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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Moving iron instrument

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                  Moving iron instrument
  
• Most common form of ammeters or voltmeters for use in laboratory etc. Are moving iron type. They can be manufactured at cheaper cost and the required accuracy can be obtained.
• There are two types of moving iron instruments.
(1.) Attraction type
(2.) Repulsion type

(1.) Attraction type: It consists of a fixed coil C of insulated copper wound on the bobbin and an iron disc D. The current to be measured ( or a current proportional to the voltage to be measured ) is passed through a coil of wire , the number of ampere turns are required for the operation of the instrument and this number can be made - up by having few turns and large current or vice versa depending upon whether it is a ammeter or voltmeter . In this form of instrument , a small piece of iron is drawn into the core of the coil when the current flows.
Figure. (A)
Whatever be the direction of the current in the coil , the magnetisation of the moving iron in always such that it will get attracted. Thus the instruments are unpolarized instruments i.e they are independent of the direction in which the current passes , hence it can be used on  AC or DC . The principal of moving iron attraction type instruments is represented the figure (A).
                                          In the instrument shown , the gravity control is used which was previously used , but now - a - days spring control is used . The damping method used is air friction damping . In this type , the moving iron , which is made of high Permeability steel ( µ metal ) is essentially pivoted and consists of thin disc . The shape of the disc is such that a suitably divided scale is obtained . The stray field ( field due to neighbouring currents ) usually influence the readings , hence magnetic shielding is required.
(2.) Repulsion type:
• The essential parts of a moving iron , repulsion type instrument are shown figure B; Instrumented copper wire is wound around  a bobbin in the form of a coil . The size of wire and number of turns depends upon the ampere turns required and the magnetic of current to be measured. Inside the space of bobbin which is called as fixed iron and the other is fixed to the spindle which is free to move and called as moving iron.
• when a current pass through a coil , a magnetic field is produced within the hollow space . The two iron pieces are within the field . They are magnetised in the same direction of polarity ,  irrespective of direction of current in the coil . Hence , the two iron pieces will repel each other . Hence , a deflecting torque is produced and moving iron is deflected. 
                               Figure. (B)
• The deflection is indicated by the pointer attached to the spindle . Generally , a spring is used to produce controlling torque . Air friction damping is adopted to produce damping torque in such type of instruments .
*Advantages of Moving Iron Instruments :
(1.) Since there is no current lead to the moving part of the instrument , it quite rhobust and can be operated in vertical / horizontal position.
(2.) The instrument can be used on both a.c. as well as d.c. system . Give reliable service and are capable of giving an accuracy within the limits of both precision and industrial grades.
(3.) Have high operating torque .
(4.) Suitable for low frequency and high power circuits.
(5.) As stationary parts and moving parts are simple , their cost is cheapest.
* Disadvantages:
(1.) The readings shown by the meter get affected due to:
       ( I ) Increase in resistance of coil.
       ( Il ) Decrease in permeability and
       ( III ) Decrease in stiffness of spring ,                                      which are the effects due to increasetemperature .
(2. ) Error is caused due to hysteresis in the iron.
(3. ) The readings are affected due to stray fields.
(4. ) The scale is not uniform because the definition thita is directly proportional to I^2  ( crowded at the beginning ).
(5. ) The instrument readings are true for only one frequency for which it has been designed.
Thank you.
Written by Abhishek Singh E.E

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