gate prep statergies...
Power Systems : The widest subject Hi Guys, Today I am here with a post that all of you have been waiting for as to how to study Power Systems. In my personal opinion this is a subject which has the widest course and different topics have different flavors like the approach in Fault Analysis is entirely different from the approach in Transmission Lines. Here, i will give only the insights as to what you should study for each topic and then we have released K-Notes for quick revision of Power Systems and Kuestion to illustrate the problem solving techniques that i will be talking about here. The major topics in Power Systems can be listed as follows:
Transmission and Distribution o The first topic under this unit is overhead transmission lines and in this topic first you need to memorize the expressions for Inductance and Capacitance for both Single Phase and Three Phase Lines. So you should practice some problems based on this which involve the computation of GMD and GMR. o The next topic that you should cover is modelling of Short and Medium Transmission Lines as Long Transmission Lines is not much important in Steady State Analysis and Short Transmission Line is most important. Here you should also focus on the A,B,C,D Parameters of the line and the power expressions in terms of A,B,C,D and remember the approximate voltage regulation in Short Transmission Line which is same as Transformer. o The next topic under this unit is Surges and in that topic you need to memorize the thevenin equivalent circuit for analysis of surges and by that you can easily calculate the Transmission and Reflection Coefficient for Voltage and the coefficients for currents are not important. o The other important topic is Voltage Control and Power Factor Correction and both these concepts for Numericals involve a single approach which will be better illustrated in kuestion but these two concepts are important as you can expect one of either two topics in GATE exam. o The next topic is UG Cables and in UG Cables there are two important concepts, one is the insulation resistance and other is the capacitance model for 3 phase 3 core belted cable which has core capacitance and sheath capacitance but question is rare from this topic. o The other small topic under this unit is Overhead Insulator where only a single problem based on voltage distribution across different discs can be asked and that you can easily derive using KCL or remember the expression upto 3 discs. o The last topic is the Distribution Systems which also has a single type of problem which involves just applying KVL and finding the currents in different branches.
Load Flow Studies o In this unit you need to study about construction of Bus Admittance Matrix and you can leave out the algorithm for construction of Bus Impedance Matrix.
But we need to study the fault Analysis by the use of Bus Impedance Matrix which involves knowing that diagonal elements of the matrix represent thevenin impedances at different buses. The next thing that we need to remember is the order of Jacobian Matrix in Newton-Raphson Load Flow Solution. Also, there are some simple question where we need to find voltages and their angles at different buses and those are the simplest questions as they just involve using KVL between different buses and using power expression for Short Transmission Line and this point will be more illustrated in Kuestion.
Economic Load Dispatch o In this topic you just need to study about the transmission loss coefficients and penalty factor and then how to distribute load across various generating units based on Incremental Cost and Penalty Factor.
Fault Analysis o Here we need to study about Symmetrical and Unsymmetrical faults and first thing in case of Symmetrical faults is the transient and steady state component of fault current and there you just need to memorize a single expression by which you can easily derive the maximum momentary current as well. o Then in symmetrical fault analysis you need to solve problems where we find the symmetrical SC currents by drawing the equivalent circuits and also problems where we need to calculate the current limiting reactance. One thing that you need to take care about is units as the answer may be given in pu or in ohms so you need to take care else you can mark the incorrect answer. o The last thing about symmetrical faults is calculating the ratings of Circuit Breakers based on Symmetrical fault Analysis like Momentary Current, Breaking Current and Making Current. o Before going to Unsymmetrical Fault Analysis you need to study about Symmetrical Components which involves just a small transformation matrix and about Sequence Networks in which zero sequence network for Transformers in most important and can be asked directly in exam. This is explained in detail in K-Notes for Power Systems which will be up soon. o In case of Unsymmetrical Fault Analysis we need to remember the equivalent circuits for all three types of faults LG, LL and LLG Faults and how to calculate fault current from sequence components.
Power System Stability o This is the smallest topic in Power Systems but still it is very important. Here Steady State Stability is not Important but transient stability is and you need to remember the two inertia constants "H" and "M" for that and the swing equation. o The next thing is that you need to remember the equivalent M and H when there are two machines which are swinging coherently or in-coherently. o The last and most important topic is the equal area criteria for calculating the critical clearing angle and i would recommend that you understand the method involved instead of memorizing the expressions involved as that will reduce the chances of error.
Power System Protection o This is most rarely asked topic and is widest of all the units but now since exams are happening in multiple sessions so we can expect one question at least in one of the sets. o The only numerical part in this unit is concentrated around Plug Setting Multiplier(PSM) and the differential relay so you need to be clear on both the aspects and practice a few problems based on these two concepts. o Other than that for theoretical purposes you can remember the usage of some general relays like Distance Relays types and which type is used where and also the types of relays used in Transformers like Buchholz Relay.
So guys this is the entire power system in a nutshell. Hope you all benefit from it and to make it a bit easier we have released K-Notes and Kuestions for Power Systems on our website so check it out: http://www.kreatryx.com/
Wednesday, 3 December 2014 Digital Electronics: The most scoring subject Hi Guys, The next subject in our K-Plan is Digital Electronics and to explain you how to go about this subject we have with us Kuldeep Kaushik who cleared GATE-2014 with AIR-6 and is very enthusiastic to help out the GATE Aspirants. So here is what he has to offer for Digital Electronics: Digital Electronics is considered to be the simplest subject of all, and yes it is. This subject has full potential to fetch you 100% marks from this area provided you give it required practice . Let us take it topicwise. Logic Gates Start from basics. practice truth tables of all gates and make logic circuits for functions. Try to minimize number of gates to implement given function. Refer Morris Mano for this part. Study about 3 input Ex-OR and Ex-NOR gate and also study NAND and NOR implementation of all gates. Minimization Techniques Boolean Algebraic rules are too simple. Do practice K-Map as it is very essential topic. All Digital Electronic revolves around it. So first you need to clear basics of minterms and maxterms. How things unfolds if we loop zeroes in K-Map? We can invert a function using KMap. So simply make fool proof command over it. You will require it in counters also. Quine Maccluskey method is not important. For practice go to Kanodia, Morris Mano and coaching booklets.
Basic concepts regarding adders, subtractors and comparator should be studied. Remember carry and output expression of this to make things easy as sometimes they may ask “which combinational ckt this calculated expression represent?”. Multiplexer is very important. A function can be implemented by 4 selector switch MUX, 3 selector switch MUX and even with 2 selector switch with different input combination. Practice K map thoroughly to make command over MUX. Emphasis should be given to understand the internal logic circuit of MUX, Encoder, Decoder etc. The book from Tocci Widmer is good to cover this topic. Sequential Circuits Tough Part of Digital Electronics!!! No friends, it is not tough in real. This zone is ready to give away marks provided you have enough practice and yes NO DOUBTS!!!! Enter in this zone after mastering combinational circuit because you know we will add memory to make combinational Circuit sequential. S-R, D, T and JK flip flop are core of this chapter. These flip flops have specific input combinations for which output is don't care so make concepts clear pertaining to that. Always solve questions by making present state- next state table of flip flop, you should not use its characteristic equation directly as it involves looping of don’t cares which may provide you with wrong solution and be sure it will be one of the option in Exam. Practice how to convert one flip flop in other. Synchronous counters, ripple counter, johnson counter all are easy. Design these counters by hand. Don’t think why to design for objective paper. It will be helpful. Let me assure you. Make table of which type of counter affect frequency of input in which way. Practice how to calculate MOD number of given counter. Lock-out phenomenon is important. Master Slave relay is also imp. Keep concepts clear regarding Race around condition. I recommend Tocci Widmer for this part. Logic Family Question are rare from this part in gate, but bad luck will knock the door without any warning. So prepare this part also. Learn how transistor make logic circuits. We can implement every function with diode and transistors. Remember some standard representations. Remember some theoretical points like which family has highest fanout, lowest noise margin etc. With this I end my description of study pattern for Digital Electronics. Thumb Rule for GATE is Area where you have doubt , believe next exam will have question from there. I wish you all the best. Do honest efforts and rest leave to God. I wish you pass with flying colors. So guys, if you find this post helpful please share it with your friends and colleagues. In case you feel there is not enough time left for GATE exam, I would recommend that you follow Koncept 2016 instead of Standard Text Books. Click on the link below to know more, https://www.kreatryx.com/plan-and-pricing#tab2 About the Author: Kuldeep Kaushik graduated from SKIT, Jaipur in Electrical Engineering. He secured 6th rank in GATE-2014 during his final year of graduation. He got selected for IISc Bangalore, GAIL, NTPC, IOCL. He is currently working in GAIL India Ltd. as Senior Engineer. Posted by ankit goyal at 12:11 18 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: books, digital, GATE-2015, IES, Online, recommended, Subject Tips
Sunday, 9 November 2014 A measured approach towards Measurement Hi Guys, I am back with a new Subject Related post and this time we will deal with a subject that most of the Electrical Engineers neglect and do not give the due importance. The one mistake that everyone does is not realizing that this subject has got a good weight-age of around 6-8 marks in the GATE exam. So guys my first recommendation will be to not neglect this subject as this is narrow and easy as well so spare at least one week for its preparation also. The books that can be referred for this subject are "Electrical Measurement and Instrumentation by AK Sawhney" but i still would not recommend using a book as that book is very vast and still if you want to read the book then you can better highlight the topics that need to be read from each chapter. This subject includes the following topics:
Measurement and Error o This chapter includes basic error analysis in terms of Guaranteed Accuracy Error, Limiting Errors for various arithmetic operations like addition, subtraction etc and also errors in terms of Standard Deviations so here this much is sufficient and no need to study the Standards of Length and time as those are not required for GATE.
Electro-mechanical Instruments o This is the most important topic from this subject. o The basic principle of instruments and the expressions for deflecting torque in various instruments like PMMC, Moving Iron and Dynamometer type Instruments is the most important topic in this chapter. o Always remember that PMMC measures average value of output and other two measure the RMS values. o The applications of PMMC like ammeter, voltmeter and rectifier type instruments are also important and range extension of these instruments is the most important using Shunt and Series Resistances. o In Dynamometer the most important application is the wattmeter and for that you need to be clear with the three phase circuits phasor diagram as if you know the phasors well then you do need to remember any formulas and you can easily crack the non standard cases as well. Also remember the formula for calculating the power factor angle in case of two wattmeter method as that is most commonly asked. o Energy meter is the next important instrument and here the only important concept is the error in reading and that can be computed using the energy constant, other than that the working principle and other things are not that important from GATE perspective. o Electrostatic and Thermal instruments are not that important but try to remember the expressions for deflecting torques for both these instruments.
Instrument Transformers o The current Transformer is important from here though not many questions are asked but this is relatively simple as we just need to study about the ration and phase angle error and since the equivalent circuit is same as the Transformers from Electrical Machines this can be easily understood.
Bridges o The Inductance and Capacitance Measurement come under the AC Bridges and these are very simple as they are just based on a simple phenomenon that product of impedances in opposite branches are equal. This concept can be applied to simple bridges like Maxwell,s Inductance Bridge, Maxwell's LC Bridge and Owen's Bridge but still expressions must be remembered for Hay's Bridge and Anderson's Bridge as they are not that easy to derive. o The Capacitance Measurement bridges include De Sauty and Schering Bridge and those are also simple but one thing must be remembered in all bridges is the circuit of each bridge against its name. o The last is Wien Bridge Oscillator for measurement of Frequency.
Measurement of Resistance o Wheatstone Bridge is the most important from this topic and mostly questions are based on the condition when bridge is unbalanced and we need to find the voltage across the detector. o Other methods include Kelvin's Double Bridge, Voltmeter-Ammeter Method, Ohmmeter, Carey-Foster Slide Wire Bridge.
Cathode Ray Oscilloscope (CRO) o This is second most important topic from this subject. o The first and most important thing in this topic is to remember the purpose of each and every part in the functionality of CRO like Horizontal Deflection Plates, Vertical Deflection Plates etc. o The other important thing is the Lissajous Figure and calculating ration of frequency of x and y signal from the figure, calculating phase difference between the signals.
Digital Meters o In this topic all type of ADC must be studied but they are also covered under Digital Electronics and other than that parameters of Digital Instruments like Resolution etc must be studied and those are more important but this topic is not very important from GATE perspective.
The K-Notes for this topic are already up on the website here: K-Notes for Measurement So guys, since this subject has good weightage and is small also so do complete this subject and score as much as you can in this subject. Also, if you find the article helpful please share it with your friens and do comment with your queries. Posted by ankit goyal at 12:24 9 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: books, GATE, GATE-2015, notes, Offline, Online, Subject Tips
Friday, 31 October 2014 Power Electronics: Nightmare for Electrical Engineers Hi Guys, After many Electrical Engineers requesting for a post on Power Electronics, finally we are here with a post on How to tackle Power Electronics for GATE in a most efficient way. This subject is a kind of nightmare for most Electrical Engineers including myself and so i was looking to get you guys an expert who handled this subject exceptionally well. So, this time we have with us Santhosh Kumar Pabbineedi who appreared for GATE-2014 and secured an AIR-141 and has been guiding young GATE Aspirants ever since. So guys, here is what he has convey to you guys regarding Power Electronics: Now a days I am able to see a few seniors who got good rank in GATE-14 guiding future aspirants. Most of the people attend coaching in various coaching institutes which a act as a bridge between students and textbooks. As they explain not only the concepts but also the exception cases for every concept with which it is easy to answer a question. This method works in almost all cases, for an example in Power Electronics , in case of rectifier with Rload for any firing angle we never get negative average output. You will not find this direct statement in any text book but it is pretty much used while solving problems. 99% of the people never solve unsolved exercises of any text book which are very important. Now I will explain you how to get good grip on Power Electronics.
First of all be clear with the fact that in power electronics we have to deal with a few concepts only. It has pretty less syllabus as compared to other subjects and has got good weightage. In this study plan I strictly suggest you to own the following text books. PS Bimbhra , Rashid and Power Electronics pdf notes which is available in NPTEL website. Power Electronic Devices: For Basic operation of various devices follow Bimbhra as their operating characteristics are well explained in it. I still remember the diode problems one must solve before going to thyristor circuits are there in front pages of Bimbhra & they will explain you how a thyristor will work if it gets a continues gate signal or no gate signal. In a page range 30-70 of Bimbhra you will observe that there were some direct gate questions based on diode. Phase Controlled Converters: For rectifiers. Bimbhra is more than sufficient and one must be cautious about Fourier analysis of every rectifier. Understand the difference between ripple-free load and normal load. 90% of questions will be based on ripple-free load and in that case if you have all the formulae on finger tips , you can fetch maximum marks. Coming to battery charging problems in rectifiers go through the NPTEL notes & few problems are also there in text book. Choppers: For Choppers. Dont Follow Bimbhra . I will explain you why. In case of problems which need attention towards inductor operation. More than the mere formulas we need basic
concepts to answer the question. In GATE-14 first session there was a question on ripple current in some chopper , the formula mentioned in Bimbhra is (Vs/(4fL)) , if you apply this you will get an answer but its wrong. In a article I cannot tell you the reason but it must be solved by using basic kirchoff law , which is well explained in Rashid. In Rashid you will find KVL approach to solve almost all equations which I feel very interesting and straight forward but for Fourier analysis follow Bimbhra. Inverters and Commutation: For Inverters and Commutation circuits Bimbhra is good. For Inverters also the Fourier analysis is important. Operation is well explained in that and most of the questions are repetitive in nature in gate. Small concepts like PWM methods might be confusing but at maximum you need 5 hours to get a grip on them. There are various methods to solve a single question in inverters which you'll know by practising . Cyclo Converters and AC Voltage Regulators: Cyclo-Converters & AC voltage regulator are a combination of Rectifers and Inverters and very less questions will be asked in that area. For those who feel Power Electronics as tough. 10-12 Days of first time preparation and two revisions i suggest you before giving gate. Practice as many as problems. Go for discussions. While solving a problem you may see some option as fitting your calculations and you may be tempted to go for it to save time but please do not do that. In 2 to 3 days i will upload my handwritten notes on Power Electronics which has all concepts covered in 10 pages so please keep checking this page for more updates: Santosh Handwriiten Notes Download Happy Studying and Best of Luck for Preparation. So, guys if you found this post helpful for your GATE preparation please share this with your friends and also comment with your queries. For latest GATE Study Material and new products for last 3 months preparation please visit this link: K-Notes, Kuestions, K-Plan About the Author: VSK Santhosh Kumar Pabbineedi passed out in 2012 and obtained AIR-141 in GATE-2014 without any coaching. He studied while working parallel till last November . He was selected for PowerGrid, IOCL, HSL, BARC , HPCL ,NHPC but failed in MDL. He is presently working in PGCIL.
Posted by ankit goyal at 14:18 38 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: books, GATE, GATE-2015, recommended, Subject Tips, textbook
Monday, 20 October 2014 Analog Electronics for ECE
Hi Guys, As per the request from many ECE guys for a post regarding Analog Electronics important topics, I am writing this post for them. This post is actually from Rohit Jain who himself is one of the GATE Toppers from ECE. He obtained AIR-15 in GATE-2012. Analog is one of the most important subject for ECE and also since it is a core subject so it becomes much more important that this subject be covered in detail. But many GATE Aspirants are often confused as to what specifically we need to study from this subject as this subject is very vast in itself. So, to reduce the effort we need to target the topics that are specific to GATE and these are the topics that are recommended by Rohit Jain for Analog Electronics for ECE: Diode: Rectifiers (Half wave, Full wave and Centre tapped) – ripple frequency, ripple factor, PIV, rectification efficiency, TUF ( Transformer Utilisation Factor ), conduction angle, DC current, Thevenin equivalent circuit, comparison of three ( half, full and centre tapped) | Peak detector – surge current | Clipper – positive, negative, two level | Clamper – positive, negative, voltage doubler Transistors: BJT theory – CB, CC and CE configuration – Input-ouput and transfer characteristics | Early effect | Eber’s Moll model | Active, Cut-off, Saturation and Reverse Active mode | Concept of ICO, ICBO, ICEO | Biasing and Stabilization – CB biased, Self biased, Diode compensation, Thermistor and Sensitor compensation | Voltage regulation – Line variation, Load regulation, Zener ckt, BJT ckt, IC ckt | Current Mirror | Miller’s theorem |Small signal analysis - Hybrid Model, Approximated hybrid model, Pi – Model, T – Model, re model | High frequency analysis – Unity gain frequency (fT), fβ, fα | FETs - Small signal model – expression for Id, gain,| Biasing – self bias, drain-gate biasing
Amplifiers: Cascaded amplifiers – fH, fL, Bandwidth formulas | Darlington pair - super β transistor, biasing problem, bootstrap | RC coupled amplifier – Frequency response | Cascoded amplifiers | Direct coupled amplifiers | Emitter coupled differential amplifier | Tuned amplifier | Feedback: Basics | Different configuration – voltage amplifier, current amplifier, transconductance amplifier, transresistance amplifier | Desensitivity | Current and voltage sampling, Voltage and current mixing Oscillators: Barkhausen criteria | Audio Frequency oscillator – RC, Wein bridge and Phase shift | Radio Frequency oscillator – Hartley, Colpitt, Clapp, Crystal | Figure of merit and Frequency stability criteria Power amplifiers: Thermal runaway – concept, expression | Harmonic distortion | Class A, B, AB and C amplifiers – advantages, disadvantages, area of operation, cross over distortion, efficiency | Push-pull amplifiers OP-AMP: Basic theory – properties, Slew rate, CMRR, Offset voltage and current, Biasing voltage and current, Transfer characteristics | Ideal and Practical Op-amp | Different
configurations – Inverting, Non-inverting, Summer, Integrator, Differentiator, Log and Antilog amplifier, Voltage follower | Current to voltage converter and vice versa | Filters – Lowpass, Highpass, Allpass, Bandpass, Bandstop, Butterworth | Frequency response – cutoff frequency | Schmitt trigger – Hysterisis loop | Precision rectifiers Multivibrators: Bistable, Astable and monostable vibrators using BJT, Op-amp and 555 timer IC – time period derivation, calculation of stable state current and voltage, transition time About the Author: Rohit Jain obtained AIR-15 in GATE-2012 and obtained AIR-2 in ESE-2012. He has worked in CSC and NTPC and after clearing IES-2012, he is presently working in ITS. Posted by ankit goyal at 18:31 11 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: analog, GATE, Subject Tips, textbook
Thursday, 16 October 2014 Analog Circuits: An uphill battle for Electrical Engineers Hi Guys, Thanks for appreciating the effort that we put in and thanks for being patient for the next post so here I am with a new subject related post and this time it won't be me that will be guiding you but rather another GATE Topper, Arpit Srivastava (AIR-7, GATE-2014 EE). This time we'll be dealing with the most daunting topic for Electrical Engineers "Analog Circuits" as rarely Electrical Engineers are interested in this topic. But still it is one of the most important subject for GATE exam and you must fully prepared to tackle it. So let us see what Arpit has to say about Analog Electronics. Analog circuit has its roots in electronics generally electrical people used to leave this topic. It seems very hard subject. But by learning few topics you can overcome apprehension of this subject. As far as gate is concerned, there is no need of through out knowledge of Electronics Devices. Electrical engineers can leave Electronic Devices for gate but basic working principles of devices (Diode, BJT, MOSFET, FET) are necessary. You need to know about various terminals and direction of current Flow and applied terminal voltage for different modes of operation. The following topics are included in Analog Circuits:
Diodes Circuits o It is very important topic for Gate exam. Clipper should be practiced thoroughly. You can practice various Diode circuits from kanodia book and any reference book.Thermal effect on Diode can be left as it is an unimportant topic. Also general circuits where we need to judge the state of multiple diodes in a single circuit is important and should be practiced.
Biasing and amplifiers o You should know about biasing concepts like finding the Q-Point or Operating point in a circuit for the purpose of DC Analysis. After learning biasing, concept of amplifier is important. There are many models to solve amplifier problems. But re model is simple to learn. In GATE exam they ask question only from this model. Also you may be asked about different components in the small signal model like Trans-conductance etc and these parameters can be directly from the DC Analysis. o By practicing some question you can master it. BJT amplifier are more important than FET and MOSFET.
Power Amplifier o For Electrical GATE paper you need not worry about this topic and it can be left out.
Feedback Amplifier o In gate exam detailed questions are not asked in this topic. But you should be aware about various topology and its effect on output and input impedances, gain, noise, distortion.You can leave cascade amplifer for GATE exam.
Operational amplifier o Concept of Operational Amplifer starts with differential amplifier and its various definition like CMRR, slew rate input biasing current etc. Out of these CMRR and slew rate is important. o Most of the questions are asked from basic op amp topology. You can solve them by just applying network theory and mostly centered around the concept of Virtual Ground. These are simple and mostly asked in gate exam. You should also be aware of various Filter Designs as well as they can asked in Control Systems or Network Theory as well. o Also, you should be clear with analysis of Schmitt Trigger as that is one of the most important topic in GATE.
555 Timer o This is not very much important for electrical guys.
Overall you can score 3 to 6 marks in this subject easily but just studying few topic. diode and op amp circuit are most simple and important part of this ocean size subject. So guys Analog Electronics is not as daunting from inside as it looks from the outside. About The Author: Arpit Srivastava graduated from MITS Gwalior in 2014 in EE Stream and cleared GATE with AIR-7 in 2014. At present he is working in IOCL as an Operation Officer. So if you guys wish to get in touch with him regarding your preparation do let us know. Also please share this article with your friends who are also fussing about Analog Electronics so that these misconceptions can be cleared soon. You can download K-Notes and Kuestions for GATE Preparation on our website: Download K-Notes here
Also guys, keep giving us your valuable feedback so that we can keep improving our products and keep helping you to crack GATE. Posted by ankit goyal at 21:22 29 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: analog, books, GATE-2015, Offline, Online, Subject Tips
Sunday, 24 August 2014 Electrical Machines Demystified Hi Guys, I sincerely hope that your preparation is on track. In this post I will discuss on how to tackle the most important subject of Electrical Engineering which is Electrical Machines and believe me when I say that by the end of this post you will understand how to cover the machines course in the least possible time. Electrical Machines is the most important topic for Electrical Engineers not only from GATE perspective but also for understanding as you are not a complete Electrical Engineer unless you have a good grasp of Machines concepts. In GATE exam if they focus on core subjects then Machines will easily have weight-age of more than 10 marks. The problem with machines is not the complexity of concepts but rather the impact of the problem on one's mind. People usually presume that machines' question would be tough and this presumption is based on the language of the question generally which is more complex than the question itself. First we will cover each topic and the concepts required for GATE from that topic and then I will tell you some problem solving tips: Transformers The important concepts from GATE perspective are equivalent circuit of Transformer and the concepts of Voltage Regulation and efficiency. Generally the biggest confusion in the Voltage Regulation Concepts is whether it should be calculated with respect to No-load Voltage or Full-Load Voltage, I would suggest that you calculate both as either of them may be used and you mark the option based on that but if question is numerical type we generally calculate with respect to rated voltage. Also, one of the most commonly asked concepts is the core losses which are Hysteresis and Eddy Current Losses so practice few problems on that where we are given total core losses and we need to calculate individual Hysteresis and Eddy Current Losses. In case of three phase transformers, if you can understand the phasor diagrams and naming then it is very good else you can leave that as question is very rarely asked but you need to practice numericals based on three phase transformers. The next concept is the autotransformer which I believe is the easiest as entire question just depends on the ratio of low voltage to high voltage rating of auto-transformer and we can scale each and every quantity of two winding transformer based on that. So totally we have to remember 4-5 concepts for Transformers. DC Machines This Chapter totally revolves around 4 equations which are two performance equations one each for generator and motor and the expressions for Torque and EMF. The most commonly
asked questions are based on speed control of DC Motor and we must always remember that whenever we want to calculate speed we need to calculate the back emf and then take the ratio of two emfs to compute the ratio of two speeds. But the complication arise when this question is based on DC Drives and either the speed is controlled via rectifier or an chopper so for that you need to remember the final expression for each type of rectifier and also buck-converter and if you can do that then the problem is merely reduced to playing along with 4-5 equations. But most probably since drives is not mentioned in this year's course will not be asked in GATE exam so you can leave such problems. Synchronous Machines The first concept in this chapter that you need to remember is the pitch factor and distribution factor as sometimes questions may be asked on the ratio of emfs induced when a 3-phase winding is re-wounded as a single phase and the ratio of KVA Rating of the two winding. Also we must remember the concept of Armature Reaction that whether this effect is magnetizing, de-magnetizing or cross-magnetizing based on the power factor at which the machine operates. The next concept is that of Synchronous Impedance that comes from Open Circuit Characteristics and Short Circuit Characteristics. Other than that this chapter is mostly based on two equations which are Power-Angle Equation and the emf-terminal voltage relation which comes from equivalent circuit of the machine and you need to solve these two equation to calculate any parameter that is asked. Sometimes, question may be asked based on the torque angle of a Salient-Pole Machine so we need to remember a direct formula for that and the last concept is power-factor correction using Synchronous Motor.
Induction Machines This is the only machine whose functioning you need to understand well as mostly the questions are based upon the concept of slip and for that you need to understand various things like speed of rotor and speed of rotor magnetic field and stuff like that. The new concept that is now a days appearing and is non-trivial is the concept of Inverted Induction Motor where supply is connected to the rotor and stator terminals are connected to load there also you need to understand the speeds of all field and rotor speed also. Equivalent Circuit is not much important here.Probably the most important concept in this chapter is the torque-slip characteristics and conditions for maximum toque and starting torque and question may be based on ratio of these. Also remember the formulas for Air-Gap Power and rotor copper loss. The last concept is the starting of Induction Motor by Auto-Transformer or Star-Delta Starter which you need to study. This is the topic from which will have highest weight-age among all machines. Important Note Please understand the power-flow diagram for each machine as that will be used for calculating efficiency and the concepts for Single Phase Induction Motor and other special Machines are not much important but you can remember the step size for stepper motor. Problem-Solving Tips Practice more and more problem to develop the skill where while reading the problem you will easily understand the equations that will be involved while solving the problems. Also before solving any problem you need to devote 30 seconds to carefully read and understand
the problem as most of the time mistake is committed due to not reading the question properly. If you want concise yet sufficiently detailed study material for GATE preparation, click on the link below: https://www.kreatryx.com/plan-and-pricing#tab2 Also, last year's most successful program for GATE last month's revision Krash 2016 will be launched soon. Click on the link below to know more: https://www.kreatryx.com/gate-courses#krash If you like the article please share it with your friends and let me know how was the article in comments and do revert to me with comments in case you have any query. Posted by ankit goyal at 09:02 32 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: AIR-1, Ankit Goyal, books, GATE, GATE-2015, GATE-2016, IES, machines, Online, power, Subject Tips
Monday, 28 July 2014 How to Study Control Systems? Hi Guys, Control Systems is one of the most important subject for both Electrical as well as Communication engineers from GATE point of view. The weight-age of Control Systems has been consistent over the years at around 8-10 marks surpassing many core subjects of both branches itself. The problems that appear in GATE from this topic are based on application of concepts instead of directly asking a theory concept.So, while preparing Control Systems, the focus must be on solving a lot of problems. Also, there are numerous interesting real life applications of Control Systems which make this topic all the more wonderful. Around us we see many systems operating in our everyday life and we can treat every system as a control system though it may be manual or automatic. Even human body itself can be treated as a control system with brain acting as controller or processor and co-coordinating the actions of different body parts based on response delivered to the brain by different senses. Thus by seeing the practical applications of this subject you can be much more involved and can easily generate interest which you may otherwise lack. So the key to this kind of subject is to learn practical applications side by side or else these subjects can become very monotonous. The standard book that you can follow for this subject is Automatic Control Systems by B.C. Kuo. It has been well written with numerous practical application of concepts given. Now I will treat this subject topic by topic and will try to highlight the relevant and irrelevant portions in each topic so that you can concentrate more on relevant topics instead of getting lost in the vastness of standard books. The following topics are included in GATE curriculum: • Transfer Functions Basically in this topic we need to learn about Block Diagram Reduction Technique and simple equivalent Transfer Functions for both positive and negative feedback. This topic is very basic
and very much necessary as all advanced topics lay their foundation here and strong foundations are the core of every successful student. Next thing that comes in this topic is Signal Flow Graphs and Mason's Gain Formula as these concepts may sometimes simplify the effort if you have to calculate equivalent transfer function as block diagram technique may sometimes be very lengthy. Almost every year one question from SFG is guaranteed so do prepare this topic well. • Time Domain Analysis This topic is basically very easy and mostly formula based as we need to learn the formulas for various time domain parameters like Rise Time, Maximum Overshoot, Settling Time, Peak Time and also various error coefficients like Position Error Coefficient, Velocity Error Coefficient and Acceleration Error Coefficient but remember as per GATE we are asked to compute the actuating error instead of error between output and input. So, error coefficients can be used directly for non-unity feedback systems as well. • Stability This topic is very simple and the only concept that needs to be studied here is the Routh Stability Criterion and also keep in mind the special cases for Routh Criterion. The special cases include when the entire row goes to zero or the first element of the row is zero. The questions from this topic are very rare but understanding of stability criteria is must to have general understanding. As these basic concepts can help you understand the behavior of many systems. • Root-Locus Technique In this topic basically we need to learn about drawing root-locus and general properties associated with it like number of asymptotes, angle of asymptotes, centroid, break-away and break-in points. The one most important point to remember is the change in root-locus properties when positive feedback is applied instead of negative feedback there we have to understand about the Complimentary Root Locus. From past 3-4 years every year a question from this topic is being asked. • Frequency Domain Analysis In this topic many small formulas like Resonant Frequency, Resonant Peak and Bandwidth are important. Apart from that the concept of Nyquist Criterion is important and here we need to learn small Nyquist Plots for simple function and how do they change once you add zeroes and poles. If you can draw Nyquist Plot you may directly be able to judge the stability of the system. The other concepts that can be frequently seen in GATE exam from this topic is Gain and Phase Margin. The last topic that is covered here and is most relevant for GATE exam is Bode Plots and here you need to learn how to draw asymptotic Bode Plots and slope of each asymptote. Also, you need to practice finding transfer functions from a given Bode Plot. • State-Space Analysis This topic mostly contains concepts that we study in Linear Algebra but we need to learn about State Transition Matrix and its relation with Transfer Function and also the solution of State Space Equation by the use of State Transition Matrix. The concepts of Controllability and Observability are also very important and you must judge these aspects of a Control System by the use of Controllability and Observability Matrices. You can expect a question from this topic every year in GATE exam. • Compensators
Here we just need to learn the condition for maximum phase shift for both Lead and Lag Compensators and also electrical circuit implementation of both. Those who do not wish to be lost in Standard Books and want to study only what is really relevant for GATE can take a look at our courses: https://www.kreatryx.com/plan-and-pricing So, these are the topics that I feel are relevant for GATE in Control Systems and if you feel that I have missed something you can mention it in the comments. Was this article helpful to you? If so, please share it with your friends and colleagues so that they can also benefit. Posted by ankit goyal at 01:17 13 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: AIR-1, Ankit Goyal, books, control, GATE, GATE Topper, GATE-2016, IES, IISc, Offline, Online, recommended, Subject Tips, textbook
Tuesday, 8 July 2014 How to Study Signals and Systems? Hi Guys, As I told we will be uploading Subject based tips before every subject in K-Plan for EE so we shall be dealing with Signals and Systems first as to what all topics are important and how to approach each of these topics. If you haven't yet gone through the K-Plan then first have a look at it by clicking on the link below: http://blog.kreatryx.com/2015/07/k-plan-for-gate-2016-ee.html Signals and Systems is one of the most important topics in both EEE and ECE GATE exams as it always has a consistently good weightage and also because of simple and very less number of topics in Signals and Systems, this can easily be converted to one of the most scoring topics in GATE. Also the problems from Signals and Systems are not very much tricky and mostly all are straight forward. The best way to prepare for Signals and Systems is to filter out the necessary information and make very short notes which can include properties of Transforms and other formulas that help in Problem Solving. The most important thing to take care while preparing Signals and Systems is to solve a large number of problems that will teach you a number of tricks regarding GATE problems. For Problem Solving you can refer Oppenheim and Wilsky book. Otherwise, you can try solving our Question Bank in Koncept 2016 which has good problems that too fully solved, Click on link below to purchase Koncept 2016: https://www.kreatryx.com/plan-and-pricing#tab2
Now coming to the topics that are covered in Signals and Systems, the following topics constitute Signals and Systems curriculum:
Continuous and Discrete Time Signals
This topic is not very important for GATE and we just need to study here the impact of shifting and scaling operations on the waveform of the signals, it may be continuous and
discrete and you can easily find several examples of these sort of operations on signals in Oppenheim book. One more thing that is covered here is the classifications of signals based on different criteria like: o o o
Periodic and Aperiodic Signal Even and Odd Signal Power and Energy Signals
So the classification criterion needs to be carefully studied as it is a small concept but can be directly asked.
Linear Time Invariant Systems
This probably is the most important part in Signals and Systems as all the systems are studied here only and the most important concept here is that of impulse response and Convolution. The impulse response is useful when there is a connection of more than one systems may be in cascade configuration or parallel one but we need to remember what will be the equivalent impulse response of entire system. Also convolution methodology needs to be remembered though one can argue that we can take some transform like Laplace Transform and multiply two such transforms and take the inverse to find the output of the system and thus avoiding the convolution altogether but reality is that this process is time consuming and by the help of convolution we can compute output at some points only and verify with the options given and save time. The next important thing the properties of Systems like Causality, Time-Invariance, Stability, Linearity and we need to study the criterion to determine each of these properties for a system because many times we may be given a system and asked which of these properties does that particular system exhibit.
Basically there are two types of Fourier Series and Transforms as one exists for Continuous Time Signals and other for Discrete Time Signals and both are very similar but for EEE GATE course discrete time Fourier Series is not included and hence they only need to prepare only continuous time fourier series. The approach towards preparing any transform and any series is to have two pronged approach that is you need to remember two things or rather three things which are: o o o
Analysis and Synthesis Equations Properties of Transforms Common Transform Pairs
The thing with the GATE exam is most of the questions are directly based upon the properties of transforms and if you will calculate them completely, a lot of time will be wasted and if you apply some property, it may be done in a short time but to apply properties you need to remember some transform pairs so that you can represent a signal in terms of some known signal and apply a property, so try to prepare all the transforms in this fashion only.
Here also the approach remains same and we just need to remember that Fourier Transform exists for Aperiodic Signals and Fourier Series for Periodic Signals and Fourier Transform approaches Fourier Series for periodic Signals. Also there is one very important duality that a signal discrete in one domain is periodic in other and vice versa so a periodic signal in time domain is discrete in frequency domain which means fourier series exists as fourier series exists only for periodic signals and that too provided Drichlet Conditions are satisfied. Also, one more important thing is the fourier transform of rectangular and triangular functions and the converse also which can easily be computed by duality property.
Laplace Transforms only exist for Continuous Time signals and is the most important transform as it is used in Engineering Mathematics and Control Systems as well and the only additional thing that comes here is the concept of Region of Convergence (ROC) as the same transform may have different inverses based on different ROCs. So please remember no Laplace Transform is complete without ROC and rest of the approach remains same as we need to follow three pronged approach. One more thing that is introduced here is the concept of Initial Value and Final Value Theorem and one must always remember that final value only exists subject to the condition that the system is stable and sometime students may be fooled by this, so before applying final value theorem, please verify the stability.
Z-Transform is the analogue of Fourier Transform but for the discrete time signals and hence the properties are very similar but there are some striking differences also like in case of Final Value Theorem so such differences must be clearly remembered but rest of the things and even concept of ROC remains the same. One thing to be noticed in Laplace and Z Transform is the concept of Stability and Causality as sometimes that may come in handy if pole-zero plot is given and system properties need to be identified.
The only important concept in Sampling is for the Nyquist Rate and Nyquist Frequency and you must practice drawing one or two waveforms where sampling frequency is less than Nyquist Frequency and that will result in aliasing as sometimes waveforms may also be asked and you may come across many weird kind of problems , please ignore them as they are not important for GATE but please also read about Band-Pass Sampling Theorem as that may also be asked. So guys, I believe that if you follow whatever I wrote above then all topics will be covered without much pain and effort and also it will be easy to remember as this is most confusing subject but at the same time most scoring one. So, please let me know if this post was helpful in you shortlisting the topics that need to be studied and if so please share it with your friends and let me know the queries and responses in comments. If you feel the need of classes to understand the concepts then I would suggest that you try out our free demo plan of Kapsule which is a complete GATE online preparation portal, Here
you would find demo content for Signals and Systems and Control Systems. Click on link below to register for free: https://www.kreatryx.com/plan-and-pricing Posted by ankit goyal at 16:01 28 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: GATE, IES, mathematics, Offline, Online, recommended, Subject Tips, textbook
Monday, 16 June 2014 How to Study Network Theory? Part-2 Hi Guys, I hope that last post helped you in developing your preparation strategy for Network Theory, this post is in continuation to the last post and is targeted towards the topics that are a part of EE curriculum but not included in ECE curriculum. The following topics will be covered in this post: · Three Phase Circuits Three Phase Circuits come more naturally to EE guys as they have to deal with three-phase circuits in Electrical Machines and Power Systems, so in Network Theory only the basics of those are covered and the thing to be remembered is the relationships between Phase and Line quantities (Voltage and Current) for both Star and Delta Connections. These relationships are very handy as they can be used directly for balanced 3-phase circuits and unbalanced circuits will be solved completely step-by-step as there are no direct relations but the questions from this topic are very rare. · Electric and Magnetic Fields The question from this topic is quite common and the most important thing in this topic is to remember the “Maxwell’s Equations” in differential form for both Electric and Magnetic Fields as sometimes you may be asked to verify whether a given function can represent a Magnetic Field or an Electric Field. Also the concepts covered in Class-XII like Ampere’s Law, Gauss’s Law in integral form should also be remembered and some formulae for Electrical potential and Fields due to standard charge distributions should be remembered. Also since Maxwell’s Equations use the concepts of Divergence and Curl so you must try to remember the formulas for these in Cartesian, Cylindrical and Spherical Co-ordinates, though it may not be used but it is always better to be safe than sorry. So, guys this concludes our discussion about Network Theory and please comment if you have any specific doubts about any of these topics. And please keep visiting our website for free online content which will be uploaded soon: http://www.kreatryx.com/ Posted by ankit goyal at 11:40 1 comment: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: Subject Tips
Monday, 2 June 2014 How to study Network Theory? Part-1
Hello Dear Readers, Thanks for following my blog closely and I apologize for not putting up this post soon enough and to keep you waiting. So, here I am with the next post in the series of subject-wise posts on preparation tips and here I will provide some topic wise important concepts that are most essential for GATE exam. Network Theory is one of the most consistent subjects in EC and EE GATE papers and mostly the problems are not very much tricky but rather simple and hence it becomes a scoring topic and so mistakes must be avoided as they can have immense negative impact on your GATE Score. What I have observed during my preparation twice is that un-necessary information is provided in most of the coaching institute’s modules which is not at all important for GATE exam. Most of the topics in EC and EE curriculum for the Network Theory is same except the Three Phase Circuits and field theory which are additional topics in EE curriculum. This post can be very lengthy and hence I have divided it into two parts : the first part containing the common topics and second for additional topics in EE curriculum. Network Theory is a problem-based subject where mostly practicing the problems is much more important than reading the theory and hence for studying the concepts any book can be followed or else you can download pdf notes from NPTEL and lastly you can download short notes for Network Theory from our below mentioned website and the notes will be uploaded soon as short notes are helpful at the final stages of the preparation. www.kreatryx.com For Problem Solving, I believe GATE Electrical or GATE EC by RK Kanodia is sufficient and the problems are same in both. The following topics are part of Network Theory:
The questions from this topic in GATE are very rare but still this topic should be prepared for the sake of completeness. Here small topics are very much important like the number of trees possible for a given network but the concepts like Incidence, Cut-Set and Tie-Set Matrix are not very much important but still should be once looked at as there is no harm. Also, different terminology should be remembered like twigs, links etc.
The solution methods listed are Nodal and Mesh Analysis and the usage as to where to use which method is something that you will get by practice as using the appropriate method will lessen the effort and save you a lot of valuable time.
For GATE, the names of theorems are not very much important but for IES they can come in handy for Objective Paper. So, it is better to remember the name and usage of theorems and the most important theorems are Thevenin and Norton Theorem as sometimes the equivalent circuit can be directly asked, other than that theorems like Superposition, Tellegen’s theorem are not very important. Here, Star-Delta Transformation is important as it can be used with other subjects as like Electrical guys can use the same for Transient Stability Analysis for Fault away from line ends in Power Systems and Maximum Power Transfer Theorem is also important but there is
one trick involved there as well as maximum power to load can be when internal resistance is zero if allowed, so that case must also be verified.
Steady-State Sinusoidal Analysis
The most important concept under this topic is the concept of Phasors which I believe comes more naturally for Electrical guys as they encounter Phasors more often in Electrical Machines and Power Systems. This is important as it reduces the effort immensely for solving an AC Network and also for this topic, you need to learn to use the calculator in Complex mode and do calculations in Phasor terms as that will ease the calculations and make them more accurate. The concept of Resonance is also very important under this topic and the key to that is just to equate the imaginary part of Impedance and Admittance to zero based on the case under consideration.
The transient response for general circuits like RC and RL circuits should be directly remembered in terms of initial and final conditions as that will save you a lot of time and can be used many places else like Chopper circuits in Power Electronics for EE Guys. Other than that there is not much but you should always try to solve one or two problems completely by forming the differential equations and solving them so that you can always handle the nonstandard cases.
Circuit Analysis using Laplace Transform
This topic is important as this comes in handy even for Control Systems also and here the important thing to remember is to include the initial conditions in the models for Inductor and Capacitor in the s-domain and also you need to remember some common Laplace Transforms which you may do anyways in Signals and Systems.
State Equations for Networks
The important thing to learn in this topic is to define the state variables as sometimes you may define more than required and even this topic is common with the Control Systems.
Here the important parameters are Z-parameters, Y-parameters, H-parameters and Transmission Parameters and you need to memorize the conditions for Symmetry and Reciprocity in terms of various parameters. Also, one more thing is important here as to what parameters are added or multiplied for different network configurations like Cascaded Connection, Parallel Connection and others. To find these parameters you just need to remember the Network Equations for various parameters and then decide which quantity should be equated to zero to find a particular parameter which avoids the need to memorize the formulas for these parameters. Please comment for any queries related to this post. To be Continued……. Posted by ankit goyal at 08:35 24 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest
Labels: Subject Tips
Monday, 12 May 2014 How to Study Engineering Mathematics for GATE? Hello Readers, From now on, i will be sharing the subject-wise preparation tips, so the first subject that we'll be taking up in this post is Engineering Mathematics. Engineering Mathematics is very much relevant to the GATE exam as the weight-age given to this subject is consistent over the years whereas other subjects may not be that consistent. Every year you can find the weight-age of this subject to be 8 to 10 Marks. Engineering Mathematics is a subject that has a very wide course as this course during the college days is covered in 4 to 5 semesters and to prepare it completely at one time is overwhelming. So the key to prepare for such subjects is to keep short notes handy with you or maybe you can have a sort of Formula Sheet so that you can look up to a concept whenever you need it.
Linear Algebra o While preparing for Linear Algebra, focus must be on Eigenvalue Problems and also the Matrix algebra as almost every-time there will be a question from either of these two topics. One must also remember the properties of eigenvalues like the relation between eigenvalues of two matrices which are inverse of each other and other similar properties.No need to get involved in the basis vectors and span of basis vectors to form an n-dimensional space as those concepts are absolutely unnecessary for GATE. Calculus o For single variable calculus there are not many problems except the maxima and minima problems and the most important topic is vector calculus involving Gradient, Divergence and Curl and Vector Integral Theorems (Green's, Gauss's and Stokes Theorem) as there are lot many properties of each concept and you must remember all those to solve the problems faster like divergence of curl is always zero, believe me that these properties do come-in handy in the exam. Differential Equations o There are not many concepts in the differential equations as you can always check the solution by satisfying each option in the differential equation given in the problem statement but at the same time do remembersome special differential equations like Bernoulli's Equation and Euler Differential Equation. Complex Functions o It is smallest topic among all topics from Engineering Mathematics and the only important concepts are Cauchy-Riemann Equations for Analytic Functions and Residue Method of Integration and rest of the topics are not necessary for GATE. Probability and Statistics o The general problems involving Probability can be prepped up by practice and there is no need to study much about them but you can always remember
Baye's Theorem, more focus should be on Random Variables like Poisson's Distribution and other distributions. Statistics is also very important and you must remember mean,median and mode concepts as well as coefficient of corelation, so do make short notes for each of these concepts Numerical Methods o Two things are important in this section one is the equation solving by methods like Newton-Raphson and Bisection Method and other is the Numerical Integration technique by methods like Trapezoidal Rule and Simpson's rule so do mug up the formulas for each of these methods and make good use of Calculator like you can form equations in form of answer of previous step so that recursion becomes faster and more accurate.
So basically the key to tackle such a large subject is to narrow down the course content to the most relevant topics and cut-out the unnecessary topics otherwise your workload will increase but not your performance. If you guys are looking for short notes on each subject, please keep following our website as we are preparing the same and will upload soon. The link to our website is: www.kreatryx.com So so keep yourself updated with latest uploads on the website. Please comment with any other queries and what next subject should we take up. Posted by ankit goyal at 11:12 26 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Labels: Subject Tips Older Posts Home Subscribe to: Posts (Atom)