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Department of Electrical Engineering
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Pre-University
Test : 19/04/2017
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6EE4A:
Advanced Power Electronics
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1
a)
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A single phase ac voltage controller has
resistive load of 10 Ω, input voltage Vs = 120 Volts, 60 Hz, the
delay angle of thyristor T1 is α
=
 . Determine
i)
RMS Value of output voltage
ii)
Input Power Factor
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RTU
2015
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8
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b)
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For 1
phase ac voltage regulator, develop a relation between conduction angle γ and
firing angle α,
and plot their variation as a function of load phase angle ϕ. Under what condition,
conduction angle γ becomes equal to Π.
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2014
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8
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OR
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1
a)
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For a single phase full wave controller with RL
load, draw the waveform of output voltage, output current and voltage across
thyristor. Determine the expression for rms output voltage.
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2010
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8
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b)
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An ac voltage controller has a resistive load of
R= 10 Ω.
The input voltage (rms) Vs= 10 Volts, 60 Hz. The thyristor switch
is ON for m= 25 cycles and OFF for n= 75 cycles. Determine:
i)
The rms output voltage V0
ii)
The input power factor (PF)
iii)
The average and rms current of thyristor.
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2013
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8
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2
a)
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Describe the working principle of single phase to
single phase step down cycloconverter continuous conduction for bridge type
cycloconverter.
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2015
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8
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b)
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What is load commutated cycloconverter. How does
it differ from line commutated cycloconverter?
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2013
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8
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OR
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2
a)
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A 3 phase cycloconverter feeds 1 phase load of
190 Volts, 45 Amps, at a power factor of 0.7 (lagging). Determine:
i)
The required supply voltage
ii)
Thyristor rating
iii)
Power factor of supply current.
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2013
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8
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b)
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Describe the control scheme for cycloconverter
using voltage sensing principle of converter group selection. Also draw
various voltage waveforms of a control scheme.
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2010,
2014
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8
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3
a)
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A single phase full bridge inverter is connected
to DC voltage source Vs. Resolve the output wave shape into
Fourier series (Harmonic Analysis)
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2015
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8
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b)
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State the need of reduction in Harmonics in
inverter. Outline the various methods for reduction in harmonics or the
improvement in wave shape.
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2013,
2014
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8
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OR
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3
a)
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Explain the working principle of 3 phase bridge
inverter with 180o of conduction.
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2015
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8
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b)
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A 3 phase bridge inverter is fed from 200 Volts
DC source. The inverter is operated in 180o conduction mode and is
supplying inductive, star connected loa with R= 10 Ω and L= 20m.H. The inverter
frequency is fo= 50 Hz. Calculate:
i)
Instantaneous line-to-line Voltage and Current
in form of Fourier Series.
ii)
Total Harmonic Distortion
iii)
Distortion Factor
iv)
Average and RMS Switch current.
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2014
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8
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4
a)
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Explain the working of L-type ZCS (Zero Current
Switching) resonant converter
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2015
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8
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b)
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Write down short notes on ZVS resonant converter.
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2015
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8
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OR
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4
a)
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Explain all the stages working of M-type ZCS
resonant converter.
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8
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b)
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Write down the advantage and limitations of ZVS
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2015
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8
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5
a)
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Write Short notes on
i)
Resonant AC Power supply
ii)
SMPS
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2014
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8
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b)
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With a neat sketch, explain Multistage
Conversion.
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2013
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8
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OR
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5
a)
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Discuss various control application (feedback
control or others) used in ac power supplies
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2014
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8
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b)
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What is switched Mode DC Power Supplies (SMPS).
Explain the working principle of flyback converter.
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2015
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8
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Department of Electrical Engineering
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Pre-University
Test : 15/04/2017
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8EE2A:
Electric Drives and their Control
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1
a)
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Explain the classifications of Load Torques.
Discuss their nature.
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8
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b)
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Explain Load Equalization in Drives with
necessary diagrams and derivatives.
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8
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OR
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1
a)
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A motor equipped with a flywheel is to supply a
load torque of 1000 N-m for 10 second followed by a light load period of 200
N-m long enough for the flywheel to regain its steady state speed. It is
desired to limit the motor torque to 700 N-m. What should be moment of
inertia of flywheel? Motor has the inertia of 10 Kg-m2. Its no
load speed is 500 rpm and slip at a torque of 500 N-m is 5%. Assume speed
torque characteristic of motor to be a straight line in the region of
interest.
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8
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b)
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What do you understand by Steady State Stability?
Discuss its main assumptions.
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8
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2
a)
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Explain the various methods of speed control of
DC Motors.
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8
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b)
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What are different types of braking methods used
in DC Motor? Discuss the differences
between each type of braking
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8
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OR
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2
a)
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A 200 Volts, 200 Amps, 800 rpm DC separately
excited motor has an armature resistance of 0.06 Ohms. The motor armature is
fed from variable voltage source with an internal resistance of 0.04 Ohms.
Calculate internal voltage of the variable voltage when the motor is
operating in regenerative braking at 80% of the rated motor torque and 600
rpm
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8
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b)
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A 200 Volts, 10.5 Amps, 2000 rpm Shunt motor has
the armature and field resistance of 0.5 Ohm and 400 Ohms resp. It drives a
load whose torque is constant at rated motor torque. Calculate speed if
source voltage drops to 175 Volts.
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8
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3
a)
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Discuss the A.C. Dynamic braking of Induction
motor drives
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8
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b)
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Discuss the various starting methods of three
phase Induction motors.
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8
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OR
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3
a)
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Discuss the voltage source inverter fed induction
motor drive operated in stepped wave inverter mode
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8
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b)
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A 400 Volts, star connected, 3 ph, 6 poles, 50 Hz
Induction motor has following parameter referred to stator: RS= R’r= 1
Ohm, Xs= X’r = 2 Ohms. For regenerative
operation of this motor, determine over-hauling torque it can hold and range
of speed for safe operation.
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8
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4
a)
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Explain the static Kramer’s drive for Induction
motor. Give its circuit diagram and
derivations.
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8
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b)
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Explain the Frequency control method of Induction
motor. How frequency can be controlled by power electronics devices
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8
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OR
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4
a)
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Explain the slip power recovery scheme with
static scherbius drive. Give the circuit diagram and derivation
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8
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b)
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Discuss the voltage source inverter control of
Induction motor
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8
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5
a)
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Explain the dynamic braking of synchronous motor
with VSI.
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8
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b)
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Discuss the operation of VSI fed self controlled
Synchronous motor drive
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8
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OR
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5
a)
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Explain the braking of Synchronous motor with
VSI. Draw the Speed-Torque characteristics of Regenerative braking
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8
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b)
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Explain the control of Synchronous motor with CSI
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8
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Attempt all questions.
Internal options are given in each question. All questions have been asked in previous
year RTU Papers
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