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WorksheetsComprehensive_viva_part2
Total questions: 138
Worksheet time: 1hrs 24mins
In Synchronous Generator, which of the following coils will have emf closer to sine wave form?
Concentrated winding in full pitch coils
Concentrated winding in short pitch coils
Distributed winding in full pitch coils
d) Distributed winding in short pitch coils.
The negative phase sequence in a three phase synchronous motor exists when the motor is……..
Under loaded
Over loaded
Supplied with unbalanced voltage
Hot
A constant voltage generator has
Minimum efficiency
Low internal resistance
High internal resistance
Minimum current capacity
In a synchronous generator a divided winding rotor is preferable to a conventional winding factor is preferable to a conventional winding rotor because of
Higher efficiency
Increased steady-state stability limit
Higher SCR ration
Better damping
Which of the following methods would give a higher than actual value of regulation of an alternator?
ZPF method
MMF method
EMF method
ASA method
If the excitation of a 3-Phase alternator operating on infinite bus bars is changed, which of the following shall alter?
Active power of machine
Reactive power of machine
Terminal voltage of machine
Frequency of machine
The main advantage of distributing the winding in slots is to
Reduce the size of the machine
Add mechanical strength to the winding
Reduce the amount of copper required
Reduce the harmonics in the generated EMF.
In synchronous machine, damper windings are used to
Help in starting as a motor
Run it as an induction motor
Help in starting as a motor and to reduce hunting
Increase efficiency
In an alternator, armature reaction is considered equivalent to
Fictitious impedance
Fictitious conductance
Fictitious resistance
Fictitious reactance
To reduce the harmonics in the emf generated in an alternator
Slots are skewed
Salient pole tips are chamfered
Winding is well distributed
All of the above.
The a.c. the armature winding of an alternator is
Delta Star connected
Generally Delta Connected
Star Delta Connected
Always Star connected
The pitch factor for a full pitch winding of a synchronous machine is
0
0.5
0.9
1
In the case of Zero Power factor leading load on the alternator, the effect of armature reaction is
To demagnetize
To increase induced EMF
To cross -Magnetize
To decrease the Induced EMF
The Output frequency of an alternator depends on
Type of winding
Number of poles and rotational speed
Number of poles only
Rotational speed only
The power factor of an Alternator depends on
Speed of Motor
Core losses
Armature losses
Type of load
When the power factor of an alternator is unity then the armature flux will be
Demagnetization
Cross-Magnetization
Zero
Operating at high RPM
For a 50Hz ,2-Pole the maximum speed of an alternator is
6000
2500
4000
3000
In 3-Phase Synchronous motor if one of the phases is short circuited the motor will
Run as before
Overheated and eventually burn
Not start
Burn
For a Synchronous motor, the breakdown torque will be proportional to
Applied voltage V
V2
1/V
1/V2
In a Synchronous motor, at no-load, and condition, and with normal excitation the
Armature current drawn by a synchronous motor is
Zero
Lagging applied voltage by 90
Leading Applied voltage by 90
In phase with applied voltage
In a Synchronous motor, ”Hunting” may be due to variation in any of the following
EXCEPT
Winding friction
Frequency
Load
Supply Voltage
A capacitor start single phase induction motor will usually have a power factor of
unity
0.8 leading
0.6 leading
0.6 lagging
A capacitor start, capacitor run single phase induction motor is basically a
ac series motor
dc series motor
2 phase induction motor
3 phase induction motor.
The starting torque of a capacitor start motor is
zero
Low
same as rated torque
more than rated torque
The torque developed by a split phase motor is proportional to
Sine of angle between lm and ls
Cosine of angle between lm and Is
Main winding current, Im
Auxiliary winding current,Is
A capacitor start single phase induction motor is switched on the supply with its capacitor
replaced by an inductor of equivalent reactance value. It will
not start
start and run
start and then stall
none of the above
The starting capacitor of a single phase motor is
Electrolytic capacitor
Ceramic capacitor
Paper capacitor
None of the above.
Which of the following is the most economical method of starting a single phase motor
Resistance start method
Inductance start method
Capacitance start method
Split-phase method
The number of turns in the starting winding of a capacitor start motor as compared to that for split phase motor is
same
more
less
none of the above
In a split phase motor, the ratio of number of turns for starting winding to that for running winding is
2.0
more than 1
1.0
less than 1.
A single phase motor generally used for small air compressor is
capacitor start capacitor run motor
reluctance motor
universal motor
shaded pole motor.
Out of the following motors, which will give the highest starting torque
Universal motor
Capacitor start motor
Shaded pole motor
All have zero starting torque.
Which single phase ac motor will you select for record players and tape recorders ?
Hysteresis motor
Shaded pole motor
Reluctance motor
Two value capacitor motor
A universal motor is one
which can run on any value of supply voltage
which has infinitely varying speed
which can operate on ac as well as dc voltage
which can work as single phase or three phase motor.
The motor used in household refrigerators is
dc series motor
dc shunt motor
universal motor
single phase induction motor
Single phase motors are commercially manufactured up to
1H.P.
2 H.P.
5 H.P.
10 H.P.
The direction of rotation of universal motor can be reversed by
reversing the supply terminals
switching over from ac to dc
interchanging the brush leads
any of the above.
synchronous motor works on the principle of
Mutual Induction
Electromagnetic induction
Magnetic locking
None of these
Synchronous motors are
Self Starting
Not self starting
Both (a) and (b)
None of these
The method used for starting of synchronous motor is/are
Using pony motor
Using Damper winding
As a slip ring induction motor
All of the above
Fill in the blank . Power Electronics circuits involve______________ from one form to another using power semiconductor devices
Application of power electronics in static system is......
How to increase the current conducting capability of diode?
The controlling parameter in MOSFET is the......
Which of the following statement is correct for an SCR operating in REVERSE BLOCKING MODE - practical condition
Three types of common power transistor are.....
A single-phase half-wave type diode rectifier requires __________ number of diode(s) whereas full wave type requires _________ number of diode(s)
For a certain diode based rectifier, the output voltage (average value) is given by the equation 1/2π ∫Vm sin (ωt) dωt ; where the integral (∫) runs from 0 to π. The rectifier configuration must be that of a....
With respect to the given circuit, from ωt = 0 to α, thyristors _____________ block the forward voltage.
Fill in the blank . Power Electronics circuits involve______________ from one form to another using power semiconductor devices
Application of power electronics in drive system is...... (2 marks)
Choppers is..................converter
AC -DC
DC-AC
AC-AC
DC-DC
A chopper may be thought as a
Inverted with DC input
DC equivalent of an AC transformer
Diode rectifier
DC equivalent of an induction motor
Which device can be used in a chopper circuit?
BJT
MOSFET
GTO
ALL THE ABOVE
What is the duty cycle of a chopper ?
Ton/Toff
Ton/T
T/Ton
Toff x Ton
The load voltage of a chopper can be controlled by varying the..................
duty cycle
firing angle
reactor position
extinction angle
In a half wave bridge inverter circuit, the power delivered to the load by each source is given by
2(Vs x Is)
Vs x Is
(Vs x Is)/2
None of the mentioned
The series-inverter control method is a/an..........
external frequency control method
external voltage control method
internal voltage control method
none of the mentioned
A single full converter alone can given a
two quadrant operation
three quadrant operation
four quadrant operation,
none of the mentioned
Choose the correct statement
Circulating current exists only in circulating current mode
Circulating current exists in both the circulating and non-circulating current mode
Circulating current exists only in non-circulating current mode
none of the mentioned
The process of commutating a SCR by applying a reverse voltage to an SCR through a previously charged capacitor is called as
capacitor commutation
forced commutation
voltage commutation
current commutation
In case of current commutation of SCR
a diode is connected in parallel with the main SCR
a diode is connected in anti-parallel with the main SCR
a diode is connected in series with the main SCR
none of the mentioned
AC voltage controllers convertr is
fixed ac to fixed dc
variable ac to variable dc
variable ac to fixed ac
fixed ac to variable ac
In AC voltage controllers the
variable ac with fixed frequency is obtained
variable ac with variable frequency is obtained
variable dc with fixed frequency is obtained
variable dc with variable frequency is obtained
The AC voltage controllers are used in __________ applications.
electric heating
power generation
conveyor belt motion
power transmission
In the principle of phase control
control is achieved by adjusting the firing angle of the devices
the load is on for some cycles and off for some cycles
control is achieved by adjusting the number of on off cycles
control cannot be achieved
In the circuit shown in figure
only the negative cycle can be controlled
only the positive cycle can be controlled
both the cycles can be controlled
none of the mentioned
Application of Choppers including;
i. DC motor Drives
ii. trolley cars
iii. battery operated vehicles
iv. Switch mode power supply
i & iii
i & iv
i, ii & iii
i, ii, iii & iv
The Circuit Diagram is ideal circuit for
Buck Converter
Boost Converter
Buck-boost Converter
Identify two methods that used in controlling the switch in a chopper circuit.
Pulse Width modulation (PWM)
Phase angle Control
Variable Frequency Control
Square Wave Switching
SCR is defined as ...............
Silicone Cup Rectifier
Supply Controlled Rectifier
Silicone Controlled Rectifier
Shorted Controlled Rectifier
Which is the symbol of SCR?
Terminals of SCR are ..........
Anode and Cathode
Collector, Base and Emitter
Anode, Cathode and Gate
Drain, Source and Gate
Power Electronics can be defined as ...........
A conversion from Alternating Current to Direct Current of Power Supply
A conversion of DC power supply to AC power supply
A conversion of AC power supply to AC power supply
A technology of converting electric power from one supply to another supply using electronic power devices.
The electronic devices below are unidirectional devices EXCEPT:
TRIAC
Diode
Silicone Controlled Rectifier
Diode pass ......... in one direction?
a) Voltage
b) Current
c) Both
d) None of these
A thyristor is basically_____
PNPN device
A set of SCRs
A combination of diac and triac
A set of SCR, diac and a triac
If holding current of a thyristor is 2 mA then latching current should be____
0.02
0.001
0.004
0.002
SMPS is used for
obtaining controlled ac power supply
switch from one source to another
storage of dc power
obtaining controlled dc power supply
Power converters can change one form of power to another form of power using semiconductor power devices.
True
False
Which semiconductor power device out of the following, is not a current triggering device?
Thyristor
Triac
GTO
MOSFET
A thyristor equivalent of a thyratron tube is a
DIAC
TRIAC
Silicon controlled rectifier
BJT
Secondary breakdown occurs in
MOSFET but not in BJT
Both MOSFET and BJT
BJT but not in MOSFET
None of the above
Which of the following devices should be used as a switch in a low power switched mode power supply (SMPS)?
GTO
MOSFET
TRIAC
SCR
Gate of MOSFET is insulated with layer of...?
SiO2
O2
Si
None
What is the full form of IGBT...?
Insulation gate bipolar transistor
Insulation gate bidirectional transistor
Insulated gate bipolar transistor
Insulated gate bidirectional transistor
Which of the following circuits will light up the bulb?
A
B
C
D
MCCB
Maine Circuit Breaker
Main Circuit Breaker
Main Circuit Braker
Maine Circuit Braker
MCCB
Maine Circuit Breaker
Main Circuit Breaker
Main Circuit Braker
Maine Circuit Braker
RCCB
Troop Circuit Breaker
Trap Circuit Breaker
Tripe Circuit Breaker
Trip Circuit Breaker
Remettre dans l'ordre :
SIDRECREVWR
(a)
H_ _ _ _ _
(a)
S_ _ _ _ _
(a)
an outlet in the USA (United States of America)
In the kitchen, there is...
a shower
an shower
a oven
an oven
In the bedroom there is...
a fridge
a lamp
an fridge
an lamp
fish tapes
/s/
/z/
/iz/
tool boxes
/s/
/z/
/iz/
flash lights
/s/
/z/
/iz/
insulated gloves
/s/
/z/
/iz/
Remettre dans l'ordre :
GUNDEROD
(a)
In the garden there (a) two plants.
In the office there (a) one desk
W_ _ _ _ _
(a)
Indice : un espace extérieur
TACRERE
(a)
Indice : on s'y essuie les pieds
ERANCNTE
(a)
Indice : on y trouve beaucoup d'eau
BHROTOAM
(a)
Indice : trop simple!
TILOTES
(a)
Appelé aussi 'cutter'
(a)
(a)
Pince à sertir
Diagonal pliers
End cutting pliers
Long nose pliers
Crimpers
Remettre dans l'ordre :
MITEUTEMLR
(a)
E_ _ _ _Y S_ _ _ _G B_ _B
(a)
F_ _ _ _ _ _ _ _ _ L_ _ _ _
(a)
In the garage this is (a) set of shelves
In the garage there is (a) car
In the garage there is (a) open door
La première pile électrique Volta a été inventée..
Autour de la révolution française (1789)
Autour de la Première Guerre Mondiale (1914-1918)
Autour de la Seconde Guerre Mondiale (1939-1945)
Autour de l'invention du Smartphone (1990)
Cet objet, inventé par Graham Bell est le tout premier...
lecteur de musique
microphone
téléphone
enregistreur
En 1888, George Bush invente le moyen de produire de l'énergie propre avec :
Le premier métro à utiliser l'énergie electrique est :
Le métro de Paris
Le métro de New York
Le métro de Tokyo
Le métro de Londres
La première voiture électrique date de 1899. Elle pouvait rouler à
30km/h
50km/h
100km/h
200km/h
La première centrale nucléaire en France.
1923
1963
1993
2013
56
fifteen-six
fifty-six
five hundred and six
five thousand and six
123
one twenty three
one hundred two three
one hundred twenty three
one thousand twenty three
The ball is _______ the box
above
between
under
next to
The box is _______ the ball
inside
under
between
next to
The fruit is _______ the boxes
on both side of
in front of
between
behind
The boxes are ________ the fruit
under
behind
inside
on both sides of
My name __ John
am
is
are
have
I __ 16 years old
am
is
are
have
I live ___ France
on
at
from
in
I come _____ France
in
at
from
on
Traduire: il y a deux radiateurs
(a)
Traduire: il y a quatre fenêtres
(a)
