Conventional Indian Railways and the Advanced Transportation Systems: A Comparative Review V. Shirish Murty Shailendra Jain Student Member, IEEE Research Scholar, MANIT, Bhopal firstname.lastname@example.org Senior Member, IEEE Prof. EE. Dept., MANIT, Bhopal email@example.com Abstract— This paper presents the concepts of conventional electric traction system and the advanced transportation systems adopted for research and commercialization in Indian railways. A comparative study is presented on Conventional systems, Metro transit, Pendolino trains, Talgo transit system and Maglev technologies. The principle requirements, control mechanisms, merits and demerits of electromagnetic schemes of maglev systems are also presented. Static and dynamic model explanation is given to propose the control mechanism for the development of High Speed Transit System with Maglev effect. Keywords— Electric traction system, Metro transit, Pendolino trains, Talgo Transit system, Magnetic Levitation, High speed transit system, Linear motors. I. INTRODUCTION With the increase in traffic density in the developing countries, like India, the transit systems like automobiles and air services are unable to provide the required load of mass transit. In order to meet the demand, the transit system should be convenient, high speed, eco friendly, maintenance free, reliable, safe and suited to bulk transportation [1,2]. Reduction of transport associated pollution, and a more comfortable and efficient transportation in respect of both the ride quality and improved speed, is the primary motivation. A novel technology that brings all the advantages of high speed transportation system, such as the Maglev without the exorbitant cost is the demand of the scenario. In earlier days, direct current motors were used. Bad commutation, high initial and maintenance cost has became the major disadvantages of the DC motors. Later on AC induction machines were launched in the field of traction. Due to their fixed speed characteristics, they were difficult to apply for traction applications . One of the best solutions to fulfil the above requirements is Magnetic Levitation (Maglev) trains [1,5]. Conventional railway locomotives moves by utilising friction between rails and wheels but the Maglev trains have electromagnets in place of wheels. It levitates on the guideway and produces propulsion force electromechanically without having any physical contact . In this paper, the concepts of conventional electric traction system and the advanced transportation systems such as Metro transit, Talgo system and High speed Maglev transit system, 978-1-5090-4530-3/16/$31.00 ©2016 IEEE have been presented. The suitability of such advanced transit systems for research and commercialization in Indian railways has also been discussed. A study on the static and dynamic modeling of the locomotive which will be useful for the implementation on high speed transit systems is analyzed. The need of linear motors in practical scenario and their various practical applications are also included. Using finite element method the magnetic performance of the proposed Linear motor is demonstrated. II. CONVENTIONAL INDIAN RAILWAYS The Indian rail is considered to be the single largest user of the electrical power in the country. It has one of the largest rail networks in the world [2-4]. It has a large fleet of trains, which includes diesel and electric engines, and a requirement of a high capacity of transportation for passengers and goods. Its passage through huge sections of forests and its impact adversely affects these forests . Curbing the consumption of fuel per ton per mile by the railways, would have substantial environmental impact and would be single greatest contributor for energy conservation. There are many factors which hurdles in increasing the speed of trains [3,4]. These are as follows1. Old technology and infrastructure, which are still using track building and other subtle foundation of the infrastructure. 2. Poor coupling technique which decreases the stability and permit of high speed transportation. 3. Longer length of trains to cater large number of passengers and inability of heavy loading of goods in transportation. 4. Unreliable tracks, in some sections trains can’t even touch 100 km/h speed falling against the dream of achieving 200250 km/h. 5. Economy does not support investment in new infrastructure. 6. Potential commuters constitute very less percentage as compared to current number. 7. Large distance between major cities. Our present technology is sufficient to cross the threshold of 200 km/hr, as seen on Delhi-Agra section [3-5]. The system can be made more reliable by having solid track foundation, improved coupling system and by decreasing length of trains. A detailed scenario of the electric traction system in Indian railways is explained in the next section. A. Electric traction system Electric locomotive is a vehicle that can move along rails and push or pull a train attached to it using electric power drawn from overhead lines. This power is extracted from overhead lines and then transformed and modified before feeding it to traction motors. compared to AC motors . But, with an advent of highly robust and flexible 3 phase AC machines , the DC motors are almost replaced with AC motors [4,5]. Locomotives uses 3 phase induction motors, though the speed torque curve of induction motor is flat, but better speed control is achieved by supplying A.C. of varying frequency as shown in Fig.1. B. Metro Trains which functions as a means of transportation within a particular city are generally termed as Metro trains, which is shown in Fig. 2. They are faster and are light weight plus have high more horsepower per ton (15 kW/ton) as compared to conventional (5-10 kW/ton) . Base of track is also solid which results in decreased vibrations and stable and smooth ride. It employs polyphase induction motor for traction. Fig. 1 Conventional Electric railway locomotive  For modifying, the present system, it uses a number of components which carry out the complicated processes of conversion, reconversion, smoothening and transformation of the current, voltage and frequency . The parameters of locos WAP 5, WAP7 and WAG9 are shown below in Table 1. Table 1: Mechanical and Electrical parameters of Locomotives  PARAMETER WAP5 WAP 7 WAG9 GEAR RATIO 1:3.65 1:3.6 1:5.133 WEIGHT 78 TONNE 123 TONNE 123 TONNE OHE VOLTAGE NORMAL MAX. MIN. 25kV 30kV 17.5kV FREQUENCY NORMAL MAX. MIN. 50 Hz 55 Hz 45 Hz NO. Of TRACTION MOTORS 4 VOLTAGE TO TRACTION MOTOR 6 Fig. 2 Metro transit system  The requirement of a train working as metro is high starting torque, high acceleration and high deceleration. It should start faster, accelerate fast to reach track speed and then decelerate fast to stop at the station. As the distance between two consecutive stations is around one km, so slow start or slow braking is not affordable. For this purpose, metro uses two systems: 1. Distributive traction 6 2180V POWER OF TRACTION MOTOR 1536 hp 1156 hp 1156 hp TRACTIVE EFFORT 258 kN 322.6 KN 458kN BRAKING EFFORT 160kN 182 KN 260 kN TOTAL HP 5440 hp 6120 hp 6120 hp MAX SPEED 160 km/hr 130 km/hr 100 km/hr In earlier locos (WAP 5/ WAP 7/ WAG 9), traction motors driving the axles were DC motors. DC motors were initially used as they provide far superior speed and torque control In this locomotive units are installed under the bogies of the train. Either each or every other bogie has its propulsion unit. Generally, 4 wheels of the coach are powered and 4 are unpowered, therefore the complete train is started with all the propulsion units working in unity. Thus provide high starting torque, high acceleration and high braking capacity [6, 7]. This system can be used to achieve high speed also; in fact, most of the high speed trains around the world uses distributive traction (other than maglev). 2. Electrical Multiple Units (EMU) In India, metros work on this system. Here multiple units are connected in a single metro train. Usually every metro train consists of 3-4 EMU’s for obtaining high torque for the propulsion of the locomotive . Disadvantages in operation as conventional trains: 1. A fleet of MU cars cost more than conventional locomotive to maintain . 2. 3. 4. Have more parts means more maintenance and inspection. Bigger maintenance sheds required plus time consumption would be more as compared to single locomotive. They are not that effective on long routes. With an increase in demand of high speed mass transit of a nation, Talgo hybrid train has arrived as an ideal solution. It can run on both electrified and non-electrified lines, and within electrified lines both AC and DC supply is supported. Moreover propulsion bogies have been designed to allow dynamic gauge change. III. The new traction chain is adapted in two ways; one side considers the traction locomotives to be able to operate in diesel or electric mode, which also possesses the ability to detect and translate DC and AC supply during a change in supply system [8-10]. On the other side, the innovation in bogie design with adapted motors and gear boxes allows dynamic gauge change of the train [9,10]. This enables Talgo trains to adapt every situation with its advanced integrated system and fulfill the measures of safety and reliability. ADVANCED TRANSPORTATION SYSTEMS A. Pendolino Trains The word ‘Pendolino’ is derived from pendulum. It is an Italian family of trains which runs in Italy, Spain, Portugal, Russian federation, and U.K. . The high speed travel through Pendolino is still under research stage in Indian Railway industry. It has to go through a compatibility check on Indian railway tracks, after which, It may proceed for test runs. A geometric design of Pendolino is shown in Fig. 3. These trains are already being tested in the Spanish railway network, with a highly successful result, and will be shortly placed in commercial service, proving that the model is exportable to any part of the world, including India. A model of train imported for India Railways  is shown in Fig. 4. Fig. 3 Pendolino transit system  In these trains, a secondary suspension is provided between the bogie and the passenger car with the help of electromechanical actuators. Accelerometers are placed on each coach, which senses the lateral acceleration and provides the input to processing unit. These high speed controllers gives command to actuators resulting in tilting of the vehicle in the direction of curvature of the track [8,9]. The effect of lateral acceleration is not completely cancelled, as it may create nausea or motion sickness to the passengers sitting inside the train. This effect occurs because of the different inputs from eyes and body, where at one end the eye informs the brain that train is tilting on a curvature track, but on the other end the body informs that nothing is happening, therefore the passengers may not be able to cope up with this dual response, and hence produces a sense of motion. Due to this, only 70-80% effect is cancelled out . B. Talgo Trains Talgo Hybrid Train is a Spanish construction. It is an alltrack train built up with an aim of providing maximum interoperability, eliminating the limitations of the conventional railway system, such as variation in gauge, supply feeds and speed constraints on the curvature. Since a single train is capable enough to operate on almost any condition, it is accepted by many countries as a convenient means of transportation . Fig. 4 Talgo transit system  C. Magnetic Levitation Technology It is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational acceleration and any other acceleration . With maglev, a vehicle travels along a guide way using magnets to create both levitation and propulsion, which is shown below in Fig. 5. Propulsion Track N S N S Car-4Car-3 S Train N N Car-2Car-1 Train N S N Track S Train N S S S N S S NN N S Track Propulsion Levitation Guidance Fig. 5 Principles of Maglev technology  Combination of systems required for successful levitation and control of all 6 axes (3 translational, 3 rotational) in such a way that it provides at least one stable axis for the system to levitate and stabilize other axes . The various methods used for stable magnetic levitation are as follows- Servomechanism An on-off mechanism is used in electromagnets for producing the levitation . The electromagnet attracts the magnetic surface laid on the ground. When the electromagnet is switched on, the energization of current in the coils pulls it towards the magnetic surface. As soon as, the electromagnet is switched off, the mutual field coupling breaks and the distance between them becomes less than 10 cm. This gap is maintained using servo mechanism. Induced currents Induced current is another method to produce levitation. The principle behind the production of induced currents is Repulsion due to Lenz’s law. It can be achieved by relative motion (magnet dropped in copper tube), or by oscillating electromagnetic fields . Diamagnetic levitation It uses the property of diamagnetism i.e. object create a magnetic field opposite to an externally applied magnetic field. Mechanical constraint is used in levitation stability. If a magnetic surface is repelling other magnet, characterizing same polarities, it will try to get attached, but some constraint is provided in terms of displacement for maintaining the gap. Superconductors They are considered as perfect diamagnets, but require low temperature for operation. It uses a series of superconducting coils for the production of levitation force between the coils and the magnetic surface. A heavy cryogenic support is required to generate the force of levitation [11-13]. The block diagram of the maglev system enabling levitation, propulsion and guidance is shown in Fig.6. V. FACTORS AGAINST MAGLEV (INCLUDING ITS COMPATIBILITY TO INDIAN ECONOMY) [12,13] 1. High initial constructional cost makes it a costlier system to be adopted by a developing country. 2. Use of rare earth magnets, which have stronger magnetic field than ordinary ferrite or alnico, increasing its construction costs. 3. In view of the fact that presently in Indian railways, 7080% revenue from passengers comes from sleeper and general class, there doesn’t seems a promising future of maglev. 4. Present infrastructure does not even support complete use of durantos or rajdhanis on all sections. Thus we have to build separate corridor which demands huge infrastructure. 5. These systems need high maintenance and high precision in operation. VI. TYPES OF MAGLEV SYSTEMS There are two existing technologies of Maglev trains, Electro-Magnetic Suspension (EMS) and Electro-Dynamic Suspension (EDS), which use servo-controlled electromagnets and cryogenically cooled superconducting magnets, respectively [11-15]. EMS and EDS technologies are used in German Trans Rapid and Japanese Yamanashi trains respectively, operating at speeds of about 500 km/hr . They are described as followsA. Electromagnetic Suspension (EMS) Shanghai Maglev works on the principle of EMS . In EMS, the current to electromagnets is continually altered to change the strength of the magnetic field and allows a stable levitation to occur. It uses the property of attraction of opposite poles of magnet. In this system train is lifted from beneath the track. There are iron core electromagnets in carriages and ferromagnetic rails underside of the guideways. Propulsion is done with the help of linear synchronous motor . Fig. 6 Block diagram of conventional maglev system IV. ADVANTAGES OF MAGLEV OVER CONVENTIONAL TRAINS [11-14] 1. Significant reduction in wear and tear of the rolling stock. 2. Reduced size of the locomotive as well as linear motors. 3. Little or no pollution, less noisy. So, they are very suitable for urban as well as sub urban areas. 4. Ability to move the goods-wagons and the passenger coaches at a comparative higher speed, resulting into multifold increase of the system’s carrying capacity. 5. Increases the stability and allows higher permissible speeds because of the virtual gauge width over the complete surface of the coaches. 6. Smooth and comfortable rides, with a reduction of bumping on the seats of the passengers. Pros: Longer lifetime, lower operating costs, faster operation, low magnetic exposure. Cons: Expensive computer systems for monitoring magnetic strength. B. Electrodynamic Suspension (EDS) Japanese Maglev system follows the principle of Magnetic Repulsion for establishing the Electrodynamic mechanism . Japan is working on the concept of Maglev transportation since 1962. HSST Linimo (Linear motor maglev) and SC (Superconducting) Maglev are based on principle of magnetic repulsion between the track and the cars [12-14]. This system uses an electro dynamic suspension (EDS) mechanism. Superconducting magnets are installed in the train’s bogies which repels the coils on the guide way. It runs on rubber wheels initially up to 100-150 km/h speed. Below this speed, the induced current developed is not sufficient to lift the train. When the vehicle attains a certain speed, an electrical potential is developed between the superconducting magnets and the coils, and the current flows in such a way that it opposes the effect producing it (Lenz’s law), tries to centre the magnetic field and lift the train . Pros: Longer lifetime, lower operating costs, faster and reliable operation, safer during power outage. Cons: Significant incremental cost for additional cryogenic support required for cooling superconductive magnets. VII. LINEAR MOTORS Linear motors are the extended form of conventional rotary motors as shown in Fig. 7. Rotary motors produce torque circularly in rotor whereas linear motors give force linearly in translator. Depending on the usage, linear motors are categorized into high acceleration motors and low acceleration motors. High acceleration motors are used in the field of spacecraft propulsion, weapon firing, and hypervelocity collisions whereas, Low acceleration motors are used in the area of Maglev trains and ground based transportation applications [16, 17]. VIII. Permanent Magnets are emerging as a promising material in the production of high field strength for the development of High Speed Transit System. Linear motors is emerging for many applications such as rapid transit systems, amusement rides, automatic closing doors, lift applications, aircraft launching etc. With the advent of better power controllers and favorable cost, it is finding huge response in automation industries as well as in high speed transit applications. These can be used to reduce the cost of the system and to make the system compact, highly reliable and maintenance free. REFERENCES     Fig. 7 Conversion from conventional motor to linear motor  Depending on the working principle, linear motors are classified into four types which are Linear Induction Motors [LIM], Linear Synchronous Motors [LSM], Linear DC Motors and Linear Switched Reluctance Motors. Due to high cost and large heat loss, dc linear motors are not preferred in practical applications. LIM, LSM, LSRM are used in various applications like Maglev transit systems, automatic doors, lift applications, aircraft launching etc.. A linear version of Reluctance Motor is shown in Fig, 8           Fig. 8 Linear Reluctance motor for maglev application In recent years, linear switched reluctance motor has become an alternative to linear induction motor and linear synchronous motor. 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