ELECTRIC TRACTION

SYSTEMSUBMITTED BY-HARMANJEET SINGHROLL NO-12264SUBMITTED TO-Dr O.P RAHIDr NAVEEN SHARMA

ELECTRIC LOCOMOTIVES

ELECTRIC TRAINS RAPID TRANSIT SYSTEMS

CONTENTS INTRODUCTION TYPES OF TRACTION SYSTEMS ELECTRONIC SPEED CONTROL METHOD OF DC MOTOR PULSE WIDTH MODULATION AC TRACTION SYSTEMS MERITS AND DEMERITS OF VARIOUS METHODS BRAKING OF TRACTION SYSTEMS AUXILLIARY EQUIPMENTS RECENT TRENDS IN ELECTRIC TRACTION CONCLUSION INDIAN RAILWAY AND CAREER OPTIONS IN INDIA AND ABROAD REFERENCES

INTRODUCTIONELECTRIC TRACTION IS MEANT FOR LOCOMATION IN WHICH THE DRIVING (TRACTIVE) FORCE IS OBTAINED FROM ELECTRIC MOTORS(CALLED AS TRACTION MOTORS).FOR TRACTION MOSTLY 3 PHASE INDUCTION MOTOR AND DC MOTOR IS USED ,BOTH HAVE HIGH INITIAL TORQUE,PREREQUISITE FOR HIGH SPEED ACCELERATION.

TYPES OF ELECTRIC TRACTION SYSTEMS

DC TRACTION AC TRACTION MULTI SYSTEM

DC TRACTION

DC TRACTION USES DIRECT CURRENT DRAWN FROM EITHER FROM A CONDUCTOR OR OVERHEAD LINES.

MOST POPULAR LINE VOLTAGES FOR OVERHEAD SUPPLY SYSTEM-1500V DC AND 3000V DC

600V DC-750V DC VOLT RANGE IS USED FOR THIRD RAILSYSTEMS (ADDITIONAL RAIL IS PROVIDED FOR SUPLLYING ELECRTRICITY TO TRAIN AND IS CALLED CONDUCTOR RAIL)

DC TRACTION USING SEPEX (ELECTRONIC CONTROL)

DISADVANTAGES-

EXPENSIVE SUBSTATIONS ARE REQUIRED AT FREQUENT INTERVALS AND OVERHEAD LINE OR THIRD RAIL MUST BE RELATIVELY LARGE OR HEAVY.

PULSE WIDTH MODULATION

MAIN PRINCIPLE IS TO CONTROL ELECTRIC POWER BY VARYING POWER.

CONDUCTION TIME TO LOAD IS CONTROLLED.

THE OUTPUT FROM THE THYRISTOR VARIES FROM 0 TO MAXIMUM IN PERIOD T.

AC TRACTION• AC TRACTION UNITS DRAW ALTERNATING CURRENT FROM AN

OVERHEAD LINE.• TYPICAL VOLTAGES USED ARE- 15 KV, 16.7 HZ 25 KV, 50 HZ 25 KV, 60 HZ• FEWER SUBSTATION REQUIRED AND LIGHTER OVERHEAD CURRENT

SUPPLY WIRE CAN BE USED.• REDUCED WEIGHT OF SUPPORT STRUCTURE.• REDUCED CAPITAL COST OF ELECTRIFICATION.

AC MOTOR TRACTION

MULTI SYSTEMS• BECAUSE OF VARIETY OF RAILWAY ELECTRIFICATION SYSTEMS, WHICH

CAN VARY WITHIN A COUNTRY TRAINS HAVE TO PASS FROM ONE SYSTEM TO ANOTHER.ONE WAY TO ACCOMPLISH THIS IS BY CHANGING LOCOMOTIVES AT THE SWITCHING STATIONS.

• THESE STATIONS HAVE OVERHEAD WIRES THAT CAN BE SWITCHED FROM ONE VOLTAGE TO ANOTHER AND SO TRAIN ARRIVES WITH ONE LOCOMOTIVE AND THEN DEPARTS WITH ANOTHER.

• OFTEN THIS IS INCONVINIENT AND TIME CONSUMING .ANOTHER WAY IS TO USE MULTI SYSTEM LOCOMOTIVES THAT CAN OPERATE UNDER SEVERAL DIFFERENT VOLTAGES AND CURRENT TYPES.

• IN EUROPE ,IT IS COMMON TO USE FOUR-SYSTEM LOCOMOTIVES(1.5 KV DC,3 K.V DC,15 K.V 16.7 HZ AC,25 KV 50 HZ AC)

ADVANTAGES OF AC TRACTION SYSTEMS• HIGHER POWER TO WEIGHT RATIO.• RESULTS IN- FASTER ACCELERATION HIGHER PRACTICAL LIMIT OF POWER HIGHER LIMIT OF SPEED HIGHER HAULING CAPABILITY• NO EXHAUST FUMES OR CARBON EMISSIONS.• LESS NOISE POLLUTION.• MAINTAINANCE COST LESS THAN DIESEL AND DC TRACTION.• NO INITIAL HEATUP TIME REQUIRED CAN BE USED IMMEDIATELY AFTER

STARTING.• HIGHER STARTING TORQUE ABOUT(1.5 TO 2.5 KM/H/S).

ADVANTAGES CONTINUED-• IT IS POSSIBLE TO USE REGENERATIVE BRAKING ON TRACTION

SYSTEM.IT LEADS TO FOLLOWING ADVANTAGES- ABOUT 80 % OF ENERGY TAKEN FROM THE SUPPLY DURING ASCENT IS

RETURNED TO IT DURING DESCENT.AND PRESENTLY IT IS MADE AVAILABLE TO OTHER VEHICLES ON NETWORK.

• SINCE HEIGHT OF ELECTRIC LOCOMOTIVE IS MUCH LESS THAN COUNTERPARTS THIS ENEBLES LOCOMOTIVE TO TAKE CURVES AT HIGHER SPEEDS.

• NO WEIGHT OF FUEL NEED TO BE CARRIED LIKE(COAL OR DIESEL LOCOMOTIVE).

• FULLY UNIFORMLY ELECTRIFIED RAILWAY DON’T NEED SWITCHING ,MAKING OPERATIONS MORE EFFICIENT. SWITZERLAND USES THIS.

DISAVANTAGES AC TRACTION SYSTEMS

• SIGNIFICANT COST OF ELECTRIFICATION.• INCREASED MAINTAINANCE COST OF LINES.• OVERHEAD WIRES FURTHER LIMIT CLEARANCE IN TUNNELS.• UPGRADING NEEDS ADDITIONAL COST ESPECIAALY IN CASE THERE

ARE BRIGDES AND TUNNELS.• RAILWAY TRACTION NEEDS IMMUNE POWER WITH NO CUTS.

SYSTEM OF TRACK ELECTRIFICATION

AUXILLIARY EQUIPMENTS

CATENARY CURRENT COLLECTORS CIRCUIT BREAKERS ON LOAD TAP CHANGERS TRANSFORMER RECTIFIERS SMOOTHING REACTORS

• TYPES OF SYSTEM ELECTRIFICATION• TROLLEY WIRE OR CONTACT WIRE-SUSPENDED WITH MINIMUM OF

SAG SO THAT CONTACT BETWEEN THE TROLLEY WIRE AND CURRENT COLLECTOR CAN BE MAINTAINED AT HIGHER SPEEDS.

• THE WIRE IS SUPPORTED BY ANOTHER WIRE CALLED AS CATERNARY.

• TWO DIFFERENT TYPES OF CATERNARY CONSTRUCTION CAN BE USED-

SINGLE CATENARY COMPOUND CATENARY

SINGLE CATENARY CONSTRUCTION

CURRENT COLLECTORS

CURRENT FROM THE OVERHEAD LINE IS COLLECTED WITH THE HELP OF A COLLECTOR FIXED ON THE ROOF OF THE VEHICLE.

TYPES OF COLLECTORS-1. TROLLEY COLLECTOR2. BOW COLLECTOR3. PANTOGRAPH COLLECTOR

TROLLEY COLLECTOR

• USED FOR TRAMWAYS AND TROLLEY BUSES.

• HELD IN CONTACT WITH WIRE AND SPRING

• SUITABLE FOR LOW SPEEDS 32 KMPH

BOW COLLECTOR• IT USES A METAL LIGHT STRIP

OR BOUGH FOR CURRENT COLLECTION ABOUT ONE METRE LONG.

• NOT SUITABLE FOR RAILWAY WORK REQUIRING SPEEDS MORE THAN 120 KMPH.

• REQUIRES REVERSING ARRANGEMENT OF BOW.

PANTOGRAPH COLLECTOR• MAIN FUNCTION IS TO

MAINTAIN THE LINK BETWEEN OVERHEAD CONTACT WIRE WIRE AND THE POWER CIRCUIT OF THE LOCOMOTIVE AT VARIOUS SPEEDS IN DIFFERENT CLIMATE AND WIND CONDITIONS.

• THIS CAN BE LOWERED OR RAISED FROM CABIN WITH THE HELP OF CONTROLLING CYLINDERS.

TRACTION MOTORS DC MOTORS- DEVELOPS HIGH TORQUE AT LOW SPEEDS AND LOW TORQUE AT HIGH

SPEEDS EXACT REQUIREMENT OF TRACTION SYSTEMS. TORQUE IS INDEPENDENT OF LINE VOLTAGE THEIRFORE UNAFFECTED BY VOLTAGE FLUCTUATIONS

SINGLE PHASE AC MOTORS- STARTING TORQUE LESS THAN DC MOTOR BUT SIZE AND COST

CONSIDERABLY LESS.MAXIMUM OPERATING VOLTAGE IS 400V. THREE PHASE INDUCTION MOTORS- PROVIDES CONSTANT SPEED OPERATION,DEVELOPING LOW

STARTING TORQUE DRAWING HIGH STARTING CURRENT AND COMPLICATED CONTROL MAKES IT UNSUITABLE FOR TRACTION WORKS.

AUTOMATIC REGENERATION IS THEMAIN ADVANTAGE WITH THIS MOTOR

BREAKING OF TRACTION BASED TRAINS BREAKING CAN BE ACHIEVED BY TWO METHODS-1. MECHANICAL BREAKING2. ELECTRICAL BREAKING IN CASE OF ELECTRIC TRACTION SYSTEM ELECTRICAL BREAKING IS

USED MAINLY ALONG WITH MECHANICAL BREAKING.MECHANICAL BREAKING HAS FOLLOWING DISADVANTAGES-1. HIGH WEAR AND TEAR2. NON UNIFORM BREAKING3. LOSS OF ENERGY DUE TO ABOVE SAID DISADVANTAGES ELECTRICAL BREAKING IS

USED.

ELECTRICAL BREAKING DYNAMIC BRAKING-WHERE MOTORS BECOME GENERATORS AND

FEED THE RESULTING CURRENT BACK. CLASSIFIED INTO THREE CATEGORIES-1. PLUGGING2. RHEOSTATIC BRAKING3. REGENERATION PLUGGING- PLUGGING IS APPLIED BY CHANGING PHASE SEQUENCE

OF SYNCHRONOUS OR INDUCTION MOTORS. RHEOSTATIC BREAKING- MOTORS BECOME GENERATORS AND FEED

RESULTING CURRENT BACK INTO ONBOARD RESISTANCES. REGENERATIVE BRAKING- MOTORS BECOME GENERATORS AND FEED

RESULTING CURRENT BACK INTO SUPPLY SYSTEM.

LEADING TRACTION SYSTEMS AROUND THE WORLD NOWADAYS MAGNETIC TRACTION IS BEING USED IN TRAINS

(MAGLEV). SPEEDS UPTO 581 KMPH HAVE BEEN SUCCESSFULLY TESTED. SHINKANSEN (BULLET TRAIN) USES ELECTRICAL MULTIPLE UNIT

STYLE,OFFERING HIGH ACCELERATION AND DECELARATION. USES 25000 VOLTS OVERHEAD LINE. IT EMPLOYS AN AUTOMATIC TRAIN CONTROL SYSTEM (ATC),WHICH

CONTROLS ALL TRAIN MOVEMENTS ,TRACK ,STATION AND SCHEDULE ARE NETWOKED AND COMPUTERIZED.

INDIAN RAILWAY 4TH LARGEST NETWORK. EMPLOYS 1.6 BILLION

PEOPLE. CONSUMES ONLY 1.7% OF

TOTAL OIL CONSUMPTION OF INDIA ,LARGELY DEPENDENT ON TRACTION UTILITY.

CONCLUSION

NO SINGLE MOTOR IS IDEAL FOR TRACTION WORK BUT DC SERIES MOTOR IS MOST SUITABLE FOR ELCTRIC TRACTION.

POWER ELECTRONICS HAS BEEN RESTORTED TO IN A MAJOR WAY FOR CONVERSION AND CONTROL OPERATIONS.

DIFFERENT TYPE OF BREAKING WERE DISCUSSED OUT OF WHICH REGENERATIVE IS MOST EFFICIENT.

IDEAL TRACTION SYSTEM SHOULD BE ABLE TO-1. WITHSTAND SMALL VOLTAGE FLUCTUATIONS AND OVERLOADS FOR

SMALL PERIODS.2. BRAKING SHOULD BE WITHOUT EXCESSIVE WEAR AND TEAR.3. PARALLEL RUNNING(MORE THAN ONE MOTOR) SHOULD BE POSSIBLE.

REFERENCES-

FUNDAMENTAL OF ELECTRIC DRIVE BY(G.K DUBEY) WIKIPEDIA (ELECTRIC TRACTION AND HIGH SPEED TRAINS) INDIAN RAIWAY OFFICIAL WEBSITE POWER ELECTRONICS BY (P.S BHIMBRA)

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