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Study material for SSE/JE examination by RRB on Electrical Engineering Part I

By on October 6, 2014

Storage Electric Battery

Battery is a device which converts stored chemical energy into electrical energy and vice versa. Faraday’s through his experiment has given two laws to govern the phenomenon of electrolysis. These are called Faraday’s Laws of Electrolysis.

Ist Law:    The mass of ions liberated at an electrode is directly proportional to the quantity of electricity passes through the electrolyte

IInd Law: The masses of ions of different substances liberated by the same quantity of electricity are proportional to the their chemical equivalent weights.

There are two types of batteries namely

Primary: Energy is stored in the composition of electrodes and when used, the electrode material undergoes an irreversible change. These are disposable type batteries and discarded when used. Applications are where usage is limited such as flashlights and other portable devices.

Secondary: these are rechargeable batteries which can charged and recharged multiple times ( theoretically infinite time but cycle is limited due to permanent damage of electrode)

Each cell has a positive terminal, or cathode,  and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to do work.

The common examples are (a) lead-acid batteries used in vehicles (b) lithium ion batteries used for portable electronics. Batteries come in many shapes and sizes, from miniature cells used to power hearing aids, blood sugar/ BP meters and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centres. Secondary Batteries are having wide range industrial application. In Indian Railways, the most important application is for train lighting and air conditioning of coaches.

Lead Acid battery

The main active materials required to build a lead-acid battery are

  1. Lead peroxide (PbO2), Positive Plate,  it is PbO2 when fully charged and converts to PbSO4 when discharged,
  2. Sponge lead (Pb), Negative Plate, it is Pb when fully charged and converts to PbSO4 when discharged
  3. Dilute sulfuric acid (H2SO4), electrolyte with specific gravity of 1.265 when fully charged and 1.120 when discharged. During discharge process, H2SO4 gets converted into water therefore, drop in specific gravity. The measure of the specific gravity is the best method of finding out the charge of the battery.
  4. The open-circuit voltage is 2.1 when fully charged and drops to 1.98 when fully discharged.
  5. High Specific gravity is used for specific application such as 1.3 (heavy cycle battery for traction application), 1.26 (automotive batteries), 1.25 (UPS and standby) and 1.215 (general purpose).
  6. High Specific gravity has the advantage of more capacity, less space, higher momentarily discharge rate but at the loss of shorter life.
  7. In general, lower temperature improves efficiency of electrical appliance. But for battery, it is the operating range of temperature to be maintained. Lower range reduces it capacity and higher reduces its life. Mobility of ion reduces at lower temperature, thus the reduced capacity.
  8. Rate of Charging current is important and depends upon temperature and state of charge.
  9. The specific gravity increases due to loss of water due to normal evaporation. It is important to maintain the water level.
  10. Batteries, when stored for a long period undergoes  capacity reduction due to the presence of generally irreversible side reactions that consume charge carriers without producing current. This is called internal self-discharge. A tickle charge is necessary to compensate for the internal self discharge.

In order to improve performance of battery, following development has taken place

  1. Use of sintered porous plug in which when the water evaporate, it travels through the porous sintered holes, and condensate thus saving loss of water and reducing maintenance need.
  2. Development of Vent Regulated Lead Acid/Maintenance Free Battery:  The most important advantage of VRLA battery is it ability to mount in any orientation, not requiring monitoring of electrolyte level etc. The term “maintenance free” could not succeed effectively.  VRLA batteries have been shown to reach catastrophic failure and are prone to thermal runaway. A common cause of failure is overheating and dust obstructing the valve, preventing release of gases. They are widely used in large portable electrical devices, off grid power systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like lithium ion.
  3. There are two primary types of VRLA batteries namely gel cells and AGM. Gel cells add silica dust to the electrolyte, forming a thick putty-like gel.   Absorbed Glass Mat (AGM) is fitted with fibreglass  mesh between the battery electrodes which serves to contain the electrolyte. Both designs offer advantages and disadvantages compared to conventional batteries, as well as each other.

Comparison of different other types of Batteries

Nickel Cadmium (NiCd) —The NiCd is used where long life, high discharge rate and cost advantage is important. Main applications are two-way radios, bio-medical equipment, professional cameras and power tools. The NiCd contains toxic metals and is environmentally unfriendly.

Nickel-Metal Hydride (NiMH) — It has a higher energy density compared to the NiCd at the expense of reduced cycle life. NiMH contains no toxic metals. Applications include mobile phones and laptop computers.

Lithium Ion (Li‑ion) — This is the fastest growing battery system. Li‑ion is used where high-energy density and lightweight is of prime importance. The technology is fragile and a protection circuit is required to assure safety. Applications include notebook computers and mobile phones.

Lithium Ion Polymer (Li‑ion polymer) — It offers the attributes of the Li-ion in ultra-slim geometry and simplified packaging. Main applications are mobile phones.

Capacity of Battery

The capacity of battery is given Ah say 100 or 200  Ampere.Hour and discharge rate like C10 or C20. A 100 Ah battery will deliver 10 A current for 10 hours before voltage threshold is achieved. A battery bank contains many cells of output voltage 2.1 V and therefore, a 24 V battery bank will contain 12 cells. Generally 12 or 24 V battery back is used for different application.

Back up time

It is important to know the calculation of back up time for emergency application. For this purpose, calculate the house hold load in Watts and  find out  diversity factory which is around 0.5 to 0.7. Select VA rating of inverter. VA rating is important as it is the current handling capacity of the inverter. Therefore VA ratings of inverter shall match with Watts*Pf of the load. Select inverter type which is Quasi Sine Wave, Square wave and Pure sine wave. Sine wave is best as it produces rotating field in the rotating machine of one speed resulting smooth running of motor like fan, Refrigerator, AC etc.

Select the battery bank of 12V than the back time will be

Back up time in Hours = (Ah)x(12V)x(PF)x(0.8η)/(Load VA) where efficiency of battery and inverter has to be taken into consideration.

More pages on this topic:

DC Motor (Page 3)

Pages: 1 2 3 4 5 6

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There Are 25 Comments

  1. Shashank says:

    Thanks a lot for this. Waiting eagerly for Mechanical and Civil too..

  2. Abhishek Bhardwaj says:

    Thank you Sir.
    Awaiting mech and civil….

    • Mahesh Kumar Jain says:

      Abhishek, I am a free lancer and feel happy in helping others with what little I know or I can do. all this material is not available readily with me. I am preparing, understanding and con-sizing to benefit you all. So first I have to complete electrical engineering which will take another week and than I proceed on other content. Please don’t depend on me alone for the content on other subject. I am not very sure if I will complete. However, I will be posting mock drill questions for you all shortly.

      • Sudhir Kamat says:

        Thanks a lot for your help sir.

      • vino says:

        thank u so much sir…from the starting i dont know where to start..but when i came to this site..i am getting ideas of where to start..thank u!!!

        • Mahesh Kumar Jain says:

          Thanks vino for the complement. I will request if you to share with your friends as well so that they are benefited. I am writing and posting study material and multiple choice questions to benefit candidates. Keep in touch with the website for new posts.

      • nitin says:

        Mahesh sir, your effort is very appreciable…i know sir its very difficult for you to focus on other mainstream as well…but sir plzz can we have any sort of guidelines regarding SSE rrb civil..any course material?? becuse syllabus is too wide in civil engineeing..
        if u could help sir..mail me at [email protected]

        very eager to hear from u…thank you

      • jagadeesh says:


  3. nitin says:

    everyone is posting for all other branches except civil engineering…can anyone help regarding course material for civil engineering..plzz mail me at [email protected]

    • Mahesh Kumar Jain says:

      I am an electrical engineer by profession and therefore posted the content of study material sufficient for objective type questions. I hope you know that you have to study electrical as well for civil engineering job exam as well.

  4. sumit butman says:

    Hell sir,
    I just know about you, that u help everyone for his carrier..
    So I need your help.
    (my education qualifications is- 10th passed under WBBSE, after that I am going to complete my diploma course in electrical engg in 2016,)
    I decide to sit in upcoming RRB’s ALP and JE exam..
    Will you please help me to complete the large GK syllabus, because I don’t know from where or which topic of gk comes in rrb exam, or is their any book for rrb’s gk preparation which is recently popular in market? This ‘gk’ is my problem to crack the exam.
    I am so asking because I forget every thing after learning, I like to read by understanding..

    I want make my carrier in Indian railway, pls help me..

    • Mahesh Kumar Jain says:

      It is good that you have decided to prepare on the subject now itself. At this stage, just do following things: 1. Read newspaper daily and makes notes of interested developments. There are many website making questions on the current affairs. Generally current affairs is given importance in any examination. 2. Read your class 8th maths and 9th-10th science books for fundamentals. Develop skills in multiplication tables. Prepare technical notes of your diploma classes which can fit in for multiple choice questions. I will be posting multiple choice questions mock drill tests for people like you to test in between your preparedness.

      • Sumit Burma says:

        Thank you sir,
        Thanks for advise…but according to new syllabus of RRB JE, not only from electrical trade but all trade’s question will be set in the technical part of question. Then my questions is that, how I prepare the other trades question?
        I mean the question will be set from Either all the 3 year’s syllabus of other trades Or only few important subjects of other trades.. Please help me sir.. I have no idea in it..

        If you have any recent RRB JE question paper then please attached it on your website..

        • Mahesh Kumar Jain says:

          The syllabus for JE and SSE as well as Assistant Loco Pilot is same irrespective of the branch he has done his ITI, diploma or Degree. The questions are generally such which one has studied of all the branches. For example while doing BE every one studies some part of the engineering of other branches also. I will be posting the question bank of RRB JE after some time.

  5. Sanket Sharma says:

    Mr.Mahesh Kumar jain could you please tell me which publication or author book is best for preparing RRB sse & je examination for technical & non-technical.

    • Mahesh Kumar Jain says:

      I don’t think any one book can be useful. I suggest you go through the Class IX and X books for JE Science, and Class XI and XII science books for SSE. Read and familiarize with the concept given Class VI and VIII arithmetic. For Technical part, go through your notes prepared during I and II year of study. For other subjects, many books are available. This should be more than sufficient.

  6. Rajesh says:

    hi sir, i would like to know the cutoff marks based on last year notification for SCR SSE & JE.
    And also the inhand salary of them.

    • Mahesh Kumar Jain says:

      I don’t have the cut off of SCR with me. But in any case, you should work of minimum 70% to ensure your making a place in the panel.

  7. Syed Faaique says:

    Sir what was the cut off marks for SSE under general category in 2014 for RRB Secunderabad.

  8. prasanna kumar semili says:

    sir plz can I have last 5 year question paper on following

    • Mahesh Kumar Jain says:

      The examination is not held every year. The question paper is not given to candidate after the examination. During the 2014 examination, the RRB has uploaded the paper on their website. The same are available on this website.

  9. kajal12 says:

    hello sir .. i m a b.e electrical passout. wantd help in tech sction of competative exams. pls help sir. or tell me if there is any you tube channel to help me.