REQUIREMENT OF AN IDEAL TRACTION SYSTEM
WHY ELECTRIC TRACTION SYSTEM??
LEADING TRACTION SYSTEMS AROUND THE WORLD
ELECTRIC TRACTION SYSTEM
Driving forward of vehicle is called traction and the system, which employs this
type of mechanism is called Traction system.
Classified broadly into groups namely:
Non-Electric traction system:
Traction system which do not involve the use of electricity such as steam engine
drive, IC engine drive etc .
Electric traction system.
The system which use electrical power for traction system i.e. for railways,
trams, trolleys, etc. is called electrical traction.
ELECTRICAL TRACTION SYSTEM
Electric traction is meant for locomotion in which the driving (tractive) force
is obtained from electric motors(called as traction motors).
The first known electric locomotive was built in 1837 by
chemist Robert Davidson of Scotland. It was powered by
galvanic cells (batteries).
In 1880, Thomas Edison built a small electrical railway,
using a dynamo as the motor and the rails as the current-
TYPES OF ELECTRIC TRACTION SYSTEM
POPULARLY PRACTISED VOLTAGE
25KV,50HZ 1500V &3000V DC
1.5kv DC, 3kv DC , 1.5kv AC, 25kv AC
1-TRACTION SUBSTATION 2-OVERHEAD WIRING
3-CURRENT COLLECTOR 4-TRACK
5-TRACTION SYSTEM (VEHICLE)
MAJOR COMPONENTS CNTD…
AC Circuit Breaker
DC Circuit Breaker
Transformers & Rectifiers
Transfer to required voltage level and Rectification.
Control and Monitoring unit
Typically 4km to 15km
Depends on a number of factors including
• Train loads
• Track grades
• Over head wiring types
• 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 catenary.
• Two different types of catenary construction can be used-
One or two contact wires supported by a catenary wire
A main catenary supports an auxiliary catenary, which in
turn supports the contact wire.
MAJOR COMPONENTS CNTD…
5-TRACTION SYSTEM ( VEHICLE)
CIRCUIT BREAKERS: To disconnect the engine (motor)
in case of some fault
TRANSFORMER: Tap changing transformer is installed
in the locomotive for stepping down the voltage according
to the requirement of the traction motor.
ON LOAD TAP CHANGER: Used for varying the
output voltage for controlling the speed of motor.
RECTIFIER AND SMOOTH REACTORS:
Semiconductor rectifier are used for AC to DC power
conversion. Smooth reactors eliminates ripples found on
output side of rectifier.
MAJOR COMPONENTS CNTD…
TRACTION SYSTEM ( VEHICLE) CNTD…..
D.C series motors:
Single phase A.C series motors:
Three-phase Induction motors
High torque at low speeds & low torque at high speeds.
Easy speed control
Speed of an ac series motor may be controlled efficiently by taps on a transformer
Trouble free operation
Less maintenance requirement
complicated speed control systems
Not suitable for traction work
Automatic regeneration is the main advantage of this motor
REMOTE CONTROL CENTER(RCC):
From substation/ Traffic control division
Nerves system for traction system.
3 Pair of conductors from and to RCC
SYSTEM CONTROL CENTER:
Master controller ,From the vehicle
Enable output from the vehicle
Forward, reverse, powering, neutral and
braking, to the electric control device
REQUIREMENT OF IDEAL TRACTION
Maximumtraction effortsshouldbeexertion atstartinginordertohaverapid
Capacityofwithstanding voltagefluctuation andtemporaryinterruption of
Brakingshouldbepossible withoutexcessive wearonthebrush.
Parallel running usually more thanonemotor(twoorfour)shouldbepossible.
 Traction transformer
 Traction control
 Traction motor
 Auxiliary converter
 Energy storage
 Traction convertor
 Control and Monitoring System
 Diesel engine generator
 Battery charger
BRAKING OF ELECTRIC TRACTION
BRAKING CAN BE ACHIEVED BY TWO METHODS-
ELECTRICAL BRAKING very superior then MECHANICAL BRAKING
CLASSIFIED INTO THREE CATEGORIES-
1.PLUGGING- Plugging is applied by changing phase sequence of synchronous or
2.RHEOSTATIC BRAKING- Connection are made changed from power configuration to
brake configuration and resistor are inserted in motor circuit.
3.REGENERATIVE BRAKING- Motors become generators and feed resulting current
back into supply system.. Return current, generated during braking, to the supply system for use by
WHY ELECTRIC TRACTION SYSTEM???
Maintenancecost: 50%less then othersteamengines
Startingtime and speed:Withoutlossoftime.
Braking : Regenerativebreakingisusedwhichfeedsbackenergy.
LEADING TRACTION SYSTEMS AROUND THE WORLD
Magnetic traction (maglev).
Speeds up to 581 kmph have been successfully
Shinkansen (bullet train) uses electrical system,
offering high acceleration and deceleration.
It employs an automatic train control system
(atc),which controls all train movements ,track
,station and schedule are networked and
Software Analysis and Modelling (etrax)
LONGEST ELECTRIC TRACTION SYSTEM
OUR NEIGHBOURS CHINA AND INDIA ARE
IN 3RD &4 TH POSITION.
Don’t we bear the potential??
Yes, of course!!!!!
Past electric trolly bus
Present status of
electric trolly bus
Started in 1975 - gift by the government of the People's Republic of China.
13km - 10,000 passengers daily
Route: Tripureshwor Ktm – Suryabinayak Bhaktapur
Tripureshwor – Koteshwor
Suspended in 2008
Permanently dismissed in 2009 by KMC due to chronic unprofitability.
DC: Use DC from overhead line. The most popularly practised voltage 1500v &3000v DC.
AC: Draw ac from overhead line. Typical voltage used are 25kv,50Hz.
Multisystem: Locomotion can be changed from switching substation (AC/DC). In Europe: It is common to use four system locomotives( ie.1.5kv DC,3kv DC , 1.5kv AC,25kv AC ).
Ac or dc.. Which one is superior!!!
Isolatoer operates on no load condition (manually operated) Cb on load n unload condition (automatic and manuall operaton)
Generally used 25kv 12.5mva heavy load
A.TROLLY COLLECTOR Used for tramways and trolley buses. Held in contact with wire and spring Suitable for low speeds 32 kmph B. 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.
C. PANTOGRAPGH 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.
Lighting arrestors are provided to protect every sub-sector against voltage surges. Auxiliary transformers are provided at all the posts and also at certain intermediate points to supply AC at 240 V, 50 HZ required for signaling and operationally essential lighting installations. To ensure fairly steady voltage, automatic voltage regulators are also there, where required. Potential transformers are provided at the various switching stations for monitoring supply to each sub-sector. A small masonry cubicle is provided to accommodate remote control equipment, control panel, telephone and batteries and battery chargers required for the control of interrupters and the similar equipments.
DC: This motror meets the requirement of traction units exactly.
AC:Easier construction than of a dc series motor. Starting torque of a.c single phase motor is lower than that of dc series motor due to poor power factor at the start but speed of an ac series motor may be controlled efficiently by taps on a transformer which is not possible in case of a dc series motor
3 phase:Various advantages like simple and robust construction ,trouble free operation, less maintanaince requirement can be obtained but due to their flat speed- torque characteristics, constant speed operation, developing low starting torque, drawing high starting current, complicated speed control systems they are not suitable for electric traction work
Remote control :Under ground telecommunication trunk cable is provided for transmitting the signals from and to the Remote Control Centre (RCC) and the controlled Remote Terminal Units (RTU). Three pairs of conductors (one pair for send one pair for receive and the third as spare) from this cable are made available for remote control operation. (RCC) is set up near the traffic control office on each division having electric traction to work in close liaison with the traffic control.
In this content we hav include the major characteristics of electric traction system to hav maximum efficiency first of all, lets us discuss about wears on track 1* Due to heavy load unbalce pressure may exert on the track which may reduce lifespan of the track so wear should b minimized By designing various mechanical system..
2 *at starting to have rapid acceleration traction motor should be able to exert maxium traction effort for this DC motor is a perfect choice. But AC series motor are prefered in order to reduces the possiable fault.
3*In the system ther may arise condition of overload so our system should be capable to withstand those overload for certaion periods…. For this size of conductor and rating of equipement should be slightly greater than marginal value.
4*A traction system shouldn’t stop due to tempory inturruption of the supply . It should be capable to withstnd some voltge surge and fluctions tooo.For this system should hav other suppy scheme. We can hav a diesel generator or any other energy supply scheme
5*In case of breaking there shouldn’t be excessive pressure on the brushes and other component of the system. To reduce this excessive pressure electrical breaking is preferred over mechanical braking. 6*In oder to hav similar operation for all motor motors can be operated in parallel , our system should rum 2 or more motors parallely
Why electrical are superior than mechanical????? HIGH WEAR AND TEAR NON UNIFORM BREAKING LOSS OF ENERGY
And discuss the advantage of regenerative type… Alternation of phase sequence rotate motor in opposite direction.acts as a break
Rheostatic breaking:When operator call for brake power circuit connection are made changed from power configuration to brake configuration and resistor are inserted in motor circuit. Then the energy id dispersed in resistor and train slows down.
Regenerative:. The motors become generators and feed the resulting current back into the supply system a train could use its motors to act as generators and that this would provide some braking effect if a suitable way could be found to dispose of the energy. Trains were designed therefore, which could return current, generated during braking, to the supply system for use by other trains.
COMPARE TO DIESEL ENGINE Cheapness : It is cheapest method than other methods of traction. Cleanliness : It is free from smoke and fuel gasses. Maintenance cost : Maintenance and repair cost is about 50% of steam traction system. Starting time : It can be started without loss of time. High starting torque : This system uses of D.C & A.C series motor, which has a very high starting torque. Braking : In electric traction, regenerative breaking is used which feeds back 40% of the energy. Saving in high grade coal : No coal is required for electric traction.
Disadvantages: (a) Electric traction has high initial cost of laying out overhead electric supply system. (b) Power failure for few minutes can cause traffic dislocation for hours. (c) Communication lines which usually run parallel to the power supply lines suffer from electrical interference. (d) Electric locomotive can be use only on those routes which have been electrified.
DIS:EXPENSIVE SUBSTATIONS ARE REQUIRED AT FREQUENT INTERVALS AND OVERHEAD LINE OR THIRD RAIL MUST BE RELATIVELY LARGE OR HEAVY.
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 deceleration. It employs an automatic train control system (atc),which controls all train movements ,track ,station and schedule are netwoked and computerized.
PRESENT CONTEXT From the chart we can see that our neigbours china nd india are the 3rd and 4th country to have electric traction system
In Nepal The trolleybus system was opened in 1975, by way of utilizing technical expertise and a grant of 40 million Nepali Rupees, provided as a gift by the government of the People's Republic of China. 13 km. trolleybus line connected Kathmandu and the satellite towns of Madhyapur Thimi and Bhaktapur to the east of the Capital. seven year ago in 2009, the Kathmandu Metropolitan City (KMC) decided to permanently shut the trolleybus operation and dissolve the undertaking All assets were sold to private entities. Oner head transmission line wire were removed during widining of Araniko highway.. Serves 10,000 passengers daily in that time.
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