ADHIPARASAKTHI ENGINEERING COLLEGE

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

INPLANT TRAINING REPORT

Submitted by

M.Saranya

IV-ECE-‘A’

SOUTHERN RAILWAYSPERAMBUR

DEPARTMENTS

o Train Lighting Section

o Delux Section

o Power Section

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Index

S.NO CONTENTS PAGE NO.

1.

TRAIN LIGHTING SECTION 4

AlternatorsRegulators and Rectifiers

BatteryLight and Fan

4678

2.

DELUX SECTION 9

AlternatorCompressor

Condensor And EvaporatorBattery

991112

3.

POWER SECTION 13

SubstationVCB

Relays

131314

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TRAIN lighting section

ALTERNATORS:

Principle of operation:

Alternators generate electricity by the same principle as DC generators, namely, when the magnetic field around a conductor changes, a current is induced in the conductor. Typically, a rotating magnet called the rotor turns within a stationary set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, generating an induced EMF, as the mechanical input causes the rotor to turn.

The rotating magnetic field induces an AC voltage in the stator windings. Often there are three sets of stator windings, physically offset so that the rotating magnetic field produces three phase currents, displaced by one-third of a period with respect to each other.

The rotor magnetic field may be produced by induction (in a "brushless" alternator), by permanent magnets (in very small machines), or by a rotor winding energized with direct current through slip rings and brushes. The rotor magnetic field may even be provided by stationary field winding, with moving poles in the rotor. Automotive alternators invariably use a rotor winding, which allows control of the alternator generated voltage by varying the current in the rotor field winding. Permanent magnet machines avoid the loss due to magnetizing current in the rotor, but are restricted in size, owing to the cost of the magnet material. Since the permanent magnet field is constant, the terminal voltage varies directly with the speed of the generator. Brushless AC generators are usually larger machines than those used in automotive applications.

Construction:

A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature.

Working:

Harmonics in generated voltage waveforms of brushless alternators of inductor type, used in railway coaches are often the cause for excessive heating and tooth tip saturation and compel de-rating of such machines. This paper discusses a novel technique to overcome this problem at the design level itself, by predetermining the generated voltage waveform and analyzing it for the harmonic content for improving the output power quality. Analysis of three-dimensional feature like rotor slot skew is performed with two-dimensional electromagnetic field formulation, which results in significant reduction in computational effort. A modified time stepping finite element method is proposed for shape optimisation of certain design parameters and a multislice technique is employed to take into account the axial variations of the field, introduced by rotor skew. Comparisons of computational and experimental results obtained from a 4.5 kW alternator, confirm the great potential and usefulness of the proposed methodology.

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Frequent breakdowns due to broken shafts in three-phase inductor-type brushless alternators that are used in railway coaches for supplying loads like lights and fans and for charging the coach battery have been reported by the Indian Railways. These failures, besides other mechanical reasons, can be attributed to unbalanced magnetic pull (UMP) due to rotor eccentricity. Accurate calculation of the UMP has always proved difficult due to the inability of machine models to cope with air-gap variations. Hence, analytical closed-form expressions are developed in this paper for the calculation of the UMP and for axial flux, considering various rotor positions. The rotor skew and conical motions of the rotor are also taken into account. A 2-D finite-element method is also proposed for the analysis, for the sake of comparison of results. Furthermore, this paper describes a simple method for detecting even a slight rotor asymmetry on the basis of the generated voltage harmonic pattern, which, on further analysis, illustrates how rotor eccentricity can be identified in the alternator for condition-monitoring techniques.

Fig:alternatorSpecification:

4. 5 KW train lighting system consists of three phase homopolar type alternator and a static Regulator-rectifier unit.

Alternators render a trouble free longing service without practically any maintenance as it is completely free from any moving contacts or winding in

rotor.

The regulator has been designed for a reliable performance in any operational conditions by eliminating transistors and thyristors which are comparatively less reliable.

Brushless alternator is of totally enclosed construction capable of developing a constant voltage of 120 volts at a load current of 37. 5 from a minimum speed for full output to maximum speed. The machines are used forA) charging the coach batteryB) operation of fans & lights etc in Coach.

Output data:

Output voltage-124 v + -5%Voltage setting range-120 v-124 vRated current-37. 5 aMaximum current-43 ampsCut-in-speed 350 RPM (approx 19 kmph train speed with half worn wheel)Minimum speed for full output-550 rpm (approx 29 kmph train speed with half worn wheel)Maximum speed-2500 RPM (approx 140 kmph train speed with half worn wheel)Class of insulation-'f'Resistance between phase-0. 400 ohms at 20 deg c Resistance of field winding-4: 38 ohms at 20 deg c

REGULATOR CUM RECTIFIER:

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Rectifier Regulator units are supplied with the Alternators used for converting the AC to DC for Battery Charging and Train Lighting system.

The rectifier regulating equipment (RRU) along with alternators of 4.5 KW rating so far been used in conventional self generating coaches is based on magnetic amplifier with associated electronic control circuiting. The design of magnetic amplifier based (RRU) is having inherent limitations of voltage regulation.

The rectifier cum regulator unit has mainly following functions:(i) To rectify the 3 phase AC output of the alternator through DC full wave bridge rectifier.

(ii) Regulating the voltage generated by the alternator at the set value.

(iii)Regulating the output current. Clean regulator externally. Open regulator terminal cover and check for signs of overheating in all the terminals/bus bars/etc. Checking:

Check up for loose connections and tighten the same. If the terminal board is found affected due to heat, replace terminal board with new one.

Check for any damage to the phase and field wires /cables inter connecting regulator and alternator and its anchoring arrangement.

Check and secure properly the terminal cover and regulator cover.

If the generator is normal, check the cable termination of the regulator visually for any abnormality.

If the alternator arrived without generation, open the regulator and check for any abnormality and ensure the fuses are intact.

Check the cable for any abnormality from the alternator to the regulator by using test lamp, if found open/short attend the same.

Ensure the residual magnetism is available in the alternator.

If needed change the regulator and ensure the generator by running the alternator with a portable motor.

Fig: Regulator cum Rectifier

Battery:

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Two kinds of batteries are used. They are

Conventional Lead Acid Battery VRLA Batteries

(i)Conventional Lead Acid Batteries:

Record specific gravity of individual cells/mono block. "Switch on" full load of the coach and record individual voltage of cells and total voltage. "Switch off" load. If the specific gravity is less than that painted on the battery box, charge the cells as specified under "Trip Examination" after topping up with DM water, if required.

Use battery charging terminals provided on coaches for charging purposes. Charging should be continued till the specific gravity rises to the value of mentioned in battery box, on "Pilot" cells. In case pilot cells show no appreciable improvement, check specific gravity of adjacent cells. If the specific gravity does not improve in spite of charging, replace the battery by another set and send the defective battery to Depot/Shop for treatment at the earliest. Cells should be handled with due care while unloading and in transit to avoid breakage. Adequate facilities should be created in Depot for treatment of cells which do not pick up charge. Sulphation will be the main cause for this and Sulphated cells should be treated for their recovery as specified.

On completion of charging, record the specific gravity of individual cells. If there is any wide variation in the specific gravity/ voltage of cells, disconnect and replace those cells showing low specific gravity/voltage by spare ones. In case there are more than 1/3 of total cells with low specific gravit y, the entire set should be replaced. Cells showing reverse voltage, zero volts should be withdrawn and replaced by charged cells immediately.

Record individual voltage of cells and the total voltage on full load of the coach.

(ii)VRLA Batteries:

Storage of VRLA Batteries :

The conventional batteries were formed at site and due to this fact a lot of time was required to install the battery. The VRLA batteries are formed in the factory. At site only interconnection of cells is required to be done, hence these batteries are less time consuming as far as commissioning is concerned.

The VRLA batteries are transported and stored in the fully form condition. It is therefore essential that these batteries are installed and commissioned in the shortest possible time after their dispatch from the factory. This is because all the batteries including VRLA batteries lose their charge due to self discharge. If these batteries are allowed to remain idle for a very long time, say more than six months these battery may get damaged beyond recovery due to sulphation.

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LIGHT AND FAN:

FAN:

The fan body, guards and blade shall be thoroughly cleaned with cloth. All fans shall be opened and condition of commutator, brushes and brush gear shall be thoroughly checked. Action should be taken where necessary as given under"Trip Attention".

Studs used for fixing the fan to coach body, shall be checked and tightened, wherever necessary. Availability of all the three fixing studs should be ensured. All the switches controlling the fans shall be checked for its smooth operation and correctworking and replaced, where necessary. Fan regulators in Upper class coaches shall be checked for smooth operation from one position to the other. In case the regulators are not regulating the fan speed, the resistance box shall be checked and replaced, where necessary. Fan blades shall be replaced if found bent, or if there is no proper air discharge.

LIGHT:

Open each fitting with the dome key and remove the dust of the fitting both from inside and outside. Ensure free operation of locking mechanism and replace defective fitting. Clean glass domes first with wet cloth and then with a clean dry cloth. Replace rusted fittings and fittings with damaged surface. n Check up wattage of lamps and replace with that of correct wattage. n Check up whether toggle switches are marked to indicate lighting control "L", night light control `NL', side lamps in guards compartment as `SL', tail lamps as `TL-Rear', `TL-Front', luggage room as `LRL'. Check up all lighting circuit fuses in each coach for correct sizes and replace if necessary. Stencil the size of fuses near the locations, if not already done.

fig:light

DELUX SECTION

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Air conditioning:Air conditioning of railway coaches on Indian Railways began in 1960s. These were equipped

with under slung equipment's, interconnected with pipelines. The introduction of self contained roof mounted package units in coaches, with complete equipment's, pre-charged and tested needing only electrical and ducting connections is of recent origin. With the introduction of more and more fast trains on Indian Railways, the need for air-conditioned coaches has also increased. Not only for improving comfort, but also from operating point of view, since with higher train speeds, the need to avoid opening of windows due to wind resistance considerations also assumes importance.

ALTERNATORS:

DEVELOPMENT OF 25 KW ALTERNATORS FOR SELF-GENERATING AIR-CONDITIONED COACHES.

Belt driven alternator along with rectifier-regulator is used to generate electrical power by utilizing the mechanical power of the train to provide power supply for air conditioning system, light and fan loads in the coaches. At present, there are mainly two types of coaches (i) Air-conditioned coaches which are provided with 18/22.75 kW alternators with rectifier-regulator and (ii) Non-AC coaches with 110 V system which are provided with 4.5 kW, 110V ac alternator. In order to improve the reliability of these alternators for AC coaches, it is necessary to provide adequate design margins in the rating. Research, Designs and, Standards, Organization (RDSO) has undertaken development of 25 kW alternator and regulator using state-of-art technology of power electronics and controls. RDSO has successfully developed these alternators indigenously through the existing manufacturers. These alternators are now in regular use by the production units. The design features of various makes have also been standardized to ensure inter-changeability.

COMPRESSOR:

The compressor normally consists of the following elements. a. The compressing element, consisting of air cylinders, heads and pistons, and air inlet and discharge valves. b. A  system  of  connecting  rods,  piston  rods,  crossheads,  and  a  crankshaft  and flywheel  for transmitting  the  power  developed  by  the  driving  unit  to  the  air cylinder pistonc. A  self-contained  lubricating  system  for  bearings,  gears,  and  cylinder  walls. Compressor includes a reservoir or sump for the lubricating oil, and a pump, or other means of delivering oil to the various parts.   On some compressors a separate force-fed lubricator is installed to supply oil to the compressor cylinders. d. A regulation or control system designed to maintain the pressure in the discharge line and air receiver (storage tank) within a predetermined range of pressure. e. An unloading system, which operates in conjunction with the regulator, to reduce or eliminate the load put on the prime mover when starting the unit.

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Location of CompressorThe location of air compressors and the quality of air drawn by the compressors will have a

significant influence on the amount of energy consumed. Compressor performance as a breathingmachine improves with cool, clean, dry air at intake.

Air Intake TemperatureThe effect of intake air on compressor performance should not be underestimated. Intake air that

is contaminated or hot can impair compresso r performance and result in excess energy andmaintenance costs. If moisture, dust, or other contaminants are present in the intake air, suchcontaminants can build up on the internal components of the compressor, such as valves,impellers, rotors, and vanes. Such build-up can cause premature wear and reduce compressorcapacity.

The compressor generates heat due to its continuous operation. This heat gets dissipated tocompressor room/ chamber leading to hot air intake. This results in lower volumetric efficiencyand higher power consumption. As a general rule, “Every 4oC rise in inlet air temperatureresults in a higher energy consumption by 1percent to achieve equivalent output”. Hence theintake of cool air improves the energy efficiency of a compressor

When an intake air filter is located at the compressor, the ambient temperature should be kept ata minimum, to prevent reduction in mass flow. This can be accomplished by locating the inletpipe outside the room or building. When the intake air filter is located outside the building, andparticularly on a roof, ambient considerations may be taken into account.

Inter and After-CoolersMost multi-stage compressors use intercoolers, which are heat exchangers that remove the heat

of compression between the stages of compression. Intercooling affects the overall efficiency ofthe machine.

As mechanical energy is applied to a gas for compression, the temperature of the gas increases.After-coolers are installed after the final stage of compression to reduce the air temperature. Asthe air temperature is reduced, water vapor in the air is condensed, separated, collected, anddrained from the system. Most of the condensate from a compressor with intercooling is

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removed in the intercooler(s), and the remainder in the after-cooler. Almost all industrialsystems, except those that supply process air to heat-indifferent operations, require after-cooling.

In some systems, after-coolers are an integral part of the compressor package, while in othersystems the after-cooler is a separate piece of equipment. Some systems have both.

Use of water at lower temperature reduces specific power consumption. However, very lowcooling water temperature could result in condensation of moisture in the air, which if notremoved would lead to cylinder damage.

Pressure SettingFor the same capacity, a compressor consumes more power at higher pressures. Compressors

should not be operated above their optimum operating pressures as this not only wastes energy,but also leads to excessive wear, leading to further energy wastage. The volumetric efficienc y ofa compressor is also less at higher delivery pressures

CONDENSER &EVAPOURATOR:

To turn the basic vapour compression cycle into a practical refrigerator, the evaporator should superheat the refrigerant after all the liquid has evaporated. It is not practical to control precisely at the point where evaporation is just finished. Unless it is complete, some liquid will leave the evaporator, which is useful cooling potential wasted. Moreover, compressors do not generally appreciate liquid arriving with the vapour. It can cause damage. So control is provided in such a way as to ensure that the vapour leaving the evaporator is superheated.

The upper diagram shows the refrigeration circuit, and the lower one is the corresponding P-h diagram The process starts with evaporation of the refrigerant in the evaporator. Point 2 is in in the vapour region, to the right of the saturated vapour curve. Compression raises the pressure of the

refrigerant, point 3. The vapour is now hot, and is cooled before condensation starts.

It is not possible in practice to control exactly the completion of condensation. We want liquid to flow through the line from the condenser to the control or expansion valve. If some vapour is present here, it can cause excessive pressure drop and reduction in performance of the system. The pressure drop should occur in the valve itself. Some degree of subcooling is necessary to ensure 100% liquid flow. This subcooling can occur in the condenser, and further cooling of the liquid can take place between the condenser and the valve. Point 4 is now in the liquid region, to the left of the saturated liquid curve, the pressure is reduced in an expansion device, and the refrigerant is returned to its original condition 1.

Superheat and Subcooling occupy quite small sections of the diagram, but they are very important for the effective working of the system. When refrigerant flows from one process to the next it always moves through the pipes as either a superheated vapour or a subcooled liquid. The amount of superheat or subcool may be quite small.

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Connect up, use fans to circulate air over the evaporator (the air will be cooled), and condenser (the air will be heated), switch on the compressor and we have a refrigeration machine. Sounds simple, but careful design and specification of components is needed. The control valve is a key component. Usually termed "Expansion Valve" this device regulates the superheat at the outlet of the evaporator. The temperature sensor at the outlet of the evaporator is connected to the valve to provide feedback on the adjustment of the valve. Most valves work automatically by means of a

diaphram, and are termed Thermostatic Valves, whilst other types are electronic.

The properties of the Refrigerant or Working Fluid are known to a high level of accuracy and by measuring the pressure and temperature at points 1, 2, 3, 4 the P-h diagram can be established. In practice only two pressure measurements 2 and 3 are required. Instrumentation and computer techniques are now available which allow fast diagnostics of almost any system.

BATTERY

(Similar to lighting section)

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POWER SECTION

SUBSTATION:

Current rail gaps are also provided where the substations feed the line (diagram, left). Normally, each track is fed in each direction towards the next substation. This allows for some over supply and provides for continuity if one substation fails. These substation gaps are usually marked by a sign or a light which indicates if the current is on in the section ahead. A train must stop before entering the dead section. Since the current may have been switched off to stop an arc or because of a short circuit, it is important that the train does not connect the dead section to the live section by passing over the gap and allowing its busline to bridge the gap. Some of the more sophisticated systems in use today now link the traction current status to the signalling so that a train will not be allowed to proceed onto a dead section.At various points along the line, there will be places where trains can be temporarily isolated electrically from the supply system. At such places, like terminal stations, "section switches" are provided. When opened, they prevent part of the line for being fed by the substation. They are used when it is necessary to isolate a train with an electrical fault in its current collection system.

VCB:Circuit breakers provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. Circuit breakers are mechanical switching devices capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions. Circuit breakers are useful for controlling and protecting electrical systems, apparatus and networks. Electrical power distribution systems and their components need protection from numerous types of malfunctions, including overcurrent conditions, overvoltage conditions, undervoltage conditions, reverse current flow, and unbalanced phase voltages. Electrical distribution and protection equipment is an important element in many applications, particularly those employing medium to high electrical voltages. The integrity of operability of any power distribution system ultimately depends on the proper functioning of the circuit breakers.  Circuit breakers are rated by voltage, insulation level, current interrupting capabilities, transient recovery voltage, interruption time, and trip delay. The circuit breaker is divided into an AC circuit

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breaker and a DC circuit breaker according to an applied line. Typically, circuit breakers include at least one circuit interrupter, which contains a spring-powered operating mechanism that opens electrical contacts in response to abnormal conditions in order to interrupt the current passing through the conductors in an electrical system. The medium in which circuit interruption is performed may be designated by a suitable prefix, for example, air-blast circuit breaker, gas circuit breaker, oil circuit breaker, or vacuum circuit breaker. The vacuum circuit breaker is one of the breakers by which the circuit can be broken rapidly by extinguishing an arc in a vacuum chamber when the circuit is opened/closed and when the circuit is broken by a generation of the accident current. Vacuum circuit breakers in particular are useful for controlling and protecting electrical systems.

Circuit breakers provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. Circuit breakers are mechanical switching devices capable of making, carrying, and breaking currents under normal circuit conditions and also making, carrying for a specified time, and breaking currents under specified abnormal conditions. Circuit breakers are useful for controlling and protecting electrical systems, apparatus and networks. Electrical power distribution systems and their components need protection from numerous types of malfunctions, including overcurrent conditions, overvoltage conditions, undervoltage conditions, reverse current flow, and unbalanced phase voltages. Electrical distribution and protection equipment is an important element in many applications, particularly those employing medium to high electrical voltages. The integrity of operability of any power distribution system ultimately depends on the proper functioning of the circuit breakers.  Circuit breakers are rated by voltage, insulation level, current interrupting capabilities, transient recovery voltage, interruption time, and trip delay. The circuit breaker is divided into an AC circuit breaker and a DC circuit breaker according to an applied line. Typically, circuit breakers include at least one circuit interrupter, which contains a spring-powered operating mechanism that opens electrical contacts in response to abnormal conditions in order to interrupt the current passing through the conductors in an electrical system. The medium in which circuit interruption is performed may be designated by a suitable prefix, for example, air-blast circuit breaker, gas circuit breaker, oil circuit breaker, or vacuum circuit breaker. The vacuum circuit breaker is one of the breakers by which the circuit can be broken rapidly by extinguishing an arc in a vacuum chamber when the circuit is opened/closed and when the circuit is broken by a generation of the accident current. Vacuum circuit breakers in particular are useful for controlling and protecting electrical systems.

RELAYS

GROUND RELAY:

An electrical relay provided in diesel and electric traction systems to protect theequipment against damage from earths and so-called "grounds". The result of such arelay operating is usually a shut-down of the electrical drive. Also sometimes called anEarth Fault Relay

NO-VOLT RELAY

A power circuit relay which detected if power was lost for any reason and made sure that the control sequence was returned to the starting point before power could be re-applied. See Motor Protection.

OVERLOAD RELAY

A power circuit relay which detected excessive current in the circuit and switched off the

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power to avoid damage to the motors.

CONCLUSION:

Thus the SOUTHERN RAILWAYS has performed lots and lots of services in transport. This report has highlighted with brief explanations about some of the important sections of the train.

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