WorksheetsEE501
Total questions: 50
Worksheet time: 27mins
Synchronous Machine operates in
synchronous speed
above synchronous speed
below synchronous speed
don't know
The salient-pole construction for field structure of an alternator is generally used for ................ machine
2-pole
4-pole
6-pole
8-pole
Synchronous Machine is
doubly excited system
singly excited system
A 10 pole AC generator rotates at 1200 rpm. The frequency of AC voltage in cycles per second will be
(a)
Which type of rotor is best for a turbo-alternator?
Salient pole type
Cylindrical rotor type
Salient pole & Cylindrical rotor
Non-salient pole type
How is the hydro-generator driven by?
water turbine
steam turbine
internal combustion engines
control of reactive power networks
What is the rating of the hydro-generators?
750 MW
1000 MW
20 MW
70 MW
What is the speed by which the hydro-generators are driven?
100-1000 rpm
5000 rpm
1500 rpm
3000 rpm
The prime movers used to drive projected pole type alternator is
Water turbines
I.C. engines
Steam turbines
both water turbines and I.C. engines
The air gap in a salient pole machine is
(a)
Speed of cylindrical pole alternator compare to salient pole alternator is
high
low
Which not the part of synchronous machine
AVR
Starter
Cooling Fan
Brush
Which not the part of synchronous machine
Rotor
Commutator
Exciter
Encloser
Salient Pole Rotor have
less no of stator pole
large no of stator pole
Cylindrical Rotor have
less no of stator pole
large no of stator pole
Turbo Alternators
diameter is small but axial length is large
large diameter but small axial length
Hydro Alternators
diameter is small but axial length is large
large diameter but small axial length
Hydro Alternators rotates at
high speed
low speed
Turbo Alternators rotates at
high speed
low speed
Which one is used to charge battery
Automotive Type Alternator
Diesel Electric Locomotive Type Alternator
Marine Type Alternator
Brush less Type Alternator
Radio Alternators Alternator
Which one is used as power supply
Automotive Type Alternator
Diesel Electric Locomotive Type Alternator
Marine Type Alternator
Brush less Type Alternator
Radio Alternators Alternator
In Alternator
Magnetic Field rotates
Armature rotates
Which is not the function of Excitation system
Maintain the voltage
Control reactive power
Improve static and transient stability
Maintain the electrical output power
Main exciter is
separately excited DC generator
self-excited DC generator
DC excitation system has
one exciters
two exciters
AVR regulate
main exciter output
pilot exciter output
In which excitation system DC output of rotating rectifier is directly fed to main generator field
Static Excitation
Brush less Excitation System
AC Excitation
DC Excitation
In alternator output power is depend on
Alternator power
Excitation power
Primover power
Excitor power
In synchronous motor rotor, copper losses are met by
Supply Mains
Armature Input
DC Source
AC Input
The output frequency of an alternator depends on
Number of poles and rotational speed
Numbers of poles only
Rotational speed only
Types of winding
The power factor of an alternator depends on
Armature losses
Type of Load
Core Losses
Speed of Motor
Negative voltage regulation can be expected in case of
High-speed alternator
Slow speed alternator
Leading power factor load
Lagging power factor load
A 10 pole 25 Hz alternator is directly coupled to and is driven by 60 Hz synchronous motor then the number of poles in a synchronous motor is?
24 poles
12 poles
6 poles
3 poles
Turbo alternators have rotors of
Small diameter and long axial length
Large diameter and long axial length
Large diameter and small axial length
Small diameter and axial length
The advantages of having the revolving field of the alternator are
Ease of construction
Better Insulation to the armature
Reduce Rotor weight
Reduce machine cost
For the same power rating, an alternator is .................... that of a d.c. generator
Medium in size than
Of the same size as
Smaller in size than
Larger in size than
What happens if field winding of the synchronous motor is short circuited?
First, starts as induction motor then run as synchronous motor
Not start
Motor will burn out
Run as induction motor
In de-magnetizing armature reaction armature mmf
change main magnetic field
distort main magnetic field
assist main magnetic field
oppose main magnetic field
In magnetizing armature reaction armature mmf
change main magnetic field
distort main magnetic field
assist main magnetic field
oppose main magnetic field
In cross-magnetizing armature reaction armature mmf
change main magnetic field
distort main magnetic field
assist main magnetic field
oppose main magnetic field
armature mmf is the product of
current and turn
voltage and current
power and current
force and current
Armature reaction directly depends on
load voltage
load power factor
load power
load current
Ideally the voltage regulation of an alternator should be ___________
infinite
100%
50%
zero
If the machine size increases, the three phase alternator resistance _______ and synchronous reactance _______
decreases, increases
remains constant, decreases
increases, decreases
decreases, decreases
If the emf from the air gap line is the 3-phase alternator is 440V per phase and armature current is 110 A. The synchronous reactance is?
6.92 ohms
2 ohms
4 ohms
2.32 ohms
The emf method of the voltage regulation is applicable only to cylindrical rotor alternator due to ___________
resultant air gap flux is not affected by angular position of rotor
uniform angular position of rotor
non uniform angular position of rotor
saliency of the poles is a trouble while estimating the emf
When the load on an alternator is varied, its terminal voltage also changes due to _____________
armature resistance
leakage reactance
armature reaction
all of the mentioned
amount of leakage flux is depends on
core current density
core flux density
core reactance
core resistance
emf induced in armature due to
leakage flux
mutual flux
Synchronous reactance of an alternator represents
armature reactance and leakage reactance
a reactance operating at synchronous speed
field winding reactance
all of the above
