Worksheetsimportant quizz IE
Total questions: 82
Worksheet time: 1hrs 22mins
Name
Class
Date
1.
The three terminals of the IGBT are
a)
base, emitter & collector
b)
gate, source & drain
c)
gate, emitter & collector
d)
base, source & drain
2.
IGBT possess
a)
low input impedance
b)
high input impedance
c)
high on-state resistance
d)
second breakdown problems
3.
Which of the following diodes uses a metal-semiconductor junction?
a)
General purpose diodes
b)
Fast recovery diodes
c)
Schottky diode
d)
Slow recovery diode
4.
The V-I Characteristics of the diode lie in the
a)
1st & 2nd quadrant
b)
1st & 3rd quadrant
c)
1st & 4th quadrant
d)
Only in the 1st quadrant
5.
The TRIAC can be represented by
a)
two SCRs in anti-parallel
b)
two SCRs in parallel
c)
two diodes in anti-parallel
d)
two diodes in parallel
6.
two diodes in parallel
a)
forward current rating
b)
breakover voltage
c)
holding current
d)
latching current
7.
If the cathode of an SCR is made positive with respect to the anode & no gate current is applied then
a)
all the junctions are reversed biased
b)
all the junctions are forward biased
c)
only the middle junction is forward biased
d)
only the middle junction is reversed biased
8.
The GTO (gate turn-off thyristor) is a
a)
p-n-p-n device
b)
p-n-p device
c)
p-metal-n device
d)
p-n single junction device
9.
For an SCR in the reverse blocking mode, (practically)
a)
leakage current does not flow
b)
leakage current flows from anode to cathode
c)
leakage current flows from cathode to anode
d)
leakage current flows from gate to anode
10.
A GTO can be turned on by applying
a)
Positive gate signal
b)
Positive drain signal
c)
Positive source signal
d)
by a negative gate pulse
11.
In a battery charging circuit,SCR will act as a
a)
CHOPPER
b)
RECTIFIER
c)
CYCLOCONVERTOR
d)
INVERTOR
12.
In a normal operating condition,a Zener diode in a Crowbar protection circuit will act as a
a)
Open Switch
b)
Closed Switch
c)
Switch
d)
Protects the Load
13.
For an SCR, dv/dt protection is achieved through the use of
a)
R in parallel with SCR
b)
L in paralle with SCR
c)
RC in paralle with SCR
d)
RLC in paralle with SCR
14.
A freewheeling diode placed across a RL load provides
a)
demagnetisation path for inductor
b)
demagnetisation path for resistor
c)
demagnetisation path for switch
d)
magnetisation path for inductor
15.
A three phase full wave rectifierwill require __________ number of SCRs.
a)
3
b)
6
c)
9
d)
2
16.
By using a freewheeling diode (FD) in a rectifier with RL load, the power consumed by the load
a)
increases
b)
decreases
c)
is not affected
d)
decreases to zero
17.
Name the parameter which is kept constant in frequency modulation control in a chopper
a)
T
b)
Ton
c)
Toff
d)
Either Ton or Toff
18.
In which quadrant CLASS A CHOPPER is working ?
a)
1ST QUADRANT
b)
2ND QUADRANT
c)
3RD QUADRANT
d)
4RTH QUADRANT
19.
Name the chopper in which output voltage is less than input voltage
a)
Step up Chopper
b)
Step down Chopper
c)
BuckBoost
d)
Boost
20.
Which converter will give an output voltage which is always greater than the Input voltage?
a)
Buck Converter
b)
Boost Converter
c)
Buck Boose Converter
d)
buck Converter
21.
What is the voltage equation of step up / down chopper with α as the duty cycle and Vs as the dc input voltage is
a)
Vs / (1 – α)
b)
α x Vs
c)
Vs * α / (1-α)
d)
Vs * α/ (1+α)
22.
What will be the output voltage of a buck converter with an input voltage of 25V, 40% duty cycle?
a)
12
b)
10
c)
12.5
d)
11.1
23.
What will be the output voltage of a boost converter with an input voltage of 50V, 65% duty cycle?
a)
32.5
b)
17.5
c)
142.8
d)
76.9
24.
Which power electronics switch can be the best for boost converter?
a)
SCR
b)
MOSFET
c)
Mechanical Switch
d)
TRIAC
25.
What is the duty cycle of a chopper ?
a)
Ton/Toff
b)
Ton/T
c)
T/Ton
d)
Toff x Ton
26.
To make a signal diode suitable for high current & high voltage carrying applications with minimum losses, ________
To make a signal diode suitable for high current & high voltage carrying applications with minimum losses, ________
To make a signal diode suitable for high current & high voltage carrying applications with minimum losses, ________
a)
a lightly doped n layer is grown between the two p & n layers
b)
a heavily doped n layer is grown between the two p & n layers
c)
a lightly doped p layer is grown between the two p & n layers
d)
a heavily doped p layer is grown between the two p & n layers
27.
An ideal power diode must have
a)
low forward current carrying capacity
b)
large reverse breakdown voltage
c)
high ohmic junction resistance
d)
high reverse recovery time
28.
The GTO can be turned off
a)
by a positive gate pulse
b)
by a negative gate pulse
c)
by a negative anode-cathode voltage
d)
by removing the gate puls
29.
A thyristor is reverse biased and a positive gate pulse is applied the thyristor
a)
will be turned on
b)
may or may not turn on
c)
will not turn on
d)
will turn on after sometime
30.
The SCR is turned -off when the anode current falls below_____
a)
Forward current
b)
Latching current
c)
Holding current
d)
Breakover current
31.
Class E commutation is a/an
a)
line commutation technique
b)
load commutation technique
c)
forced commutation technique
d)
external-pulse commutation technique
32.
In AC voltage regulator, TRIACS cannot be used for a
a)
Back emf load
b)
Resistive load
c)
R-L Load
d)
Inductive load
33.
The forward break over voltage is maximum when
a)
Gate current = ∞
b)
Gate current = 0
c)
Gate current = -∞
d)
It is independent of gate current
34.
Which among the following components is not used in an over voltage crowbar protection circuit?
a)
Resistor
b)
Capacitor
c)
Inductor
d)
SCR
35.
For an SCR, di/dt protection is achieved through the use of
a)
R in series with SCR
b)
L in series with SCR
c)
RL in series with SCR
d)
RLC in series with SCR
36.
A freewheeling diode placed across a RL load provides
a)
fast turn-on time
b)
slow turn-off time
c)
poor utilization factor
d)
better power factor
37.
What is the angle of conduction of diode in a 3phase rectifier?
a)
180°
b)
120°
c)
90°
d)
60
38.
Choose the requirements to turn-on the thyristors in a controlled full-wave rectifiers.
a)
The anode terminal of the thyristors is negative.
b)
The cathode terminal of the thyristor is positive.
c)
The half-cycle of the AC supply voltage is positive.
d)
Applying a control signal to the gate terminal of the thyristors.
39.
If T is the time period for a chopper circuit and α is its duty cycle, then the chopping frequency is
a)
Ton/α
b)
Toff/α
c)
α/Toff
d)
α/Ton
40.
In which quadrant CLASS C CHOPPER is working ?
a)
1ST QUADRANT
b)
1ST AND 2ND QUADRANT
c)
3RD QUADRANT
d)
2ND AND 3RD QUADRANT
41.
What type of conversion takes place in a Chopper?
a)
AC to DC
b)
DC to AC
c)
DC to DC
d)
AC to AC
42.
What will be the output voltage for a Buck-Boost Converter, if α = 0.5?
a)
Vo = Vs
b)
Vo < Vs
c)
Vo > Vs
d)
Data insufficient
43.
Find the odd one
a)
Buck Boose Converter
b)
Forward Converter
c)
Boost Converter
d)
Buck Converter
44.
Find the output voltage expression for a boost converter with Vs as the input voltage and α as the duty cycle.
a)
Vo = Vs/α
b)
Vo = Vs x α
c)
Vo = Vs/(1-α)
d)
Vo = 2Vs/απ
45.
What is the main disadvantage for Buck Boost Converter?
Choices:
a)
Fixed output voltage
b)
Inverted Output
c)
Output is variable
d)
Zero output voltage
46.
The softness factor for soft-recovery and fast-recovery diodes are respectively
a)
1, >1
b)
<1, 1
c)
1, 1
d)
1, <1
47.
A diode is said to be reversed biased when the
a)
cathode is positive with respect to the anode
b)
anode is positive with respect to the cathode
c)
cathode is negative with respect to the anode
d)
both cathode & anode are negative
48.
A diode is said to be forward biased when the
a)
cathode is positive with respect to the anode
b)
anode is positive with respect to the cathode
c)
anode is negative with respect to the anode
d)
both cathode & anode are positive
49.
The approximate equivalent circuit of an IGBT consists of
a)
a BJT & a MOSFET
b)
a MOSFET & a MCT
c)
two BJTs
d)
two MOSFETs
50.
The SITH (Static Induction Thyristor) is a
a)
4 terminal, self-controlled device
b)
3 terminal, self-controlled device
c)
4 terminal, un-controllable device
d)
3 terminal, un-controllable device
51.
Why an SCR is considered to be a semi controlled device because
a)
it can be turned OFF but not ON with a gate pulse.
b)
it conducts only during one half cycle of an alternating current wave.
c)
it can be turned ON but not OFF with a gate pulse.
d)
it can be turned ON only during one half cycle of an AC.
52.
Natural commutation of an SCR takes place when
a)
voltage across the device becomes negative
b)
voltage across the device becomes positive
c)
gate current becomes zero
d)
anode current becomes zero
53.
dv/dt protection is provided to the SCR by
a)
connecting a capacitor in parallel with the load
b)
connecting an inductor in series with the load
c)
connecting a capacitor & resister in parallel with the device
d)
connecting an inductor & resister in parallel with the device
54.
In the process of diode based rectification, the alternating input voltage is converted into
a)
an uncontrolled alternating output voltage
b)
an uncontrolled direct output voltage
c)
a controlled alternating output voltage
d)
a controlled direct output voltage
55.
In a single-phase half-wave circuit with RL load and a freewheeling diode, the load voltage during the freewheeling period will be
a)
zero
b)
positive
c)
negative
d)
positive than negative
56.
Name the chopper which combines the function of both class A and class B chopper.
a)
CLASS D CHOPPER
b)
CLASS E CHOPPER
c)
CLASS C CHOPPER
d)
VOLTAGE COMMUTATED CHOPPER
57.
A chopper may be thought as a
a)
Inverter with DC input
b)
DC equivalent of an AC transformer
c)
Diode rectifier
d)
DC equivalent of an induction motor
58.
Which of the following is true in case of a power diode with R load?
a)
I grows almost linearly with V
b)
I decays almost linearly with V
c)
I is independent of V
d)
I initial grows than decays
59.
From the following list of devices, choose the device that only turns-on for a fixed-value of anode-cathode voltage
a)
PUT
b)
SCR
c)
SUS
d)
BJT
60.
Which semiconductor power device out of the following, is not a current triggering device?
a)
Triac
b)
G.T.O
c)
MOSFET
d)
SCR
61.
The three terminals of MCT
a)
Anode, cathode, gate
b)
Collector, emitter, gate
c)
Drain, source, base
d)
Drain, source, gate
62.
Natural commutation of an SCR takes place when
a)
voltage across the device becomes negative
b)
voltage across the device becomes positive
c)
gate current becomes zero
d)
anode current becomes zero
63.
Crowbar circuit is used to protect the device from
a)
Over current
b)
Over Voltage
c)
Short ciruit
d)
Over Load
64.
Which of the following does not cause permanent damage of an SCR?
a)
High current
b)
High rate of rise of current
c)
High temp. rise
d)
High rate of rise of voltage
65.
Name the chopper which works in all four quadrants.
a)
CLASS D CHOPPER
b)
CLASS B CHOPPER
c)
CLASS C CHOPPER
d)
CLASS E CHOPPER
66.
The load voltage of a chopper can be controlled by varying the __________.
a)
duty cycle
b)
firing angle
c)
reactor position
d)
extinction angle
67.
A thyristor can be bought from the forward conduction mode to forward blocking mode by
a)
the dv/dt triggering method
b)
applying a negative gate signal
c)
applying a positive gate signal
d)
applying a reverse voltage across anode-cathode terminals
68.
Name the parameter which is varying in frequency modulation control in a chopper
a)
FREQUENCY
b)
TIME PERIOD
c)
TON
d)
TOFF
69.
Name the parameter which is kept constant in pulse width modulation control in a chopper
a)
Vs
b)
Ton
c)
T
d)
Toff
70.
Type C chopper consists of
a)
two diodes and two switches
b)
one diode and one switch
c)
one diode and three switches
d)
three diodes and two switches
71.
What will be the output voltage for a Buck-Boost Converter, if α < 0.5?
a)
Greater than input voltage
b)
Less than input voltage
c)
Same as Input
d)
Data insufficient
72.
What is the range of duty cycle (α)?
a)
0<α<1
b)
0>α>-1
c)
0<=α<=1
d)
1<α<100
73.
Which following is a two terminal three layer device?
a)
MOSFET
b)
BJT
c)
POWER DIODE
d)
SCR
74.
Choose one important property of an LASCR
a)
can conduct in both directions
b)
has a built in anti parallel diode
c)
is preferred in high voltage and high current applications where optical isolation is used between trigger source and switching device
d)
can be turned off by negative gate signal
75.
In a half-wave rectifier with L Load, the
a)
current & voltage both are bi-directional
b)
current & voltage both are uni-directional
c)
current is always uni-directional but the voltage can be bi-directional
d)
current can be bi-directional or uni-directional but the voltage is always uni-directional
76.
In UNCONTROLLED rectifiers with resitive , load current flow is
a)
Unidirectional
b)
Bidirectional
c)
Either (a) or (b)
d)
Negative
77.
A reverse conducting thyristor (RCT) normally replaces
a)
A pair of anti parallel thyristors in a circuit
b)
A combination of thyristor and an anti parallel diode in a circuit
c)
A thyristor in saturation where it is not required to have reverse blocking capability at all
d)
Conventional conversion grade thyristors having large turn off time
78.
In a SCR circuit, the angle of conduction is changed by changing______
a)
Anode voltage
b)
Gate current
c)
Forward current
d)
Anode current
79.
Which terminal does not belong to the SCR?
a)
Anode
b)
Gate
c)
Base
d)
Cathode
80.
The natural reversal of ac supply voltage commutates the SCR in case of
a)
forced commutation
b)
only line commutation
c)
only natural commutation
d)
both line & natural commutation
81.
In a three-phase half wave diode rectifier using 3 diodes,
a)
All diodes conduct together
b)
Only two diodes conduct at a time
c)
Only one diode conducts at a time
d)
Diodes will not conduct
82.
In case of controlled rectifiers, the nature of the load current (continues or discontinuous) depends upon the
a)
type of load and firing angle
b)
only on the type of load
c)
only on the firing angle
d)
it is independent of all the parameters
100 %
