WorksheetsPower Electronics
Total questions: 40
Worksheet time: 40mins
In the ___________ type of chopper, two stage conversions takes place.
AC-DC
AC link
DC link
None of the mentioned
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
The values of duty cycle (α) lies between..........
1<α<100
0<=α<=1
0>α>-1
0<α<1
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
In case of multiple pulse width modulation method, if the amplitudes of the reference wave and the carrier wave are made equal then, the pulse width =
100 °
∞
0
none of the mentioned
Dual converters provide
two quadrant operation
three quadrant operation
four quadrant operation
none of the mentioned
A dual converters has
two full converters in series
two half converters in series
two full converters in anti-parallel
two half converters in anti-parallel
The major advantage of using dual converters is that
it is cheaply available
no mechanical switch is required to change the mode of operation
it has better pf
its operating frequency is very high
The four quadrant operation of dual converters can be obtained by
moving the mechanical lever
changing the firing angle value
adding inductance to the circuit
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
In the above circuit, the right side converter C2 operates in the ___ and ___ quadrant.
second, fourth
first, fourth
second, third
first, third
Name the below given circuit.
Single-phase dual converter circulating current type
Single-phase dual converter non-circulating current type
Three-phase dual converter non-circulating current type
Three-phase dual converter circulating current type
In non-circulating current mode dual converters, the circulating current is avoided by
connecting a series reactor
maintaining α1 + α2 = 180°
adding an extra SCR
operating only one converter
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
Name the following circuit
Three-phase dual converter with non-circulating current type
Single-phase dual converter with circulating current type
Three-phase dual converter with circulating current type
Single-phase dual converter with non-circulating current type
1. In case of three-phase dual converter, one of the converter circuits is fired at an angle of 60°. For both the converter circuits to have equal average output voltage, what is the value of the firing angle for the other converter circuit?
60°
120°
100°
Insufficient data
In case of circulating current type dual converters, the reactor is inserted between
no reactor is used in case of circulating type dual converter
across the load
supply and converter
between the converters
Choose the correct statement.
Circulating current type is faster in operation
Non-circulating current type is faster in operation
Both the types have the same speed of operation
Circulating current improves power factor
Circulating current flows
from load to converters
from one converter to another converter
in the whole circuit
none of the mentioned
The reactor in circulating current type dual converters
increases losses
reduces power factor
increase the weight of the circuit
all of the above
If V1 and V2 are the instantaneous voltages of the two converter circuits in the dual convert, then the output voltage is
2(V1 + V2)
V1 + V2
V1 – V2
(V1 + V2)/2
A single-phase semi-converter is having continuous conduction, as such each thyristor will conduct for an angle of
α
π
α+π
π-α
All the modern AC-DC converters are using GTOs instead of SCRs because
emperature is an issue in SCRs
Switching losses are high in SCRs
GTOs have reliable commutation
GTOs are cheaply available today
Find the average output dc voltage of a single-phase semi-converter with Vs=230 V and firing angle of 30°. The converter is operating under continuous conduction.
256 V
0 V
230 V
193 V
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
In a voltage commutated SCR, the main SCR is commutated by
triggering the auxiliary SCR
sending a negative pulse to the main SCR
removing the supply Vs
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
In the single-pulse width modulation method, the output voltage waveform is symmetrical about __________
π
2π
π/2
π/4
n the single-pulse width modulation method, the output voltage waveform is symmetrical about ____________ in the negative half cycle.
3π/2
π/2
3π/4
2π
The shape of the output voltage waveform in a single PWM is
quasi-square wave
sine wave
triangular wave
square wave
