Friday, 13 October 2017

Electrical Machines By D.P. Kothari and I.J. Nagrath

ABOUT THE AUTHORS
  • D P Kothari is presently Vice Chancellor of VIT University, Vellore. He obtained a BE (Electrical) in 1967, ME (Power Systems) in 1969 and PhD in 1975 from the Birla Institute of Technology and Science (BITS) Pilani, Rajasthan. From 1969 to 1977, he was involved in teaching and development of several courses at BITS Pilani. Prior to his assuming charge as Vice Chancellor of VIT University, Dr Kothari served as Director In-charge and Deputy Director (Administration) as well as Head Centre for Energy Studies at Indian Institute of Technology, Delhi; and as Principal,
  • Visvesvaraya Regional Engineering College, Nagpur. He was Visiting Professor at the Royal Melbourne Institute of Technology, Melbourne, Australia, during 1982–83 and 1989 for two years. He was NSF Fellow at Purdue University, US in 1992.
  • Dr Kothari, who is a recipient of the Most Active Researcher Award, has published and presented 625
  • research papers in various national as well as international journals, conferences, guided 30 PhD scholars and 63 MTech students, and authored 21 books in Power Systems and other allied areas. He has delivered several keynote addresses and invited lectures at both national and international conferences on Electric Energy Systems. He has also delivered 42 video lectures on science and technology on YouTube with a maximum of 35,000 hits!
  • Dr Kothari is a Fellow of the Indian National Academy of Engineering (FNAE), Fellow of Indian National Academy of Sciences [FNASc], Fellow of Institution of Engineers (FIE) and Senior Member, IEEE.
  • His many awards include the National Khosla award for Lifetime Achievements in Engineering for 2005 from IIT Roorkee. The University Grants Commission (UGC), Govt. of India, has bestowed the UGC National Swami Pranavananda Saraswati award for 2005 on Education for his outstanding scholarly contributions.
  • He is also a recipient of the Lifetime Achievement Award (2009) by the World Management Congress, New Delhi, for his contribution to the areas of educational planning and administration. His fields of specialization are Optimal Hydro-thermal Scheduling, Unit Commitment, Maintenance Scheduling, Energy Conservation (loss minimization and voltage control), Power Quality and Energy Systems Planning and Modelling.

  • I J Nagrath is Adjunct Professor, BITS Pilani, from where he retired in July 1999 as Professor of Electrical Engineering and Deputy Director. He is now actively engaged in writing books related to his long teaching and research experience. 
  • He obtained his BE with Honours in Electrical Engineering from Birla Engineering College in 1951 and MS from the University of Wisconsin, USA in 1956.
  • He has co-authored several successful books which include Electric Machines, 3/e, Modern Power System Analysis, Power System Engineering, Signals and Systems, Electrical Machines, Sigma Series and has authored Basic Electrical Engineering (all published by TMH). He has also co-authored Control System Engineering and authored Electronics: Analog and Digital. Besides he has these, published several research papers in prestigious national and international journals and continues to be active in studies and writing.
We are sharing only the link of this book which is already on internet. We respect copy right policy of  Electrical Machines edition - IV By D.P. KOTHARI and I.J. NAGRATH book publishers.


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Thursday, 5 October 2017

Electrical Machines edition - I By U.A. Bakshi V. U. Bakshi book pdf


Now you can read & learn electrical Machines first edition in offline. You can download  Electrical Machines By U.A. Bakshi V. U. Bakshi. This is a very nice book. All concepts of Machines are explained very clearly. You can get idea behind every concept in single read. You can use Electrical Machines edition - I By U.A. Bakshi V. U. Bakshi free download in doc format as text in image can be copied.

We are sharing only the link of this book which is already on internet. We respect copy right policy of  Electrical Machines edition - I By U.A. Bakshi and V. U. Bakshi book publishers.



CONTENTS:

  • D.C. Generators
  • D.C. Motors
  • Transformers
  • Performance of Transformers
  • Three phase induction Motors
  • Alternators
  • Single phase Motors
  • Electrical Instruments
  • Synchronous motors

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Thursday, 13 July 2017

Control Systems Engineering By LJ. NAGRATH and M. GOPAL in PDF Format


Now you can read & learn electrical Control systems engineering in offline. You can download  Contrl System By Lj. Nagrath and M.Gopal. This is a very nice book. All concepts of control systems are explained very clearly. You can get idea behind every concept in single read. You can use Control system by Lj. Nagrath and M.Gopal free download in doc format as text in image can be copied.

We are sharing only the link of this book which is already on internet. We respect copy right policy of  Control systems engineering by  Lj. Nagrath and M.Gopal book publishers.



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Thursday, 8 June 2017

OPERATION OF POWER SYSTEMS AND EQUIPMENT BY Juergen Schlabbach and Karl-Heinz Rofalski

Operation of Power Systems and equipment By Juergen Schlabbach and Karl-Heinz Rofalski PDF Free Download
OPERATION OF POWER SYSTEMS AND EQUIPMENT BY Juergen Schlabbach and Karl-Heinz Rofalski

Now you can read & learn electrical power systems and equipment in offline. You can download Operation of Power Systems and equipment By Juergen Schlabbach and Karl-Heinz Rofalski. This is a very nice book. All concepts of power systems are explained very clearly. You can get idea behind every power concept in single read. You can use Operation of power system and equipment by Juergen Schlabbach and Karl-Heinz Rofalski free download in doc format as text in image can be copied.

We are sharing only the link of this book which is already on internet. We respect copy right policy of operation of power system and equipment by Juergen Schlabbach and Karl-Heinz Rofalski book publishers.




CONTENTS:
  • Introduction 1
  • Power System Load 11
  • Planning Principles and Planning Criteria 23
  • Economic Consideration and Loss Evaluation
  • Topologies of Electrical Power Systems 45
  • Arrangement in Gridstations and Substations 69
  • Transformers 81
  • Cable Systems 111
  • Overhead Lines 137
  • Flexible AC Transmission Systems (FACTS) 159
  • Load-Flow and Short-Circuit Current Calculation 173
  • Connection of “Green-Energy” Generation to Power Systems 205
  • Protection of Equipment and Power System Installations 217
  • Overvoltages and Insulation Coordination 239
  • Infl uence of Neutral Earthing on Single-Phase Short-Circuit Currents 263
  • Tendering and Contracting 289
  • Appendix 321
  • References 325
  • Index 331
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Principles of Power Systems By V.K Mehta PDF Free Download

PRINCIPLE OF POWER SYSTEMS BY V.K. MEHTA

Now you can read & learn electrical power systems in offline. You can download Principles of Power Systems By V.K Mehta. This is a very nice book with attractive colors & amazing images. All concepts of power systems are explained very clearly. You can get idea behind every power concept in single read. You can use principle of power system by vk mehta free download in doc format as text in image can be copied.

We are sharing only the link of this book which is already on internet. We respect copy right policy of principle of power system by vk mehta book publishers.


CONTENTS:
  • Introduction 
  • Generating stations 
  • Variable load on power stations 
  • Economics power generation 
  • Tariff 
  • Power factor improvement 
  • Supply systems 
  • Mechanical design of overhead lines 
  • Electrical desing of overhead lines 
  • Performance of transmission lines 
  • Underground cables 
  • Distribution system general 
  • D.C Distribution 
  • A.C Distribution 
  • Voltage control 
  • Introduction to switchgear 
  • Symmetrical fault calculations 
  • Unsymmetrical fault calculations 
  • Circuit breakers 
  • Fuses 
  • Protective relays 
  • Protection of Alternators and transformers 
  • Protection of busbars and lines 
  • Protection againts overvoltages 
  • Substations 
  • Neutral Grounding




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Varactor diode Operation and Characteristics..

Operation of Varactor diode:
The varactor diode, also called a varicap, tuning or voltage variable capacitor diode, is also a junction diode with a small impurity dose at its junction, which has the useful property that its junction or transition capacitance is easily varied electronically.

When any diode is reverse biased, a depletion region is formed, as seen in fig 1. The larger the reverse bias applied across the diode, the width of the depletion layer "W" becomes wider. Conversely, by decreasing the reverse bias voltage, the depletion region becomes narrower. This depletion region is devoid of majority carriers and acts like insulator preventing conduction between the N and P regions of the diode, just like a dielectric between two plates of a capacitor.

As the capacitance is inversely proportional to the distance between the plates, the transition capacitance varies inversely with the reverse voltages. Consequently, an increase in reverse bias voltage will result in an increase in the depletion region width and a subsequent decrease in transition capacitance. At zero volt, the varactor depletion region is small and capacitance is large at  approximately 600pF. When the reverse bias voltage across the varactor diode is 15V ,the capacitance is 30pF.


Applications of Varactor diode :

  • Used in FM radio and TV receivers.
  • Used in AFC circuits,self adjusting bridge circuits and adjustable band pass filters.
  • Used in tuning of LC resonant circuit in microwave frequency multipliers and in very low noise microwave parametric amplifiers.

Tunnel or Esaki diode Operation and Characteristics:

Definition of Tunnel diode: 

This diode has two terminals. This tunnel diode is also known as Esaki diode. Here is the symbol of tunnel diode or Esaki diode.


The Tunnel or Esaki diode is a junction diode which exhibits negative resistance under low forward bias conditions. An ordinary PN junction diode has an impurity concentration of about 1 part in 10pow(8) with this amount of doping the width of the depletion layer is of an order of 5 microns. This potential barrier restrains the flow of carriers from majority carrier side to the minority carrier side. If the concentration of impurity atoms is greatly increased to the level of 1 part in 10pow(3),the device characteristics are completely changed. The width of the junction barrier varies inversely as the square root of the impurity concentration and therefore ,is reduced from 5 micron to less than 100Armstrongs.This thickness is about 1/50th of the wavelength of visible light. for such thin potential energy barriers ,the electrons will penetrate through the junction rather than surmounting them. This quantum mechanical behaviour is referred to as tunnelling and hence, these high-impurity-density PN junction devices are called tunnel diodes.

Characteristics of Tunnel diode:

       The V-I characteristic for a typical germanium tunnel diode is shown below. It is seen that at first current rises sharply as applied voltage is increased ,where it would have risen slowly for an ordinary PN junction diode(shown by dashed line). Also ,the reverse current is much larger for comparable back bias than in other diodes due to the thinness of the junction. The interesting portion of the characteristics starts at point A on the curve i.e. peak voltage.As the forward bias is increased beyond this point,the forward current drops and continues to drop until point B is reached. This is valley voltage. At B,the current starts to increase once again and does so very rapidly as bias is increased further. Beyond this point, characteristic resembles that of an ordinary diode. apart from peak voltage and valley voltage,the other two parameters normally used to specify the diode behaviour are at the peak current and the peak-to-valley current ratio,which are 2mA and 10nA respectively , as shown.  

The V-I characteristics of the tunnel diode illustrate that it exhibits dynamic resistance between A and B. Below figure shows energy level diagrams of the tunnel diode for three bias levels. The shaded areas show the energy states occupied by electrons in the valence band,whereas the cross-hatched regions represent energy states in the conduction band  occupied by the electrons. The levels of which the energy states are occupied by electrons on either side of the junctions are shown by dotted lines. When the bias is zero,these lines are at the same height. Unless energy is imparted to the electrons from some external source,the energy possessed by the electrons on the N-side of the junction is insufficient to permit them to climb over the junction barrier to reach the P-side. However ,quantum mechanics show that there is a finite probability for the electrons to tunnel through the junction to reach the other side,provided there are allowed empty states in the P-side of the junction at the same energy level. Hence the forward current is zero.

Operation of Tunnel diode:                  

            When the small forward bias is applied to the junction,the energy level of the  p-side is lower as compared with the N-side. As shown in figure 3, electrons in the conduction band of the N-side see empty energy level on the P-side. Hence, tunnelling from N-side to P-side takes place. Tunnelling on other directions is not possible because the valence band electrons on the P-side are now opposite to the forbidden gap in the N-side.

              When the forward bias is raised beyond this point,tunnelling decreases as shown in fig, 4. The energy of P-side is now decreased further , with the result that fewer conduction band electrons on the N-side are opposite to the unoccupied P-side energy levels. As the bias is raised,forward current drops. This corresponds to the negative resistance region of the diode characteristic. As the forward bias is raised still further,tunnelling stops altogether and it behaves as a normal PN junction diode.

Sunday, 19 March 2017

Explain the Parallel Operation Of Two Synchronous Generators or Alternators???

Parallel Operation Of Two Synchronous Generators or Alternators :

 The electricity demand of a country is fed by many alternators operating in parallel. There are various advantages of operating the alternators in parallel. some of them are listed below. 

  • For a given capacity of a generating station, either a single large unit or many small units may be installed. If there are many small units operating in parallel instead of the single large unit then a number of alternators operating at a time can be changed depending upon electricity requirements or load demands. This will in operating the alternator near its hill load capacity so that efficiency will also be better. Therefore operating cost will be significantly reduced compared to the single large unit.
*Principle and working of Synchronous generator or alternator : 
  • A particular unit may be shut down for certain period during the maintenance and inspection at the power stations. For that period the load can be transferred to other units if number of units are operating in parallel.
  • Several power stations are interconnected by a grid which is economical and advantageous. This will make sure the optimum utility of the alternators.
  • The continuity and reliability of the supply can be maintained at better level due to interconnections. 

There are certain requirements which must be met for parallel operation of alternators be reliable.
  • The rated speeds of the alternators should be such that they give same frequency generated voltage (f =PNs/120)
  • The output voltage rating of the alternators must be same. 
  • Even though the kVA ratings of the alternators are different, they should be of the same type so that waveform of generated voltage is same.
  • The armature of alternators should have reactance. 
  • The prime movers of the alternators should have same speed load drooping characteristics so that they can be loaded in proportion to their output ratings.

This conditions for proper synchronization of the alternators for the parallel operation to be successful are as given below. The alternator or group of alternators which are already in operation and sharing load are called running machines while the alternator which is to be connected to these alternators for parallel operation is called incoming machine. The incoming machine must meet the following conditions for proper parallel operation.

  • The terminal voltage of the incoming machine must be exactly same as that of the others or of the bus bars connecting them. 
  • The speed of the incoming machine must be such that its frequency if- PNs 120 equals the frequency of other machines or that of the bus bar. 
  • The phase of the incoming machine voltage must be same as that of the other machines or bus bar with respect to load. The phase voltages of incoming machine and bus bar should be in opposition which ensures that there is no circulating current between windings of alternators already in operation and the incoming machine. 

The interconnection of alternators i.e. the process of synchronization is already discussed previously. Now we will consider how the two alternators will operate parallel. What will happen if the driving torque or the excitation for any of the alternator is changed. In practice it is rare to have two alternators operating in parallel. But concept of parallel operation of alternators can be well understood by considering two alternators in parallel.

 Consider two identical alternators connected in parallel as shown in below figure.

Here cylindrical rotor alternators are assumed for simplicity,but the results obtained are equally applicable to both salient and non-salient machines.


Solving above two equations,

If no load is connected to the alternators only circulating current Isy will flow in the circuit.The current is given by


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