LOCO SHED GOMOH

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ACKNOWLEDGEMENT I would like to express my sincere grateful and profound gratitude to LOCO SHED ,GOMOH for providing an opportunity to undergo Vocational Training of 04 weeks in “ELECTRIC LOCO SHED, Gomoh, Jharkhand’’. I bear immense pleasure in expressing my gratitude and thanks to all the Employees of respective shops for their honest teaching, practical demonstration, guidance and suggestion in respective sections. Furthermore, I would like to acknowledge with much appreciation the crucial role of staffs, who gave us the permission to use all required equipment and the necessary materials during our training period. CONTENTS 1. Introduction 2. Locomotives 3. Syntaxs used in Loco 4. Components of Loco 5. Different Sections of Loco 6. Brake Rigging 7. Pantograph 8. Traction Converter 9. Working of Loco 10. Conclusion INTRODUCTION  The ISO-9001-2008 certified Electric Loco Shed, East Central Railway, Gomoh situated in Gomoh. ELECT...
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Permanent Magnet Moving Coil

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Permanent Magnet Moving Coil:-

*Advantages of permanent magnet moving coil instruments:-
(1.) Very small power is required for its operation. Hence,  power consumption is very low.
(2.) Torque to weight ratio of movie system is high.
(3.) Scale is uniform and long scale is obtained.
(4.) It can be used as a ammeter or voltmeter only by using external resistances.
(5.) It is free from hysteresis error.
(6.) Error due to stray magnetic field is negligible.
(7.) Eddy current damping is used to without any extra damping mechanism.
(8.) Strong operating magnetic field due to permanent magnet and iron core arrangement.
* Disadvantages of permanent magnet moving coil instruments:-
(1.) With time the strength of permanent magnets reduces, causing error in reading.
(2.) Thermoelectric e.m.f may cause errors when it is used with shunts.
(3.) Costly.
(4.) Can be used on D.C only and not on A.C. This is because the direction of magnetic field due to permanent magnet is fixed. And if the direction of current in the coil is A.C. then the force produced will be in positive half cycle in one direction and due to negative half cycle in the other direction. Hence the pointer will oscillate and will not deflect.
(5.) Delicate construction, so to be used with due care.
* Construction and principle of permanent magnet moving coil instruments (PMMC INSTRUMENT)
 •Figure (a.) and Figure (b.) Represent simplified skatch, indicating different parts in a moving coil permanent magnet type instrument. A light rectangular coil wound over an aluminium frame is pivoted within the air gaps between the magnetic poles 'N' and 'S' and cylindrical soft iron core.
• The spindle which supports the aluminium frame to provide a Eddy current damping. The controlling torque is produced by two phosphor bronze hair springs coiled in opposite direction, which also servers as leads for current in the coil.
• When current passes through the coil, a deflecting torque is produced due to interaction between permanent magnet flux produced by moving coil.

l, d= length of vertical and horizontal side of coil meters
   N= number of turns in the coil.
    I= current flowing through the coil in amperes.
   Q= final steady- state deflection in radians.
    B= flux density in the air gap wb/m^2 or Tesla. The force produced on each coil side 
= Force × Distance= NBI/d Nm = NBIA Ne meter where, or deflection torque directly proportional to 'I' other factors being constant. As the instrument is spring controlled, Controlling torque directly proportional to thita (Q), where the angle of deflection.
For steady deflection, Tc= Td 
      So,       thita (Q) directly proportional to 'I'
• As thita (Q) is proper to 'l' therefore the scale is uniformly divided.
• If this instrument is connected to measure A.C. quantity, the torque on the moving coil will reverse after every half cycle. The oscillation will be very rapid considering 50 Hz frequency and moving system cannot cope up with such oscillations, hence it remains stationary. So such instrument cannot be used for measuring A.C quantities.
• The moving coil is made of very fine wire, hence its current capacity is very small, therefore when the instrument is used as 
                Shunt resistance multiplier.
ammeter, it is generally used with a 'shunt', when it is used as a voltmeter a high resistance is connected in series with the moving coil which is called as a multiplier.
Thank you.
Written by. Abhishek Singh E.E

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