NOBLE GROUP OF INSTITUTIONS, JUNAGADH
FACULTY OF ENGINEERING,
DEPARTMENT OF ELECTRICAL ENGINEERING
Subject/Subject Code
Semester/Branch
PE-II / 2160902
6th - Electrical
Question Bank
CHAPTER - 1
Q.1
Draw and explain the series Inverter circuit employing Class-A type commutation.
Draw and discuss the important waveforms.
Q.2
Design a series Inverter circuit for operation in the frequency range 1 to 5 kHz. The
load resistance may vary from 25% to 100%.The peak load current is limited to 3A
and the supply voltage is 100 V.
Q.3
A parallel capacitor commutated inverter with an Ideal transformer is supplying a
resistive load and has a very large smoothening reactor in the d.c. line. Draw a circuit
diagram, sketch the relevant wave forms and explain the operation.
Q.4
List various PWM methods used in inverters for Harmonic reduction and explain
Sinusoidal Pulse Modulation with necessary waveforms.
Q.5
Describe in brief about various methods of voltage control of single phase Inverter.
Q.6
Justify the sentence, “Space vector pulse width modulation (SVPWM) technique is
better than sine PWM technique”.
Q.7
Discuss 1-phase current source inverter.
Q.8
Explain PWM principle. Discuss selected harmonic elimination PWM technique to
eliminate 5th and 7th harmonics from the output voltage waveform.
Q.9
Explain Third harmonic PWM in detail with output waveforms.
Q.10
Explain working of three phase voltage source inverter with 120 degree conduction.
Draw Waveforms.
Q.11
Draw the power circuit of a parallel inverter and discuss its operation. Also explain
how voltage control can be obtained with this inverter.
Q.12
Describe using a neat circuit diagram, waveform and operation of PWM inverter and
also explain how the output voltage can be controlled in this scheme.
Q.13
A three phase bridge inverter has 180° conduction interval for it’s SCRs. Draw it’s
power circuit and state the conduction sequences of the SCRs with necessary
waveforms.
Q.14
Distinguish VSI and CSI and specify their applications.
NOBLE GROUP OF INSTITUTIONS, JUNAGADH
FACULTY OF ENGINEERING,
DEPARTMENT OF ELECTRICAL ENGINEERING
Q.15
Give classification of inverters on different basis. Compare Voltage source inverter
with Current source inverter in terms of its constructional features, working, relative
merits and demerits.
CHAPTER - 2
Q.1
Explain the operation of single phase A C voltage controller using two anti parallel
SCR’s with R-L load for firing angle α equal to and less than load phase angle phi.
derive relevant equation and draw the waveforms with neat circuit diagram.
Q.2
A single phase A C voltage controller with R-L load has the following details:
a. The control range of firing angle,
b. The maximum value of RMS load current,
c. The maximum power and power factor,
d The maximum values of average and RMS thyristor current
e. The maximum possible value of di/dt that may occur in the SCR and
f. The conduction angle α = 0 and α = 120° assuming a gate pulse of duration Π
radian.
Q.3
A single phase full wave ac controller has a resistive load of R=10 Ω and the input
voltage is 120 V (rms), 60 Hz. The delay angle of thyristor T1 and T2 are equal:
α1=α2=α=π/2. Find (a) rms value of output voltage, (b) the input PF, (c)average
current of thyristor and (d) rms current of thyristor.
Q.4
Explain effect of non sinusoidal supply voltage on AC motor operation. Also discuss
principle of variable frequency control.
Q.5
Discuss 3-phase full wave AC voltage controller with Y and Δ connected load.
Q.6
For a single phase full wave AC controller, the input rms voltage is Vs=120V, 60Hz.
The load is L=6.5 mH and R=2.5Ω.The delay angles of thyristors are equal i.e. α1=
α2=π/2. Determine (a) the conduction angle δ of the thyristor, which conducts for
positive half cycle (b) the rms output voltage Vo (c) the rms thyristor current IR (d)
the rms output current Io (e) the average current of a thyristor IA and (f) the input PF.
Q.7
Explain AC voltage controllers with PWM control
Q.8
Draw different configurations of three phase AC-AC Voltage controller. Write the
difference between them.
Q.9
Explain single phase AC-AC Controller (Regulator) with R-L Load. Derive equation
for Average and RMS output voltage.
Q.10
An a.c. voltage controller operating in integral cycle mode feeds a resistive load of 10
ohm from a single phase a.c. voltage source at 230 V, 50 Hz. The Thyristor switch is
on for 25 cycles followed by 75 cycles of extinction period. Determine (a) the r.m.s.
value of load voltage and load current. (b) The input power factor (c) the average
value of Thyristor current.
NOBLE GROUP OF INSTITUTIONS, JUNAGADH
FACULTY OF ENGINEERING,
DEPARTMENT OF ELECTRICAL ENGINEERING
Q.11
Compare on-off control & phase angle control of AC voltage controller
Q.12
A single phase full wave ac controller has R=10Ω, input voltage=120V(rms), 60Hz.
Delay angle α1=α2=л/2. Determine (a)Output Voltage (b)Average Thyristor current,
(c) Input PF.
CHAPTER - 3
Q.1
Describe the operating principle of single phase to single phase step
up bridge type cycloconverter. Illustrate your answer with appropriate
circuit and waveforms. The conduction of various thyristors must also
be indicated in the waveforms.
Q.2
With appropriate circuit diagram, equivalent circuit and waveform discuss single
phase to single phase cycloconverter.
Q.3
How load commutated cycloconverter is different than line commutated
cycloconverter? Explain with suitable load example.
Q.4
In a single phase to single phase cycloconverter, the input voltage is 120V(rms),60
Hz. The load resistance is 5Ω and the load inductance is L=40 mH. Thefrequency of
the output voltage is 20Hz. If the converters are operated as semi converters such that
0 ≤ α ≤ π and the delay angle is αp =2π/3, determine (a) the rms value of output
voltage Vo, (b) the rms current of each thyristor IR, and (c) the input PF.
Q.5
For a single phase full wave AC controller, the input rms voltage is Vs=120V, 60Hz.
The load is L=6.5 mH and R=2.5Ω.The delay angles of thyristors are equal i.e. α1=
α2=π/2. Determine (a) the conduction angle δ of the thyristor, which conducts for
positive half cycle (b) the rms output voltage Vo (c) the rms thyristor current IR (d)
the rms output current Io (e) the average current of a thyristor IA and (f) the input PF.
Q.6
Explain with neat diagram and waveforms the working of single phase
Cycloconverter
Q.7
Explain three phase Cycloconverter
Q.8
Distinguish circulating current mode and non-circulating current mode with
cycloconverter.
Q.9
Discuss in brief the matrix converter.
CHAPTER - 4
Q.1
Draw the circuit diagram and explain the working of slip power recovery system
using solid state scherbius system.
Q.2
Name the different methods of speed control of 3-O Induction motor. Explain the
principle of speed control of it by PWM method.
NOBLE GROUP OF INSTITUTIONS, JUNAGADH
FACULTY OF ENGINEERING,
DEPARTMENT OF ELECTRICAL ENGINEERING
Q.3
State the various points of comparisons and their choice/criterion for selection
between AC and DC drives.
Q.4
Draw the neat circuit diagram and explain the sped control of 3 phase Induction
motor by rotor resistance control method using chopper.
Q.5
Explain static Kramer drive and static Scherbius drive for slip power recovery
scheme for large size induction motor control.
Q.6
Discuss closed loop control of induction motor.
Q.7
A 400V, 4 pole, 50Hz, 3 phase, star connected induction motor has the following
parameters:
No. of stator turns/phase is twice the number of rotor turns/phase, r1=0.64 Ω, x1=1.1
Ω, r2=0.8 Ω, x2=0.12 Ω. The load torque is proportional to square of speed and is 40
N-m at 1440 rpm. If the motor speed is 1300 rpm, find (a) load torque (b) rotor
current (c) stator applied voltage. Neglect no load current.
Q.8
Q.9
Explain scalar control with reference to Closed-Loop control of induction motor
Explain v/f Control of three phase induction motor.
Q.10
Draw the torque speed characteristics of 3 phase Induction motor and explain the
following regions. (1).Plugging (2).Motoring (3).Generating.
CHAPTER - 5
Q.1
Explain the operation of a self controlled(closed loop) synchronous motor drive fed
from a cycloconverter to control the speed of synchronous motor with necessary
schematic diagram.
Q.2
Explain self controlled synchronous motor drive. How it can be implemented?
Q.3
Discuss volts/hertz control and self controlled synchronous motor drives with basic
schematic arrangements
Q.4
Explain Self-controlled Synchronous motor drive employing load commutated
Thyristor inverter.
Kishan Purohit
Subject In-Charge,
Electrical Engg. Department
NGI-Junagadh