AEIS CHAPTER 1 Flashcards
What is the Formula for EMF
e = Blvsinθ
e in e = Blvsinθ represents
emf
B in e = Blvsinθ represents
flux intensity
l in e = Blvsinθ represents
conductor length
v in e = Blvsinθ represents
speed of conductor cutting the flux lines
θ in e = Blvsinθ represents
relative angle between conductor and flux lines
What is the Formula for frequency
f = NP/120
N in f = NP/120 represents
conductor rotation speed in rpm
P in f = NP/120 represents
number of poles in machine
What is a CSD/CSU
Constant Speed Drive/Unit
What is the purpose of a CSD/CSU?
to ensure alternator will produce a constant output frequency and voltage regardless of engine speed
IDG =
Integrated Drive Generator
IDG consists of
CSD + Generator mounted side by side into one compact unit
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
single phase emf has i) conductor loop
one
three phase emf has i) conductor loop i) apart
three, 120deg
the armature in an alternator is i) while the field ii)
stationary, rotates
the armature in a generator i)
rotates
what are the advantages of an alternator
lighter rotating assembly
What is the key difference between AC generators and AC brushless generators?
AC brushless generators have no slip rings or brushes
AC brushless generators have a lower i) compared to AC generators
maintenance cost
AC brushless generators is more i) and ii) compared to AC generators
stable and consistent
AC brushless generators have i) at high altitudes, eliminating ii)
better performance, arcing
The DC exciter in a AC brushless generator receives i) from ii)
DC field, voltage regulator
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
(C) represents
Capacitance
(XL) represents
Inductive Reactance
(XC) represents
Capacitive Reactance
Formula for impedance
Z = R + XL + XC
Formula for inductive reactance
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Formula for capacitive reactance
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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)
P
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)
Q
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)
S
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
