INDEX

Sr No. Topic Page no.1 Comparative features of AC locos 2

2 Pantograph 3

3 Main transformer 6

4 Tap changer 9

5 Rectifier 12

6 Static converter unit 13

7 Arno converter 15

8 Traction motor 17

9 DJ (circuit breaker) 20

10 Locomotive bogies 22

11 Brake system 24

12 Protective relays 27

13 Changes needed in traction 30

14 Three phase loco 31

15 Energy conservation in loco 34

1. Comparative features of A.C. locos

WAG5 WAG7 WAG9 WAP4 WAP5Horsepower 3850 5000 6000 5000 6000

Max. service speed 80 100 100 140 160

Type of TM HS15250

HS15250

FRA6068

HS15250

6FXA7059

Max. tractive effort at starting

33.5 t 42 t 47 t 30.8 t 30 t

Cont. tractive effort 20.6 t 24 t 33 t 24 t 26 t

Total weight of loco 126 t 123 t 123 t 112.8t 78 t

Break system AIR/RHEO

AIR/RHEO

AIR/REGN

AIR AIR/REGN

Transformer in KVA 3900 5400 6531 5400 7475

Wheel arrangement CO-CO CO-CO CO-CO CO-CO BO-BO

Traction motor o/p

voltage 750 750 2180 750 2180current 840 900 540 900 370

power 585 630 1150 630 850No. of axles 6 6 6 6 4

Adhesion 29 ℅ 35.70℅ 38 ℅ 35 ℅ 38 ℅

Type of bogies CAST FABRI FABRI FABRI FABRI

Gear ratio 18:64 18:64 DIRECT 23:58 DIRECT

2. PANTOGRAPH Pantograph is a current collecting device which is mounted on both ends of locomotive roof on insulator and collect the current from OHE and supply it to power system of locomotive at various speed and different climate/wind condition smoothly.

OPERATING PRINCIPLE

Basically compressed air raises and spring lowers the pantograph. The sole function of compressed air is to cancel the lowering effort of the spring and it has no direct effect on the pantograph. When the pantograph is raised and the pressure is maintained in servomotor, the piston is kept still and the articulation system is entirely kept panto free raised only by the raising spring. Rising spring controls the oscillation of pantograph. Should lack of air occur, the pantograph collapse by itself gradually by lowering spring against the raising spring. The whole pantograph is alive, its own parts are used as conductor, and the current collection is made on the frame with the flexible shunts at moving parts.

RAISING OF PANTOGRAPH

When we put ZPT on ‘1’, the VEPT of rear panto gets energized by battery supply and opens the compressed air path to panto servomotor through throttle valve. The compressed air are rushes to panto servomotor gradually and presses the piston against the tension of lowering spring which moves the eyelet rod backward, thus permitting rotation of horizontal spindle under the tension of raising spring. As the horizontal spindle rotates the pantograph raised through articulation assembly till it touches contact wire. After the completion of piston stroke the air servomotor plays no further part.

LOWERING OF PANTOGRAPH

When we put ZPT on ‘0’, the VEPT of concerned panto gets de-energized and stop the air supply to panto servomotor and also exhausted the remaining pressure of servomotor gradually through VEPT valve As the pressure of servomotor gets exhausted piston return under the action of lowering spring due to which eyelet rod moves forward

and rotates the horizontal spindle in such a way that the pantograph get lowered through articulation system. THROTTLE VALVE:

A throttle valve is provided in air path of panto servomotor. It controls the rate of admission and escapes of air flow in such a way that raising and lowering can be done with out shock either on contact wire or on the base.

VEPT valve:

It is electro pneumatic valve operated by 110 volt control supply and controlled by ZPT key. When ZPT key is kept on ‘1’ rear cab VEPT gets energized and opens the path of air to panto servomotor and when ZPT key if kept on ‘0’ VEPT gets de-energized and stop the air supply towards panto servomotor. On its body there is a knob for manual operation of VEPT in case of malfunctioning of VEPT.

ZPT: For raising and lowering the panto the ZPT key is provided on both the control staid, which having following positions.

0 - Both VEPT de-energize - both panto down.1 - Rear VEPT energize - rear pento raised.2 - Front VEPT energize - front panto raised.½ - Both VEPT energize – both panto raised.

DATA Operating pressure 6.6 to 8.0 kg/cm² Panto start lowering between 3.0 and 3.5 kg/cm² The articulation system is designed to allow an extension of 2.46

meters Raising time (1.5 meter) is 6 to 10 second Lowering time (1.5 meter) is 6 to 10 second

3.LOCO TRANFORMER

This is a main transformer of locomotive. The 25 KV single phase AC power supply of OHE is fed to the winding of regulating transformer through main bushing. The winding is equally divided into 32 taps. These taps are connected to tap changer.

The complete winding of transformer is oil immersed in a tank and oil is cooled through oil cooling system containing MPH and MVRH. Above the transformer there is oil conservator, the pipe leading to it serving as safety valve. Above this safety valve there is an oil overflow chamber with a discharge pipe leading the blown out oil underneath the loco body. The air does not come in to contact with the oil in the conservator direct by having been completely dried before by means of silica gel air gryer. The transformer is fitted with oil level indicator on both the sides. There is a red mark at 15 c. normally the oil should not go below the red mark.

The transformer has three lag. Lag one carries the winding of the regulating transformer stepping down the voltage of the overhead system to a value permissible for the equipment.

The series winding A-32 ---- A-33 has turns and a cross sectional area of 27.45 mm² The main winding A-0 ----- A-32 has 960 turns and a cross sectional area of 27.45 mm² Therefore, the total no. of turns in a complete winding of the regulating transformer will be N1= 80 + 960 = 1040 turns

According to the actual position of the tap changer i.e.

Pos 0, 1, 2, 3…28, 29,30,31,32

The active no. of turns varies from

NR = 0, 30, 60, 90, 120 ….840, 870,900,930,960 turns

In addition to the winding of the regulating transformer Leg 1 carries the electrically separated winding a-0 ---- a-1 of the auxiliary circuits also. This winding has 18 turns and cross sectional area of 248 mm².

The leg 2 and 3 carries the primary and secondary windings of the main transformer. The indication effect of the winding of leg 3 on the winding of leg 2 varies according to the position of the tap changer. The design of the two legs is similar, the difference being in the cross sectional area only. The primary windings both legs are connected in series and each leg has Np = 288 turns. The beginning of the primary windings led to the terminal A 34 and is connected through the tap changer with the tapping A-0 to A-32 of the regulating transformer. The end of the following is permanently connected to A-0 internally.

BRIF DATA OF POWER TRANSFORMER

Type HETT 3900Supplier NGEF, CROMPTON GEAVES, BHELPhase Single Cooling OFAFNo of taps 32Voltage Primary Maximum 27.5 KV

Nominal 25.0 KVMinimum 22.5 KV

Secondary Maximum 1058V in each windingminimum 869 in each winding

Primary input 4170 KVASecondary output 3900 KVAAux. system output

270 KVA

System Single phase, 50 c/s oil immersed, air cooled with forced oil circulation primary single winding and secondary with double winding with equal ratings.

Rated secondary current of each winding

2250 amps.

4. TAP CHANGER (GRADUATOR)

The tap changer is directly built on to the transformer. The tapings of the transformers are bought out and arranged in circular fashion on an insulated contact plate. There are to rows of contact segments which are aligned on outer and inner circles of the contact plate. An arm which is known as selector arm is driven by shaft at the center of the contact plate. Two rollers are situated at the edge of the selector arm. These rings are provided in front of the contact plate. The center shaft which extends outside the tap changer casing is driven by an air servomotor known as SMGR. The design of the air servo motor is such that once the selector arm begins its movement, it can be stopped only at the required tap (not in between two taps). The connection between the inner or outer ring to the transformer is being established by means of CGR contactor.

METHOD OF OPERATION

The selector arm is actuated by the driving shaft through an intermittent gearing comprising of drive wheel, Lantern gear pinion and stopping wheel. This driving shaft also operates the CGR cam shaft in sequence with the operation of contact rollers. The opening and closing sequence of CGR contactors are given below:

CGR I CGR II CGR IIIEven notches open closed closedIn bet. notches closed closed openOdd notches closed open open

Before moving contact roller leaves the zero tap contact segment, it touches the first tap segment. During this the CGR1 contactor closes inserting the diverter resistance RGR in between tap ‘0’and tap ‘1’ through RGR. This resistance RGR restricts the short circuit current when the selector arm further moves fully on tap 1, the inner contact roller breaks the contact with zero tap. Meanwhile CGR II contactor opens and cuts off RGR from circuit, Like wise when the selector arm moves from first tap to second tap. The contact roller will continue to make connection between inner segment and inner ring. This is due to over lapping contact segment. At the same time CGR I, CGR II are closed again setting the resistor RGR in between the short circuited winding. Now the service current flows from the contact ring in the selector through the resistor RGR. When the selector arm further moves, the outer roller leaves the tap 1 segment and breaks the contact. At the same time CGR gets opened and CGRII and CGR III are closed. This again cuts off the resistor RGR. The opening and closing of CGR contacts is carried out by cam shaft which is driven by the main shaft through gear arrangements. This ensures a perfect relationship between the movement of selector arm and the operation of CGR contactors. A high resistor RGR serves as the connection between equal potential, which ensures that branches of the circuit being interrupted at the given potential.

CONTROL OF TAP CHANGER BY MP

The servo motor which drives the graduator is controlled by electro valves VE1 and VE2 for progression and regression respectively. These electro valves are remote controlled from driver desk by the master controller MP. The master controller hand wheel MP has 4 position 0, --, + and N. When MP is placed on ‘+’ VE! Will be energized and progression will take place. When MP is placed on ‘0’ VE2 will be energized and regression will take place. ‘—‘position is used for notch by notch regression and N shows the neutral position. Position ‘—‘and ‘+’ are unstable position, if the hand wheel is released in such position it is returned to N by spring force. If P is placed on 0 the tap changer regresses to ‘0’ notch at a time.

5. RECTIFIRE

In electric loco mainly two silicon rectifier blocks RSI 1 and RSI 2 are provided for converting AC to DC. They are bridge connected. Continuous current retting of each block is 1000 amps.

Each rectifier blocks are provided with set of tells tale fuses. Each rectifier bridge consists of four arms and each arm carries four fuses. In case of puncturing of silicon diode in a particular block, the main fuse melts and the corresponding tell tale fuse also melts which causes the micro switch to operate. By closing of micro switch, the related relay will be energized which make glows respected pilot lamp in cab 1 and cab 2 the defective block or arm can be curtained by visual inspection of rectifier cabinet . The melted tell tale fuse can be identified by the black button projecting out. The maintenance of the rectifier is limited to an inspection every three months to check whether the cell is screwed tightly in to position. Any dirt which may have accumulated in the rectifier must be removed by using a rag and brush. It should be specially observed that the protecting cover of each cell is always clean. If a protecting cover becomes brittle or is no longer tightly fitted to the cell casing, this cap must e replaced. 6. STATIC CONVERTER UNIT FOR AC-DC UNIT

Replacement of Arno converter by solid state converter unit has always been a cherished dream of rolling stock engineers for utilizing the 415 V +/- 5% balanced supply for feeding the auxiliary motors of locomotive. Failure of auxiliary motors, especially the compressor motor has been causing concern to the maintenance engineers apart from failure of the Arno converter itself. SE rly had first opportunity in the year 1988 to make use of static inverters on 6 nos WAG6A locomotives imported from M/s ASEA, Sweden. Thereafter, it was the turn of western and central railways to maintain and operate 180 KVA SI units on WCAM2 and WCAM3 /WCAG1 locomotives respectively. Currently, electric loco shed, kalian boasts of highest holding of electric locos equipped with “state of art” static inverter unit manufactured by M/s. GEC Alsthom, rich experience has been gained by kalian loco shed in maintaining these static inverter.

COMPONENTS OF SI UNIT

On WCM3 locos, SI unit made by ACEC Belgium has been provided. This set converts 1500 V DC supply to 415 v AC for supply to all auxiliary machines. RFPR, CHBA, cab heaters and 230 V AC for TFS 1 & 2. This set consists of chopper and inverter unit with electronic and computerized circuits provided in cubicles and mounted in side the locomotive. It is cooled

by three blowers MVCON 1-2-3. This is located behind cab no. 2 drivers seat in corridor.

The whole unit consists of: RS 1-3, QRS 1-3 under AC catenary(25 KV AC) Feeding and control block with current sensor. Input fuses CCIN, contactors CIN, CCUL. Input inductance DC link

resistance chopper inverter. Three phase contactor for cooler blower motors. Indication panel

FUNCTION OF SI UNIT:

SI unit gets activated when CCBA fuse is intact. HBA is in No. 1 position. 110 V DC supply is available for feeding the control block. It will be indicated on SI unit by illuminating “control OK” green indication. When the HV supply is available by closing DJ in AC section or DS section , in put contactor CIN closes, ‘ in put voltage ok” green indication will illuminates with CCIN fuse intact and SI unit starts functioning. No sooner DJ is closed SI unit makes the 415 V AC 3 phase supply available and “output voltage ok” green indicator will illuminate. At the same time MVCON 1-2-3 starts automatically for cooling down the SI unit.

7. ARNO CONVERTER

Arno converter is a device which convert single phase AC in to three phase AC. The three phase supply needed for the three phase induction motors which used in blowers, exhausters an oil pumps. To supply three phase power to three phase induction motors arno converter is used. Arno converter is rotating device technical data of arno converter provided by

M/s. Jyoti Ltd. Baroda Is given below.

Single phase input Three phase out putKVA 150 KVA 120Volts 380 Volts 380Amps 395 Amps 190Frame VA- 330 Frame VA- 330Class ‘B’ Class ‘B’

Connection StarRPM 420Cycle 50

Due to the voltage variation the speed of the arno is also varies so the out put three phase supply is not constant but varies with the OHE voltage which is not desired. Due to this reason now a days arno converter are replaced by solid state static converter unit which is known as SI unit.

8. TRACTION MOTORS (DC series motor)

The traction motor is a dc series motor four pole or six pole forced ventilated machine arranged for axle mounting on sleeve baring and supported on the opposite by the resilient suspension unit, transverse movement is limited by the flanges of axle. These motors are axle hung, nose suspended type and are provided with grease lubricated roller bearings for armature as well as for suspension. Special provision has been made in design of the motors to ensure the locomotive operates satisfactorily on flooded track, to max. Flood level of 20 cm , above rail level.

The main parts of motors are given below1. Magnet frame armature and shields.2. Brush holders and brushes.3. Commutator4. Armature5. Stator6. Armature windings7. Field windings8. Inter poles9. Armature bearings10.Axle bearing

Technical data

Type HS 15250 AContinuous out put 630 KWVolts 750 VCurrent 900 Amp.Speed 895 RPMNumber 6 Per LocoField Series field with commutating polesInsulation Class HNo. of poles Main 6, commutating 6Ventilation 90 cu meter/min

Generally in locos there are six traction motors. Three motors per bogies and each motor driving one axle directly through gears. The motors M1 to M6nare supplied jointly by the two silicon rectifiers connected in parallel through contactors L1 an L2. Each rectifier units RSI is connected to separate secondary winding TFP 1, 2 and the smoothing the current thus rectified in carried out by means of two smoothing reactors SL1 and SL2.

CHANGING THE DIRECTION BY REVERSER

The traction motor double reverser J1 and J2 which are pneumatically controlled connected the field coils of the motors in such a way that these carry current in one direction or in the other, thus enabling the locomotive to run in both direction or in the other , thus enabling the locomotive to run in both directions . The shaft of the reverser is connected with the servo motors each controlled by 2 electro valves, each valve corresponding to a direction of running . these electro valves are remote controlled from the driver desk by operating the reverser handle ‘ MPJ ‘ which has three position

Position ‘F’ – loco moves forward. Position ‘0’ – handle can be extracted electro valves de energized and

reverser remains in the occupied position. Position ‘R’ – Loco moves in reverse direction.

INCREASING OF TENSION TO THE TRACTION MOTORS

By increasing the notch of the tap changer using SMGR the we can increasing the speed of the traction motor after applying maximum tension to the traction motor if the required speed can not be attended , the field coils of the traction motors can be shunting is done dead resistance are introduced in parallel to the field coils. Shunting is effected in 3 steps by four electro pneumatic contactors for each motor or pair of motor. These contactors are remote controlled by the shunting controller MPS which has 5 positions. Shunting can only be done if 20 or more notches are taken, as the cam contact of GR on the control circuit of shunting contractors will close only on notches 20 – 30. Shunting should only be done when it is absolutely necessary and only a after having applied the max. Permissible tension to the traction motors. It should be ensured that the max. Permissible limit of intensity is however not exceeded.

ISOLATING TRACTION MOTORS For isolating traction motors a ‘motor cut out switch’ HMCS is provided which has got the 4 position.

9. DJ (CIRCUIT BRAKER)

The high voltage circuit breaker DJ is special type of electro pneumatic contactor mounted on the roof of the loco. The electrical equipment of the loco is connected to or disconnected from the OHE by means of the circuit breaker. it is designed to open the circuit rapidly about 0.03 compressed air apart from operating the breaker acts as a means of extinguishing the are also.

PRINCIPLE OF WORKING

The opening and closing of the DJ is effected by a servo motor which is supplied with compressed air from the reservoir TDJ minimum pressure 6.5 KG. if the air pressure is less than 6.5 KG it is possible to close DJ but it can not be open if the pressure is very less and the loco may risk an over current. To close DJ it is necessary to admit compressed air on the right side of the piston. This is affected by a closing device, which is operated by the electro valve EFDJ, when EFDJ is energized, the passage opens air is admitted on the right side of the piston and the DJ closes. The air pressure

which was admitted close the DJ is automatically exhausted after the DJ closed. At the same time it should be ensured that air pressure does not enter the left side of the piston, otherwise this air pressure will cause the DJ to open and cause a second detonation. To prevent the air pressure from entering the left side the piston, the electro valve MTDJ which controls the opening device must be energized. When MTDJ is energized the opening device passage is closed and air pressure can not enter the left of the piston. The DJ is locked in the closed or open position by a mechanical locking device and prevents it from leaving the position due to vibration etc. For closing DJ, energized EFDJ and MTDJ together. After DJ has closed EFDJ is to be de-energized, and for opening DJ, de-energized MTDJ can be done either of voluntarily by the driver or by the action of the safety relays. DJ can be controlled from the driver cab simply by using the BLDJ switch on the switch panel. The pilot lamp LSDJ gives the indication that DJ is currently open or close. If the lamp is glow it shows the DJ is open.

VCUUM CIRCUIT BREAKER

Mostly the air blast type circuit breaker is used as a DJ is electric traction but now a days OCB are replaced by the vacuum circuit breaker due to the following advantages

1. Less maintenance2. Space saving3. Greater reliability4. Simplified control5. Quite in operation

10. LOCOMOTIVE BOGIES

Bogies in locomotive are provided to permits long length of locomotive body to negotiate the curves. A small length of bogies is desirable. The length of bogies is decided wheel base. Bogie wheel base shall be well proportioned to permit the bogie negotiating the curve and also prevent tipping and jerking. The locomotive has two or more bogies on which the body is mounted. The distance between the centers of extreme wheel known as the total wheel base.

BOGIES CLASSIFICATION

Bogies are classified based on

No of axles Type of axle drive

The type of axle drive and no. of axle in bogies is also called the wheel arrangement. Wheel arrangements are classified as B, BO, CO

B - Two axles & axles mechanically coupledBO - Two axles & axles are independently drivenCO - Three axles & axles are independently driven

Locomotive always have two or more bogies. So the wheel arrangement of the locomotive is designed as B-B, BO-BO, CO-CO.

WEEL ARRENGEMENT OF LOCOMOTIVE

Different type of wheel arrangement is available on existing fleet of Indian railways locomotives as under:

Wheel arrangement Locomotive typeB-B WAG1, WAG2, WAG3,WAG4,YAM1

BO-BO WAM1,WAM2,WAM3,WAP5 ALL EMUSCO-CO WAM4,WAG5,WAG6C,WAP4,WAG9,WAP7

BO-BO-BO WAG6A,WAG6B

BOGIES COMPONENT

A bogie of a locomotive is an assembly of following components.

1. Bogie frame2. Wheels3. Axles4. Springs5. Axles boxes6. Supports for traction motors7. Support for brake rigging brake cylinder8. Friction dampers/snubbers.

SUSPENSION

Suspensions in bogies are provided to reduce the vibrations. The vibrations are picked up by the wheel which is mounted on railway track which it self if shaking up the down due to irregularities in the surface. The

suspension system also balances the vertical loads between the wheels and provides passenger comfort by reducing vibration in the vehicle body. The suspension between the axle and the bogies frame constitute the primary suspension. The suspension between the bogies fram and the vehicle body is called secondary suspension.

Mainly three type of bogies are used is given below.

1. Trimount bogie2. Flexi coil bogie3. High adhesion bogie

11. BRAKE SYSTEM OF LOCO

A. Pneumatic circuit of loco MR air system BP charging system Vacuum charging system of different loco Loco brake system of different loco

B. Pneumatic valvesFunction, location, use of different pneumatic valves/equipment like;A-9, SA-9, DAB, MU-2B, DV, VEF, AIV, HB-5, H-5, H-4, VA-1R, VA-1B, AEV, AIR ADMISSION VALVE, VAC. RELIEF VALVE, SYN. VALVE, F-1,6/8 kg FEED VALVE, RGCP, SWC, A-8,MTP COC etc.

IRAVB.2 BRAKE SYSTEM

IRABB.2 dual brake system had been designed by Indian railways for application in main line WAG5/WAG7/WAP1 AC locos for hauling both graduated release automatic air braked train as well as standard vacuum braked train. The system comprises WABCO brake elements, already provided in 28-LAV-1 brake system used in WDM-2 class diesel-electric locos in Indian railways.

The system is a composite one and distinctly comprises the following elementary brake system.

1. Independent loco brake system with MU operation.2. Twine pipe graduated automatic brakes for hauling air braked train.3. Standard vacuum brake controls for hauling vacuum braked train.

Besides, the IRAVB.2 brake system also supplies compressed air for operation of the following auxiliaries.

1. Load2. Pantograph3. Electro pneumatic sanding4. Pneumatic horn5. Pneumatic wipers.

The complete IRAVB 2 dual brake system is compressed air controlled and essentially comprises 3 no. MCP of 000 liters, or its varies with the type of loco. FAD for supply of compresses air 8-10 kg/cm² 2 nos. of MPV of 250 liters. FAD for evacuating vacuum train pipe at 20-20” HG, and relevant elementary valves for achieving the system and features.

Depending upon the air braked train length either 2 or 3 MCP are kept ‘ON’ for vacuum braked train one compressor and one MPV are kept ‘ON’.

MAIN AIR SYSTEM

Compressor/compressors delivers compressed air at 8-10 kg/cm² to system via respective check valve (NRV) to flow past. After cooler

centrifugal dirt collector, MR-1, MR-2, NRV, MR-3, MR-4 and then to air brake system.

BRAKE SYSTEM 1. Independent loco brake system2. Syn. Loco brake system3. BP charging system4. Vacuum brake system.

INDEPENDENT LOCO BRAKE SYSTEM

The system by which the brakes on loco are applied or released independently is called as straight air brake system. The main parts of the system are as follows.

1. SA-9 valves2. MU-2B valve3. C-2 relay valve4. Duplex check valve5. Bogies COC with vent.6. Brake cylinders.

IMERGENCY APPLICATION OF BRAKE

When the A-9 brake valve handle is moved to emergency position, the BP pressure drop to zero at a much faster rate than that at normal service application, and as such ensures a faster emergency brake application. The BP can be drop to ‘0’ by putting A-9 to emergency even through the COC of A-9 are closed.

12.PROTECTIVE RELAYS USED IN AC LOCO

1. High voltage overload relay QLM The relay QLM is fed by means of the high voltage current transformer TFILM (250/5A).This causes the high voltage circuit breaker DJ to trip out, if the current taken in by the main transformer exceed the setting value of the relay 300A.

2. Overload relays for silicon rectifiers (QRSI 1 and QRSI 2) The relays QRSI 1-2 are fed by means of the rectifier current transformer RSILM 1 and 2(4000/5a) which causes the high voltage circuit breaker to trip, if the current taken in by the rectifiers exceeds the setting value of the relays (3600 A).

3. Braking excitation overload relay (QE) The relay QE is fed by means of the excitation current transformer ELM (1000/5 A) which causes the braking excitation contactors C145 to trip out, if the current taken in by the excitation winding of the motor exceeds the setting value of the relays (900 A)

4. Braking overload relay QF-1 and QF-2 The relays of QF 1-2 are connected to the shunts SHF 1-2, which cause the braking excitation contactors C145 to trip out, if the current taken in by braking resistance RF 1 and 2 exceeds the setting value of the relays (700A).

5. Slipping device differential relays QD 1-2 When slip relays of current differential type are provided. When current difference is 125A in between motors 1 and 3 and motors 4 and 6, the relay operates, in case of slipping, it feeds relay Q-48, there by energizing sanding electro valves VESA and sand is applied to corresponding wheels relay Q-51 is also energized causing regression of graduator till the slipping stops.

6. Main circuit earthing relay QOF 1-2 In case of failure of insulation of traction power circuit to earth. The battery supply available to the relay trips the relay through the earth fault and in turn opens the HV circuit breaker DJ.

The switch HQOP 1-2 makes it possible to isolate the relay QOP for 2 and replace it through a resistance RQOP in order to limit the fault current. Now it will be possible to switch on again the circuit breaker DJ in order to bring the locomotive to shed.

7. Traction motor over voltage relay Q-20 Relay Q-20 which is connected via resistance RQ-20 across rectifier output causes buzzer SON 1-2 to work, if voltage exceeds 865v, when voltage falls to740 v, buzzer stops working.

8. No voltage relay or low volts relay Q-30 The relay Q-30 drops out if the single phase auxiliary/winding voltage drops below 215 volts. Its contacts switch off relay Q-44, there by tripping DJ. Relay Q-30 is switched on directly/via the contacts of the relay Q-45 and is fed via resistor RQ-30 after the relay Q-45 opens/drops.

9. Arno starting relay QCVAR Relay QCVAR has been put across ‘w’ phase and neutral of arno to ensure its proper starting. This cuts out arno starting contact for C118. This is English electric relay. It picks up at 155-160 volts a.c.

10. Battery charger signaling relay QV-61 This relay which has been provided across the battery Charging CHBA, indicates the working of the charger. This relay is English electric makes and operates at a voltage of 68-136 v d.c.

PROTECTION AGAINST HALL STORAGE EFFECT

An assembly consisting of a capacitor and a resistor is connected in parallel across each cell. This arrangement prevents dangerous over voltage across the cell which occur upon cut of the commutation. At the same time, these RC- elements also dampen the dangerous over-voltages (surges occurring in the catenary) which may be transmitted to the rectifier via the transformer.

PROTECTION AGAINST OVER-VOLTAGE Over voltage in catenary, which may be transmitted via the main transformer are reduced to a safe value by the following circuit elements

RC-element each consisting of resistor RCAPTFP of 15 ohms in series with a capacitor CAPTFP of 6.25 mfd.

Cathode –drop lighting arrestor ETTFP with a spark over voltage of 5200V.

Capacitors CAPTFP on the secondary winding of the main transformer with an assembly of 12 capacitors 0.5 mfd. Each with center point earthed. These capacitors serve to discharge to earth any over voltage transmitted capacitively.

Further protection of the cells is obtained by the DC damping system for each bridge.

13.WHAT’S THE NEED FOR THE CHANGE?

Presently all the locomotives are using DC traction motors, use of which has following related problems:

The speed /torque regulation is achieved by using either tap changer on transformer or through resistance control on majority of locomotives, where as better speed control techniques are available these days. Moreover, FRPCPY for tap changer and its associated equipments is about 20%.

There are conventional protection and relay schemes to alert the driver. No automatic fault diagnosis is available for the driver. In most of the cases, the driver uses his discretion to get past the problem.

DC motor has inherent problems of brush, gear, commutator and low power to weight ratio. DC motor is essentially a high current low voltage design which calls for expensive large diameter cables and large electro pneumatic reverser, contactors, switches, etc.

Thyristorised DC traction motor drives through make the DC motor drive more efficient, suffer because of high harmonic injection into power supply. Loss associated with large filters had to be carried on locomotives to overcome this. Emphasis on regeneration is increasing day by day to reduce energy bill as well as to save energy for grater national causes.

With ever increasing need for hauling loads, there is need to make

max. use of available adhesion. Whereas, existing DC motor are running on their maximum.

14.ADVANTAGES OF THREE PHASE TECHNOLOGY

1. Three phase traction motor are robust and require little maintenance. Apart from bearings, it has no parts which are subjected to wear and is insensitive to dust, vibration and heat.

2. There is no commutator and so commutator peripheral speed, place no limit on motor speed. AC traction motors can easily operate at 4000 rpm in contrast to DC machines which normally operate at speeds of 2500 rpm.

3. The limitation imposed by bar-to-bar voltage in case of DC commutator motor, is no more a hindrance in case of squirrel cage induction motors. This means that the power flow from transformer to converter to DC link and down to inverter/motor is chosen at higher operating voltages as against nominal system of 750 V, 1000 Amp. With DC machines equivalent three phase propulsion is configured around 2800 V, 300 Amp. Due to heavy reduction in operating current power cables are much lighter and losses are reduced.

4. Power to weight ratio of induction motor is much higher than the DC motor. AS a typical example 1500 KW max. Per axle with h induction motor as compared to 800 KW max. Per axle with DC motors.

WAG 9 WAG 9h

5. Since the torque speed characteristics of induction motor is markedly steeper than that of attained by conventional DC machines, the induction machine can take better advantages of maximum possible tractive effort and a higher mean adhesion coefficient can be expected.

6. As the adhesion coefficient is higher, it is possible to transfer a part of the braking force of the trailing load to electrical braking in the locomotive, i.e. in the case where regenerative breaking is used, the regenerated electric energy can be increased.

7. Almost all moving contactors, switches, relays, reversers are eliminated and operation is sequenced by means of solid state logic.

8. High power/weight ratio of induction motors and reduction in cable thickness, reduction in number of conductors, switches etc. result in reduction in physical dimension and weight of entire system.

9. The induction motor drives are about 20 % energy efficient as compared to DC drives.

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10.Microprocessor control software has flexibility to provide software

based solution to local operational problems.

11.Microprocessor control is used for drive control. The microprocessor allow the redundancy of power equipment, due to built-in controls

12. Microprocessor based fault diagnostic system guides driving crew about the fault location and suggests remedial action. It also keeps records of faults, which can be analyzed by shed staff.

13.Elaborate data-acquisition system along with microprocessor based knowledge bank helps condition monitoring of the equipment and thus assist in condition based maintenance, instead of time based maintenance.

14.Three phase drive allows regeneration and unity power factor operation with low S&T harmonics. Electric braking down to standstill is possible. It improves operational efficiency besides reduction in maintenance efforts. The energy saving due to regeneration and improved power factor sizable.

15.Use to rugged induction motors, reduction in electromechanical contactors, reduction in overall current level, condition monitoring and diagnostic aid, significantly reduce the maintenance effort required and improve reliability in case of three phase locomotives.

To use these advantages of induction motor, it is necessary to supply it with a three phase variable frequency variable voltage. This could not be achieved under technically and economically acceptable condition un till the advent of GTOs and microprocessor based control system in the last few years.

15. ENERGY CONSERVATION IN ELECTRIC TRACTION SYSTEM

Use of gradients for coasting. Level section can also be used for coasting by following proper driving techniques.

Number of scheduled halts/ unscheduled halts and speed restriction should be minimum avoid late lowering of signals control chain pulling.

Talk to engg. Dept. for realignment of track for reduction in length of track ,reduction in curves, reduction in speed restrictions, reduction in gradients etc. these measures may be economical at some locations by taking in to view energy conservation, increased line capacity, reduction in running time and increased availability of rolling stock.

Running at booked speed saves sizeable amount of energy but affects line capacity, promote use of long welded rails for low track resistance. Monitor profile of rail and wheel.

Lubricate outer flange of curved rail for reduction in resistance between rolling stock wheel flange and rail, power factor correction in locos will reduce line losses

Aerodynamic design of loco will reduce air resistance between rolling stock body should be reduced and no projections should be added during maintenance. Reduce the tare weight of coach and wagon.

Driver should be trained for good driving techniques. Provide energy meter to monitor. Release brakes fully before starting. Switch off auxiliaries when not required provide coasting boards at all suitable locations.

Switch of electric locos when idle more than 45 minutes. Avoid running of trains via loop. Do not run trains with out guards as speed

Restrictions are to be followed. Control brake binding in rain. Improve brake power of train. Carry goods via shortest route.

Avoid use of resistance in locomotives. Use tube lights and FRP fan blades in EMU/coach/locos

Use efficient speed control methods. Do not use resistance for speed control. Thyristor control, chopper control and 3 phase technology with frequency control etc can be useful.

Use regenerative braking.

Avoid running of light locos. Reduce running of dead locos. Repair in nearest loco shed. Reduce running of empty rakes. Reduce running of EMUs on holidays.

Power factor : induction motor, welding transformer, florescent tubes, induction furnaces etc, are the main sources of low power factor. Use capacitor to improve power factor. Because this reduce maximum demand charges based on KVA, reduce line losses and improves voltage.

Reduce material handling need by proper layout of working section in sheds.

Control leakages of water, gas, air, electricity etc.

Lubricate motors pumps etc, periodically. Maintain the equipments periodically for running at high efficiency. Dust, grease etc, cause poor heat/light transfer and hence causes poor efficiency of motor, condensers, intercoolers, light sources etc. control idle running of machines.

Train and award staff for energy conservation measures. Display energy conservation board.

Review existing installation for latest design, location etc. and do energy audit.

Measure and monitor energy consumption at different machines, sections, etc. this will help in knowing efficient machines, section etc. appoint energy managers for auditing energy.