Future Trends in Technology for Locomotive Traction

Future Trends in Technology for Locomotive Traction

SYNOPSIS

Eventual migrations of D.C. tractions system has let the use of Microprocessor and power electronics devices for starting and control operations D.C. motors. Motor are afforded in tractions system for superior speed and starting control. Replacing these D.C. motors by three phase A.C. motor with frequency and voltage control will reduce the current requirement at good power factor and better efficiency.

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1.INTRODUCTION Act of drawing or state of being drawn propulsion of vehicle is called tractions. And the system of tractions involving the use of electricity is called the electric tractions. There are various system of traction prevailing in our country such as steam engine drive, electric drive. These system of tractions may be classified broadly in to groups namely 1) The tractions system which do not involve the use of electricity at any stage and called the non-electric tractions system such as steam engine drive IC engine drive. etc. 2) The tractions system which involves the use of electricity at same stage or the other and called the electric tractions. System such a diesel electric drive, electric drive etc. Electric tractions was first introduced by British railway in 1890 at 600 V D.C. Using a third rail system. Because of fraught with danger to life this system was not considered desirable. This operating voltage was increased form 1.5 KV D.C. to 3 KV D.C. and then to 25 KV A.C. up to 1959. Finally 1959 the first actual train run by using 25 KV A.C. Hence India took the phinge from 600V D.C. to 25KV A.C. electric tractions up to 1960 which uses D.C. tractions motor. A step ahead this paper gives use of three phase inductions motor as a tractions motor.

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2.ELECTRIFICATION OF TRACTIONS MOTOR In India first electrifications was under taken during 1925 to 1952. Transmissions of power through A.C. lines is always along the traction by means of an over head wire. Overth collector with certain advantages uses the pentograph collector. In India electrification are conducted with 4 types of locomotives. 1. Using single phase A.C. series commutator motor. 2. Using D.C. motor from tapped transformer and rectifier. 3. Using grid control on rectifier. 4. Using phase converter and inductions motor.

EXISTING TRACTIONS SYSTEM Existing tractions system uses D.C. motors. The 25 KV over head collector is step down to 2000V with the help of step down transformer. Rectifier rectifies this A.C. voltage to D.C. voltage. This rectified D.C. voltage is used to operate the D.C. motors in existing system engine are use for the good trains and the passenger train heavier load on good trains, motor are started at a reduced achieved with the help of gear mechanisms and thus train gradually. Also the disadvantages of D.C. series motor used in system.

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1)

D.C. series motor are less costly however for some H.P. more efficient and requires less maintenance than A.C. series motor.

2)

A.C. system has interference than A.C. series motor and A.C. system has high interference with communications lies than D.C. system.

3)

Rail conductor system of track electrifications which is less costly, is possible with D.C. system than with A.C. system.

4)

A.C. system produces unbalanced supply system of two types a) Current unbalanced b) Voltage unbalanced

5)

D.C. motors commutator which are prove to failure because of vibrations and shock. This results in lots of sparking and corrosion.

6)

It is hard to use a D.C. motor for regenerative breaking and for purpose and extra switchgear is required, which adds to the bulks and increases the complexity of the locomotives. So that’s why it becomes necessary to think on these disadvantages.

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g Generatin

Station

Grid Substation

Tractions Substations

OHE

Feeding Post

Pentograph

DJ

Traction s motor

Smoothi ng

To neutral

Rectifi er

Transf ormer

Auxilliary equipment

Railway track

Block diagram of 25KV A.C. locos

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On load tap changer


3.FUTURE TRENDS FOR INDIAN RAILWAY SYSTEM This short coming from this overcome by using three phase A. C. motor in locomotive microprocessor technology and availability efficient and compact power components have give a new technology for A.C. locomotive. In three phase A.C. locos. The single phase input signal from overhead equipment is rectified then three phase, A.C. is generated with the help of three phase inverter. Whose phase voltage and frequency can be manipulated widely. The three phase induction motor are simple and robust in construction and have a high operating efficiency and properly of automatic regenerative breaking with requiring additional equipment. There are three main stages in power circuit of three phases locomotive.

1) Input converter This rectifies AC from catenary to as specified de voltage using GTO thyristors. A transformer section stepdown the voltage from the 25 KV input. It has filter and circuitory to provide a fairly smooth and stable dc output, at the some time attempting to ensure good power factor. The input converter can be configured to present different power factor to power supply.

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25 KV Overhead line Pantograph

C.B 25 KV/200V

Rectifier Circuit Filler circuit

Filler circuit

Axle Brush Power circuit using D.C. traction motors

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25 KV overhead line Pantog rap h

Main Auxiliary Circuit

Three phase AC motors

Inverter

Main transformer

Axle brush

Power circuit using A.C. traction motors

2) DC link Govt. Poly. Washim

A.C. motor


This is essentially a bank of capacitor and inductor or active filter circuitory to further smooth. The DC from previous stage and also to trap harmonies generated by drive converter and traction motors. The capacitor bank in this section provides a small amount of re- serve power in transient situations.

3) Drive converter This is basically an inverter which consist of three thyristors based components that switch on and off at precise times under the control of a microprocessor. The three components produce three phase of A.C. The microprocessor controller can vary the switching of thyristors and there by produce A.C. of wide range of frequency and voltage.

4.USE OF INSULATED GATE BIPOLAR TRANSISTOR IN CONVERTER (IGBT'S) Govt. Poly. Washim


IGBT's provides nigh switching speeds for finer control over the waveforms generated instead of GTO'S, IGBT is can he used because of following advantages. 1) It does not need high current for turned "ON" and "OFF". 2) It can handle 1000 Amp. of current and can be used for train application. 3)

It can switched faster as compared to GTO'S.

4) Current required for IGBT'S is small and therefore heat generated is smaller and it uses smaller and lighter unit.

5.ADVANTAGES OF 25 KV A.C. LOCOS

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1)

Three Phase Induction AC motor do not use commutator.

2)

Trouble free operation.

3) Less maintenance. 4)

High Voltage operation needed reduce amount of current.

5)

Automatic regenerative braking is applied.

6)

Because of simple construction, the rotor can resist better centrifugal forces then that of D.C. motors.

7)

As it draws small current. Copper less get reduced and more power can be produced. Hence efficiency in high.

8)

Good overall power factor.

CONCLUSION From the above study it can be conclude that :

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The performance of A.C. Railway traction system is quite satisfactory. They offer varies advantages over the other traction system such as steam engine drive, I.C. engine drive , diesel engine drive etc. As we know that reservoirs of coal and mineral oils are scantly, the use of steam engine and diesel is limited and unprofitable considering the fuel cost. So the A.C. railway proves very precious thing and gives very satisfactory performance as compared to other traction system. 1)

Use of AC locomotives provides a better operation in traction system then that of D.C. locos.

2)

Use of Insulated gate bipolar transistor improves the starting of D.C. locos.

REFERENCES

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1) Modern electric traction - H. Pratab

2) Traction manual book - Bhusawal training institute of railways

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Future Trends in Technology for Locomotive Traction

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