Hall Ticket No Question Paper Code: BPE001
INSTITUTE OF AERONAUTICAL ENGINEERING
(Autonomous)
M.Tech I Semester End Examinations (Supplementary) July, 2017
Regulation: IARE-R16
POWER ELECTRONIC CONTROL OF AC DRIVES
(Power Electronics and Electric Drives)
Time: 3 Hours Max Marks: 70
Answer ONE Question from each Unit
All Questions Carry Equal Marks
All parts of the question must be answered in one place only
UNIT I
1. Draw and explain the power circuit of a single phase semi converter feeding a separately excited dc
motor. Explain with typical voltage and current waveforms the operation in continuous armature
current.
A 200V, 875RPM, 150A Separately excited DC motor has armature circuit resistance and inductance
of 0:06
. The motor is controlled by a single phase fully controlled rectifier with source
voltage of 220V, 50 Hz. For continuous conduction operation calculate
i. firing angle for rated motor torque and 750RPM
ii. firing angle for rated motor torque and -500RPM
2. Draw and explain the power circuit of a single phase fully controlled converter feeding a separately
excited dc motor. Explain with typical voltage and current waveforms the operation in
discontinuous conduction.
The speed of a 10HP, 210V, 1000RPM separately excited dc motor is controlled by a single phase
full converter. The rated motor armature current is 30 A and armature resistance is 0:25
.
The ac supply voltage is 230V. The motor voltage constant is 0.172V/RPM. Assume that
sufficient inductance is present in the armature circuit to make the motor current continuous and
ripple free. For a firing angle 450 and rated motor current determine
i. The motor torque
ii. The speed of the motor
UNIT II
3. Explain the principle of operation of dual converter control of separately excited DC motor in
simultaneous current control method.
A 220V, 750RPM, 200A separately excited DC motor has an armature resistance of 0.05
.
Armature is fed from a three phase dual converter with circulating current control. The A.C
source voltage is 400V(Line). When motor operates in forward motoring converter A works as
a rectifier and B as an inverter. Calculate firing angles of converters A B for the following
operating points for the following assuming continuous conduction.
i. Motoring operation at rated torque and -600RPM
ii. Regenerative braking operation at rated torque and 600RPM
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4. Explain the principle of operation of a three phase full wave controlled bridge rectifier with R-L
load and ideal supply with neat circuit diagram and waveforms.
Discus the principle of operation of a three phase fully controlled converter control of separately
excited d.c motor.
UNIT III
5. Draw the block diagram of a DC motor drive and derive the transfer function of the following subsystems.

i. DC motor and load
ii. Converter
iii. Current and speed controller
iv. Current feedback
v. Speed feedback
6. Draw the block diagram for the closed loop control of the two quadrant DC motor drive with
field weakening using a phase controlled converter and explain the speed control below and above
the rated speed.
Explain the control modeling of the three phase fully controlled converter.
UNIT IV
7. Explain in detail about chopper with regenerative capability with circuit diagram.
Describe the principle of operation of a two quadrant chopper with neat circuit diagram and
necessary waveforms.
8. Explain the methods of hysteresis control and PWM control for controlling current in DC motor
drives.
UNIT V
9. Describe the methods of hysteresis control and PWM control for controlling current in DC motor
drives.
10. Draw the flowchart for the dynamic simulation of the chopper controlled dc motor drive and explain
the dynamic performance of a chopper controlled separately excited dc motor drive for a step command
in speed reference, in normalized units with necessary wave forms.