POWER SEMI CONDUCTOR DRIVE
Backlog management
Important questions
Prepare by: MAHESH YADAV.J
UNIT-1
1.
Explain 1-phase semi controlled converter of DC
separately excited motor operation with necessary wave forms and derive the
average output voltage.
2.
A) Explain 1-phase full controlled converter of
DC separately excited motor operation with necessary wave forms and derive the
average output voltage.
B) Explain about electric drive briefly, and what are its merits and demerits?
3. Derive the relation between
speed and torque of a single phase full wave converter feeding a separately
excited DC motor for continuous mode of operation and draw its speed- torque
characteristics.
4.
A 1 phase 230v 50hz supply feeds a separately
excited DC motor through two 1-phase semi converter one for field and another
for armature. The firing angle for field circuit is α=0 deg.
Field winding resistance
is 200Ω and armature resistance is 0.3Ω, the load torque is 50 N-M
At 900 rpm. The voltage
constant is 0.8 v/A-rad/s and torque
constant is 0.8 Nm/A2. Neglect the losses and assume current is
continuous. Find the following
a) The field current
b) The firing angle of semi converter in the
armature circuit.
b) The power factor of semi converters in the
armature circuit.
5. The speed of a 20 HP , 210V, 1000rpm
series motor is controlled by a 1-phase full converter. The combined field and armature resistance
is 0.25Ω, Kaf= 0.03 N-m/A2 and ,
Kres= 0.07V-S/rad. The supply voltage is 230V .
Assuming continuous and ripple free motor current. Determine the
following for firing angle α=30 0, and speed N=1000 rpm.
a) Motor
current
b)
Motor torque
c)
Supply power factor
Unit-2
1.
Explain the operation of three phase semi
converter connected to a separately excited DC motor. draw the necessary wave
forms for various firing angles.
2.
Explain the operation of three phase full
converter connected to a separately excited DC motor. Draw the necessary wave
formsfor various firing angles.
3.
Explain the operation of three phase full
converter connected to a DC series
motor. Draw the necessary wave forms for various firing angles.
4.
Derive the average output voltage of 3-phase
full converter and semiconverter.
5.
A 3 pulse converter controls the armature of
230V,1400rpm DC motor . the voltage drop in loop wires along with armature is
15V. find α at a speed of 600 rpm if the speed of motor at α=00 is
400 rpm at full load.
Unit-3
1.
Explain the single phase dual converter
operation briefly.
2.
A 220v, 1000rpm , 60 A separately excited DC
motor with armature resistance of 0.6Ω is fed from a circulating current dual
converter with ac source voltage ( line voltage) of165V. Determine converter
firing angles for the following operating points.
a)
Motoring operation at rated motor torque and 900
rpm
b)
Braking operation at rated motor torque at 900
rpm.
3.
Explain 3-phase dual converter..
4.
A) Explain about type of electrical breaking.
B) A 220v, 1000 rpm, 60 A separately
excited DC motor with armature resistance of 0.6Ω is fed from a circulating
current dual converter with ac source voltage (line voltage) of165V. Determine
converter firing angles for the following operating points.
A) Motoring operation at rated motor torque
and -900 rpm
b) Braking operation at rated motor torque at
-900 rpm.
Unit-4
1.
Explain about class E chopper drive or four
quadrant drive operation.
2.
Explain about close loop speed control of dc
drive.
3.
A. Explain operation of class A chopper fed
drive.
B.
Explain operation of forward motoring and
regenerative mode of separately excited DC drive.
4. A) Explain about dynamic
breaking with help of chopper circuit.
B) Explain about 2nd quadrant operation chopper fed dc drive.
UNIT-5
1.
A 3-phase ,4 pole ,50Hz induction motor has
rotor resistance of 0.25 ohm and stand still reactance of0.15 ohm. At full load
it operates at a slip of 3%. If the voltage is reduced to 60%, at what speed
will the motor operates with full load torque applied. (june-2014)
2.
a) Discuss briefly the various methods of
controlling the speed of the 3-phase induction motor from stator side using
solid state converters.
b) A 3-phase, 4
pole,50Hz, induction motor has rotor resistance of 0.2 ohm and stand still reactance of 0.1 ohm. At full load it
operates at a slip of 4%. If the voltage is reduced to 50%, at what speed will
the motor operates with full load torque applied..(November/December-2013)
b)draw the torque speed characteristics of the poly phase
induction motor . also explain the following operating regions.i)motor region
ii)generating region iii)breaking region.(December-2012)
4.for stator
voltage control scheme of a 3-phase induction motor discuss about speed range,
regeneration, harmonics, torque-pulsating, power factor,cost,efficiency and
applications(December-2012)
Unit-6
1.
a) Discuss in detail how the variable frequency
control of an induction motor can be achieved using voltage source inverter.
Mention the various advantages of the method.
b) In variable frequency control of
synchronous motor why (V/f) ratio is maintained constant up to base speed .Draw
the relevant characteristics..(November/December-2013)
2. Explain
a) Why the
variable frequency control of induction motor is more efficient than stator
voltage
control
b) why the variable frequency
control yields high torque to current ratio during starting
(May/june-2013)
3.a) describe
the performance of cycloconvertersdrives versus VSI for induction motor in
detail
and state their
advantages and disadvantages.
b)an inverter has to be rated in
apparent power rather than in real power. Explain why?
(December-2012)
4. explain
the principle of varying the speed of 3-phase induction motor by V/F method
discuss it for
a) operation below rated frequency
b) operation above rated frequency
5.for
variable frequency control of induction motor explain the following
a)for speed
below base speed V/F ratio is maintained constant. Why?
b)for speed
above the base speed the terminal voltage is maintained constant. Why?
c)discuss
merits and demerits of variable frequency control of induction motor.
6) the
parameters of three phase 400V,50Hz,6pole,960rpm, star connected induction
motor has the following parameters per phase referred to the stator.R1=0.3Ω,R2=0.1Ω,x1=x2=0.5Ω,Xm=20
Ω.
If the motor
is controlled by variable frequency control at constant flux of rated value,
determine the motor sprrd and the stator current at half the rated torque and
25Hz. (june-2014)
Unit-7
1)
Explain in detail about static scherbius
drive and static Kramer drive. (june-2014)
2)
a) Compare
the power flow diagram of a normal speed control method with that of slip power
recovery scheme for an induction motor.
b) Explain
about the static Kramer drive with a neat block diagram. also explain how to improve the power factor of static
Kramer drive..(November/December-2013)
3) a) in which way the SER can be made operable for both super
synchronous and subsynchronous
speed
control?
b) Discuss
briefly the traditional scherbius drive.
(May/june-2013)
4) a)compare the conventional
scherbius system with a scherbius drive.
b) What are the advantages of static rotor resistance control and
list the various applications.
(December-2012)
Unit-8
1)
With suitable circuit diagram explain the
principle of operation of current source inverter fed synchronous motor drive (june-2014)
2)
Explain the operation of load commutated CSI
fed synchronous motor drive. Draw the relevant waveforms.(November/December-2013)
3)
A) What is the basic difference between true
synchronous mode and self control mode for variable frequency control of
synchronous motor?
b) Draw the block diagram of closed
synchronous motor drive fed from VSI and explains.
(May/june-2013)
4)
A) Draw the block diagram of a closed loop
synchronous motor drive fed from VSI and explains the functioning.
b) Whatis the basic difference between true
synchronous mode and self control mode for variable frequency control of
synchronous motor?
(December-2012)
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