Dear Engineering Students,
I am Shankar, did my M.Tech in Power and Control from IIT Kanpur, B.Tech from JNTU Kakinada Campus and Diploma from Andhra Polytechnic Kakinada.
I worked in General Electric, Hyderabad for 6 years in the field of renewable energy sources. At present, delivering number of lectures in the field of power electronics (since 2007) and delivered lectures in Control systems as well (in the past) especially for GATE/ESE/PSUs. This blog is to explore the various opportunities for electrical engineering students especially preparing for competitive exams. I would like to utilize this blog as platform to share information as much as I can and requesting the continuous feed back for the improvement. I am maintaining this blog after my busy schedule as part of social service and giving back something to the society. If you like it, you can also be part of it

BNSS Shankar

Learning gives creativity, Creativity leads to thinking,Thinking provides knowledge, Knowledge makes you great
Always try to learn something from your actions
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Interview questions for MS and PhD in IIT Madras (2013-Dec)

Dear all,
One of my student Miss Madhuri from PM5A-GATE14 batch recently (1st week of Dec 2013) attended interview for admission into MS/PhD programme for power electronics in IIT Madras for Winter session 2013
I asked her to share one hour interview and written test questions with all of us

   Interview questions:
1.    If you are given a pure sinusoidal wave and a perfect DC is required from it. What is the circuit you will employ?
2.    Draw the most simple rectifier circuit you know
3.    Derive Load current equation for RL load in rectifier circuits using both Laplace transform and differential equations
4.    What is the most advanced PE equipment employed in motor drives as per your knowledge?
5.    Can a full wave bridge rectifier be used as an inverter? Can you use it without changing the source?
6.    How can you justify pulsating DC output you are getting out of rectifier can serve the purpose of rectification?
7.    What is the physical form inverter we are using in homes?
8.    What happens if an inductor of small value if connected to the source given in VSI?
9.    Even though DC motors have efficient speed control capabilities, we are using Induction motors for most of the applications. Why?
10.    Why supply frequency is only 50 or 60 HZ?
11.    Why not diode bridge circuit cannot be used as an inverter?
12.    Draw the waveforms for RL load in VSI circuits?
13.    Draw the waveform for RC load? Will you use RC load parallel combination or series combination? Explain in detail
14.    What happens if 10A rms, current source is given to LC parallel circuit where intial stored energies in L and C are zero?
15.    What are the practical applications of KCL, KVL and ohms laws?
16.    Is there any particular situation in circuit, ohm’s law cannot be applicable?
17.    What is the need of cyclo converters?
18.    Explain everything you know about three phase cyclo converter by drawing as much as waveforms you can draw. (Note: Professor in the panel asked her to draw waveforms on board…She realized the pain I am having daily in my class….I am kidding… I am enjoying daily in work)
19.    If we are happy with half wave rectifier circuits, why full wave rectifier circuits are invented?
20.    What are the typical ratings of SCR?
21.    Do you know about Matrix converter?
22.    Tell me the practical applications of PE you have seen? (My 3 hours introduction class is the answer for this question)
23.    What is DC transformer?
24.    Will PE equipment affect the stability of any machine employed in electric drives?
25.    What is the resistance between primary and secondary windings of the transformer?
26.    Why only semiconductor devices in PE circuits will operate as switches?
27.    Do you know anything about secondary breakdown of BJT?
28.    What happened if mechanical switches are used in place of SCRs in converters?
29.    Finally why do you want to join in power electronics why not in power systems in M.S/M.Tech?

Written test questions:
1.    Explain SCR characteristics as bipolar and unidirectional switch?
2.    A single phase full converter input is sinusoidal voltage. And load current is 4 A of constant. Find ripple factor in output voltage, fundamental rms source current, fundamental power factor, THD. Derive all the equations used
3.    Explain with derivations, how to find active power, pf when voltage and current are having harmonics
4.    A constant DC voltage source is connected to and RL draw load through a diode. Draw current and voltage across all components. Derive all the equations
One important question: Finally, one of the professors in panel asked her “Who is your PE faculty and where did you learn power electronics
As she answered all the questions, interview panel appreciated her understanding in the subject

I wish her all the best and I am very much satisfied about her performance and as her PE teacher

Thank you Madhuri

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