consider a
generator
the magnetic field can be rotated and the voltage is induce into a stacionary coil (winding) is consider as an ?
alternator
advantages of AC motors
- constant speed
- Easer to buidl, less expensive
- more power lees weight
less MTC
the direction of the rotation in a 3-phase induction motor can be change by ?
interchanging any two stators winding connections
the synhronous rotation speed (RPM) of an AC motor can be determined by this formula
N=120f / P
f= frecuency
P=number of poles
difference between actual speed and sychronous speed is called
SLIP
3 phase inductor motor does not required any additional _______devices
starting
two method of starting a sigle phase induction motor
- shaded poles
- capacitor start
