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

By on October 6, 2014

DC Motor

dcmtor

Image taken from Hyper Physics

DC motor works on application of DC power supply. Working principle of DC motor and generator is shown. The current in left and right end of the coil is opposite to each other but magnetic field is perpendicular for both the parts of the coil. As the direction of flow is opposite, the force produced is also opposite which results in torque acting on the coil. The coil starts rotating and keep on reducing when it moves to the top, the torque is zero at the top and again start increasing. The reversal of current is required in the conductor after half rotating to keep the torque in one direction for which commutator and brushes  are provided.

There are three types of DC motor namely, Shunt Motor, Compound Motor and Series Motor. In earlier days, before the advent of AC induction motor, Shunt and Compound motors were used for constant speed motors. The most important advantage of DC series motor is its ability to produce large starting torque and making it suitable for an application which requires high starting torque such as traction, hoist etc. This application was widely used till the advent of electronics drives to get the similar characteristics from induction motor.

The standard equations of DC motors areScreenshot - 06-10-2014 , 17_13_51

From this,  following interpretation emerges to be remembered are

Shunt and Compound DC Motor: In these motors, the field and armature is connected in parallel to the applied voltage. Speed is directly proportional to voltage. Torque is proportional to armature current. These motors found wide application in 20th century for all fixed speed application and almost constant torque. But with the development of three phase induction motor, application of this motor is now obsolete.

Series Motor: The field is connected in series to the armature and field is current is regulated by insertion of permanent and speed regulation field diverter.  Speed is inversely proportional to flux and during start if does not have a mechanical load, the speed will shot up. The DC series motor therefore, always starts on load. Torque is  proportional to square of the armature current before saturation. Series motor has wide applications for traction, crane, hoists etc. But now with the development of solid state technology to derive similar characteristics from Induction motor, series motor is also now obsolete except for maintenance for the life cycle of the motors in service.

“Always remember that when high starting torque is the requirement, series DC motor had been the choice.”

For more details on DC Series Traction Motor visit  

More pages on this topic:

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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:

        THANK U SO MUCH FOR PROVIDING THESE MATERIAL IT IS REALLY USE FUL PLEASE PROVIDE MOCK TEST FOR MECHANICAL ENGINEERING ACTUALLY I DONT KNOW THE PATTERN OF QUESTIONS RRB JE/SE IF U PROVIDE SOME PREVIOUS PAPERS I CAN PREPARE SOME NOTES AND SHRE WITH U BECAUSE AM PREPARING FOR MECHANICAL ENGINEERING COMPETITIVE EXAMS [email protected]

  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.

    • Mahesh Kumar Jain says:

      How does it matter Syed? Will it help you in your preparation? Unless you plan for 70%, chances are bleak.

  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.

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