AEIS CHAPTER 1 Flashcards by crash theporsche

What is the Formula for EMF

e = Blvsinθ

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e in e = Blvsinθ represents

emf

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B in e = Blvsinθ represents

flux intensity

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l in e = Blvsinθ represents

conductor length

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v in e = Blvsinθ represents

speed of conductor cutting the flux lines

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θ in e = Blvsinθ represents

relative angle between conductor and flux lines

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What is the Formula for frequency

f = NP/120

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N in f = NP/120 represents

conductor rotation speed in rpm

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P in f = NP/120 represents

number of poles in machine

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What is a CSD/CSU

Constant Speed Drive/Unit

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What is the purpose of a CSD/CSU?

to ensure alternator will produce a constant output frequency and voltage regardless of engine speed

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IDG =

Integrated Drive Generator

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IDG consists of

CSD + Generator mounted side by side into one compact unit

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what is normal practice to combat the large amount of heat produced by an IDG

use oil as a cooling medium, which is pumped through the generator

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single phase emf has i) conductor loop

one

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three phase emf has i) conductor loop i) apart

three, 120deg

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the armature in an alternator is i) while the field ii)

stationary, rotates

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the armature in a generator i)

rotates

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what are the advantages of an alternator

lighter rotating assembly

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What is the key difference between AC generators and AC brushless generators?

AC brushless generators have no slip rings or brushes

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AC brushless generators have a lower i) compared to AC generators

maintenance cost

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AC brushless generators is more i) and ii) compared to AC generators

stable and consistent

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AC brushless generators have i) at high altitudes, eliminating ii)

better performance, arcing

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The DC exciter in a AC brushless generator receives i) from ii)

DC field, voltage regulator

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The AC exciter in a AC brushless generator generates i) for ii)

power, main generator field

The Rotating Rectifier assembly(rotor) in a AC brushless generator rotates with i) and converts ii) to iii)

rotor shaft, AC Exciter output, DC

The Main generator (AC output stator) in a AC brushless generator supply i) to ii). Its iii) is connected to a iv)

AC output, load, output, voltage regulator

Line voltage in a Star connected system =

√3 Vphase

Line current in a Star connected system =

Iphase

Line voltage in a Delta connected system =

Vphase

Line current in a Delta connected system =

√3 Iphase

(Z) represents

Impedance

(L) represents

Inductance

Capacitance

(XL) represents

Inductive Reactance

(XC) represents

Capacitive Reactance

Formula for impedance

Z = R + XL + XC

Formula for inductive reactance

insert image

Formula for capacitive reactance

insert image

impedance of each phase is i) in balanced loads

equal

impedance of each phase is i) in unbalanced loads

not equal

the current flowing through the neutral wire in balanced loads = i) Amps

zero

true or real power is measured in i)

watts (W)

true or real power is consumed by i)

resistive loads

true or real power is denoted by i)

reactive power is measured in i)

volt-amps (VA)

reactive power is consumed by i)

inductive or capacitive loads

reactive power is denoted by i)

apparent power is measured in i)

volt-amps-reactive(VAR)

apparent power is consumed by i)

by entire circuit

apparent power is denoted by i)

Power factor (PF) is the ratio of i) to ii)

true power, apparent power

power factor is the measure of i) and is ideally ii)

the circuit's efficiency, 1

AC motors takes in i) as input and produces ii)

electrical energy, mechanical energy/work

AC motors are not 100% efficient because

encounter power losses in motor windings, losing electric energy in form of heat energy

generator produces i)

electrical energy

motor produces i)

mechanical energy/work

in synchronous motors, comment on the speed differences or similarities

speed of rotor is equal to speed of magnetic field

in asynchronous motors, comment on the speed differences or similarities

speed of rotor is not equal to speed of magnetic field

single phase synchronous motor is similar to i)

alternator with rotating field

single phase synchronous motor can be used as a i) or ii)

generator or motor

if a single phase synchronous motor were to be used as a motor, its i) must be constant to ensure ii) is also constant

input power frequency, motor speed

if a single phase synchronous motor were to be used as a generator, its i) must be constant to ensure ii) is also constant

speed, output frequency

in a three phase synchronous motor, its rotor winding is energized with i) and acts like a ii)

DC power, bar magnet

in a three phase synchronous motor, its rotor winding i) with the ii)

rotates, rotating field at the stator

in a three phase synchronous motor, its rotor runs at i) as the rotating magnetic field and thus is said to be ii)

the same speed, synchronous

in induction motors, the i) interacts with the ii) , creating a iii)

rotor flux, rotating flux, mechanical force

in induction motors, the mechanical force produced by the interaction between the rotor flux and the rotating flux causes i)

the rotor to rotate in the same direction as the rotating magnetic field

in three-phase induction motors, the i) cuts the ii). This induces iii) in the rotor conductors causing iv), producing a v)

rotating stator magnetic field, stationary rotor conductors, voltage, currents to flow in the short circuited rotor bars, a rotor flux

in three phase induction motors, why must the rotor run at a slightly lower speed than the rotating magnetic field

if speed is equal, will be no flux cut. Hence no voltage induced in rotor conductor, resultant current and torque developed = 0

Why large induction motors are started with reduced current?

high current can cause momentary dip in voltage, affecting other equipment connected to same power supply

single phase induction motors are more advantageuous because it is i), ii) and iii)

small, less expensive, does not require a 3 phase power supply

single phase induction motors isnt able to i) and requires a ii)

self start, self starting scheme

why are single phase induction motors less efficient compared to 2 or 3 phase motors

it has a pulsating field, thus has pulsating torque which is less efficient to 2 or 3 phase motors where the torque is more uniform

A balanced, star connected 3 phase synchronous motor drew a 10A line current. The same motor will draw i) line current when it is delta-connected

(3*10) A

Three phase induction motors can also be known as

a squirrel cage induction motor

Shaded pole induction motors are a i)

type of single phase AC motor

If the line currents of a 3 phase circuit are not spaced 120deg apart, it is because

the loads are not balanced

A 3-phase, balanced, star connected heater load is connected to a RYB sequenced, 200VAC/400hz star connected supply. VBN =

200 ∠ -240° VAC

when the reactive power of a 3-phase AC machine is reduced while the real power is maintained, the i)

apparent power will tend towards real power

RYB Sequence is

positive

RBY Sequence is

negative