Download Model Paper-Industrial Elecronics

IESL COLLEGE OF ENGINEERING
ADVANCED DIPLOMA LEVEL-STAGE 1-2013
ME 3004 - INDUSTRIAL ELECTRONICS
MODEL PAPER
Q1.
(a) Describe the operations of SCR, DIAC and TRIAC with the help of their I-V
characteristic curves.
(b)
D1
iL
RL
RE
vin
vC
U1
C
R
S1
RG
Figure-Q1
In the circuit shown in Figure-Q1, U1 UJT provides a trigger operation to the SCR S1.
Assume the drop across the SCR is negligible. Further, 𝑣𝑖𝑛 is sinusoidal with 20𝑉 𝑟𝑚𝑠
and 𝑅𝐿 = 20Ω.
i.
ii.
Explain the operation of the circuit with the help of waveforms of 𝑣𝑖𝑛 , 𝑣𝐶 and
𝑖𝐿 .
What is the maximum possible power that can be delivered to the load?
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Q2.
Consider a power diode in a forward biased arrangement connected in series with a
supply 𝑉𝑠 , resister 𝑅, capacitor 𝐶 and an inductor 𝐿.
(a) Derive a differential equation whose solutions are the current through the series
combination.
(b) Hence find the characteristic equation of this circuit.
(c) Discuss the three damping conditions in this circuit.
(d) What is a freewheeling diode?
Q3.
(a)
(b)
(c)
(d)
Draw the block diagram to illustrate the general structure of a motor drive.
Explain why motor drives are important in domestic and industrial applications.
Differentiate high performing motor drives and low performing motor drives.
A separately excited dc motor is running at constant field flux. The load torque on the
motor is proportional to the speed. When the speed is at 𝜔𝑚 the supply power is
disconnected suddenly. Derive an expression for the speed as a function of time, after the
power disconnection.
Q4.
(a) What is the main advantage of the induction motor drives compared to dc motor drives?
(b) Using a suitable equivalent circuit and a phasor diagram for three-phase induction motor,
obtain the expressions for the air gap flux Φ𝑎𝑔 .
𝑉
(c) Hence explain the principle of 𝑓 control for the induction motors.
𝑉
(d) State why 𝑓 control is not suitable for the low speed applications.
Q5.
(a) Write short notes on the following.
a. MOSFET
b. IGBT
c. SIT
d. COOLMOS
(b) Completely explain the operation of a three phase star rectifier. (Use suitable circuit
diagrams)
(c) Compare the performance of the three phase star rectifiers to that of three phase bridge
rectifiers.
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Q6.
(a) Compare the linear regulators to the switch mode regulators highlighting advantages and
disadvantages.
(b) What are the steps taken in linear regulators to minimize its drawbacks?
(c) Completely explain the circuit operation of a voltage controlled 3 phase PWM inverter.
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