Electric Traction – I | Electrical Engineering SSC JE (Technical) - Electrical Engineering (EE) PDF Download

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      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
 
 
  
 
  
 
  
 
  
 
  
 
  
 
  
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
 
 
  
 
  
 
  
 
  
 
  
 
  
 
  
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o In electric traction system, in addition to the mechanical braking, electrical braking 
can also be used that reduces the wear on the brake shoes, wheels, etc. 
o Electrically operated vehicles can withstand for overloads, as the system is capable 
of drawing more energy from the system. 
In addition to the above advantages, the electric traction system suffers from the 
following drawbacks: 
o Electric traction system involves high erection cost of power system. 
 
o Interference causes to the communication lines due to the overhead 
distribution networks. 
o The failure of power supply brings whole traction system to stand still. 
 
o In an electric traction system, the electrically operated vehicles have to move only on 
the electrified routes. 
o Additional equipment should be needed for the provision of regenerative braking, it 
will increase the overall cost of installation. 
 
REVIEW OF EXISTING ELECTRIC TRACTION SYSTEM IN INDIA 
 
In olden days, first traction system was introduced by Britain in 1890 (600-V DC track). 
 
Electrification system was employed for the first traction vehicle. This traction system was 
 
introduced in India in the year 1925 and the first traction system employed in India was from 
 
Bombay VT to Igatpuri and Pune, with 1,500- V DC supply. This DC supply can be obtained 
 
for traction from substations equipped with rotary converters. Development in the rectifiers 
 
leads to the replacement of rotary converters by mercury arc rectifiers. But nowadays further 
 
development in the technology of semiconductors, these mercury arc valves are replaced by 
 
solid-state semiconductors devices due to fast traction system was introduced on 3,000-V DC. 
 
Further development in research on traction system by French international railways was 
 
suggested that, based on relative merits and demerits, it is advantageous to prefer to AC rather 
 
than DC both financially and operationally. Thus, Indian railways was introduced on 52-kV, 
 
50-Hz single-phase AC system in 1957; this system of track electrification leads to the 
 
reduction of the cost of overhead, locomotive equipment, etc. Various systems employed for 
 
track electrification are shown in Table . 
 
Table Track electrification systems 
 
SYSTEM OF TRACTION 
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      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
 
 
  
 
  
 
  
 
  
 
  
 
  
 
  
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o In electric traction system, in addition to the mechanical braking, electrical braking 
can also be used that reduces the wear on the brake shoes, wheels, etc. 
o Electrically operated vehicles can withstand for overloads, as the system is capable 
of drawing more energy from the system. 
In addition to the above advantages, the electric traction system suffers from the 
following drawbacks: 
o Electric traction system involves high erection cost of power system. 
 
o Interference causes to the communication lines due to the overhead 
distribution networks. 
o The failure of power supply brings whole traction system to stand still. 
 
o In an electric traction system, the electrically operated vehicles have to move only on 
the electrified routes. 
o Additional equipment should be needed for the provision of regenerative braking, it 
will increase the overall cost of installation. 
 
REVIEW OF EXISTING ELECTRIC TRACTION SYSTEM IN INDIA 
 
In olden days, first traction system was introduced by Britain in 1890 (600-V DC track). 
 
Electrification system was employed for the first traction vehicle. This traction system was 
 
introduced in India in the year 1925 and the first traction system employed in India was from 
 
Bombay VT to Igatpuri and Pune, with 1,500- V DC supply. This DC supply can be obtained 
 
for traction from substations equipped with rotary converters. Development in the rectifiers 
 
leads to the replacement of rotary converters by mercury arc rectifiers. But nowadays further 
 
development in the technology of semiconductors, these mercury arc valves are replaced by 
 
solid-state semiconductors devices due to fast traction system was introduced on 3,000-V DC. 
 
Further development in research on traction system by French international railways was 
 
suggested that, based on relative merits and demerits, it is advantageous to prefer to AC rather 
 
than DC both financially and operationally. Thus, Indian railways was introduced on 52-kV, 
 
50-Hz single-phase AC system in 1957; this system of track electrification leads to the 
 
reduction of the cost of overhead, locomotive equipment, etc. Various systems employed for 
 
track electrification are shown in Table . 
 
Table Track electrification systems 
 
SYSTEM OF TRACTION 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
Traction system is normally classified into two types based on the type of energy given 
as input to drive the system and they are: 
 
1. Non-electric traction system 
 
Traction system develops the necessary propelling torque, which do not involve the use of 
electrical energy at any stage to drive the traction vehicle known as electric traction 
system. Ex: Direct steam engine drive and direct internal combustion engine drive. 
 
2. Electric traction system 
 
Traction system develops the necessary propelling torque, which involves the use of 
electrical energy at any stage to drive the traction vehicle, known as electric traction 
system. Based upon the type of sources used to feed electric supply for traction 
system, electric traction may be classified into two groups: 
1. Self-contained locomotives. 
 
2. Electric vehicle fed from the distribution networks. 
 
Self-contained locomotives 
 
In this type, the locomotives or vehicles themselves have a capability of generating 
electrical energy for traction purpose. Examples for such type of locomotives are: 
1. Steam electric drive 
 
In steam electric locomotives, the steam turbine is employed for driving a generator 
used to feed the electric motors. Such types of locomotives are not generally used for 
traction because of some mechanical difficulties and maintenance problems. 
2. Diesel electric trains 
 
A few locomotives employing diesel engine coupled to DC generator used to feed the 
electric motors producing necessary propelling torque. Diesel engine is a variable high-
speed type that feeds the self- or separately excited DC generator. The excitation for 
generator can be supplied from any auxiliary devices and battery. Generally, this type of 
traction system is suggested in the areas where coal and steam tractions are not available. 
The advantages and disadvantages of the diesel engine drive are given below: 
 
Advantages 
 
o As these are no overhead distribution system, initial cost 
is low. o Easy speed control is possible. 
o Power loss in speed control is very low 
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      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
 
 
  
 
  
 
  
 
  
 
  
 
  
 
  
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o In electric traction system, in addition to the mechanical braking, electrical braking 
can also be used that reduces the wear on the brake shoes, wheels, etc. 
o Electrically operated vehicles can withstand for overloads, as the system is capable 
of drawing more energy from the system. 
In addition to the above advantages, the electric traction system suffers from the 
following drawbacks: 
o Electric traction system involves high erection cost of power system. 
 
o Interference causes to the communication lines due to the overhead 
distribution networks. 
o The failure of power supply brings whole traction system to stand still. 
 
o In an electric traction system, the electrically operated vehicles have to move only on 
the electrified routes. 
o Additional equipment should be needed for the provision of regenerative braking, it 
will increase the overall cost of installation. 
 
REVIEW OF EXISTING ELECTRIC TRACTION SYSTEM IN INDIA 
 
In olden days, first traction system was introduced by Britain in 1890 (600-V DC track). 
 
Electrification system was employed for the first traction vehicle. This traction system was 
 
introduced in India in the year 1925 and the first traction system employed in India was from 
 
Bombay VT to Igatpuri and Pune, with 1,500- V DC supply. This DC supply can be obtained 
 
for traction from substations equipped with rotary converters. Development in the rectifiers 
 
leads to the replacement of rotary converters by mercury arc rectifiers. But nowadays further 
 
development in the technology of semiconductors, these mercury arc valves are replaced by 
 
solid-state semiconductors devices due to fast traction system was introduced on 3,000-V DC. 
 
Further development in research on traction system by French international railways was 
 
suggested that, based on relative merits and demerits, it is advantageous to prefer to AC rather 
 
than DC both financially and operationally. Thus, Indian railways was introduced on 52-kV, 
 
50-Hz single-phase AC system in 1957; this system of track electrification leads to the 
 
reduction of the cost of overhead, locomotive equipment, etc. Various systems employed for 
 
track electrification are shown in Table . 
 
Table Track electrification systems 
 
SYSTEM OF TRACTION 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
Traction system is normally classified into two types based on the type of energy given 
as input to drive the system and they are: 
 
1. Non-electric traction system 
 
Traction system develops the necessary propelling torque, which do not involve the use of 
electrical energy at any stage to drive the traction vehicle known as electric traction 
system. Ex: Direct steam engine drive and direct internal combustion engine drive. 
 
2. Electric traction system 
 
Traction system develops the necessary propelling torque, which involves the use of 
electrical energy at any stage to drive the traction vehicle, known as electric traction 
system. Based upon the type of sources used to feed electric supply for traction 
system, electric traction may be classified into two groups: 
1. Self-contained locomotives. 
 
2. Electric vehicle fed from the distribution networks. 
 
Self-contained locomotives 
 
In this type, the locomotives or vehicles themselves have a capability of generating 
electrical energy for traction purpose. Examples for such type of locomotives are: 
1. Steam electric drive 
 
In steam electric locomotives, the steam turbine is employed for driving a generator 
used to feed the electric motors. Such types of locomotives are not generally used for 
traction because of some mechanical difficulties and maintenance problems. 
2. Diesel electric trains 
 
A few locomotives employing diesel engine coupled to DC generator used to feed the 
electric motors producing necessary propelling torque. Diesel engine is a variable high-
speed type that feeds the self- or separately excited DC generator. The excitation for 
generator can be supplied from any auxiliary devices and battery. Generally, this type of 
traction system is suggested in the areas where coal and steam tractions are not available. 
The advantages and disadvantages of the diesel engine drive are given below: 
 
Advantages 
 
o As these are no overhead distribution system, initial cost 
is low. o Easy speed control is possible. 
o Power loss in speed control is very low 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o Time taken to bring the locomotive into service is less. 
 
o In this system, high acceleration and braking retardation can be obtained compared 
to steam locomotives. 
o The overall efficiency is high compared to steam locomotives. 
 
Disadvantages 
 
o The overloading capability of the diesel engine is less. 
 
o The running and maintenance costs are high. 
 
o The regenerative braking cannot be employed for the diesel engine drives. 
 
Petrol electric traction 
 
This system of traction is used in road vehicles such as heavy lorries and buses These 
vehicles are capable of handling overloads. At the same time, this system provides fine 
and smooth control so that they can run along roads without any jerking. Battery drives In 
this drive, the locomotive consists of batteries used to supply power to DC motors 
employed for driving the vehicle. This type of drives can be preferred for frequently 
operated services such as local delivery goods traction in industrial works and mines, etc. 
This is due to the unreliability of supply source to feed the electric motors. Electric vehicles 
fed from distribution network Vehicles in electrical traction system that receives power from 
over head distribution network fed or substations with suitable spacing. Based on the 
available supply, these groups of vehicles are further subdivided into: 
 
1. System operating with DC supply. Ex: tramways, trolley buses, and railways. 
 
2. System operating with AC supply. Ex: railways. 
 
Systems operating with DC supply 
 
In case if the available supply is DC, then the necessary propelling power can be obtained 
for the vehicles from DC system such as tram ways, trolley buses, and railways. 
 
Tramways: Tramways are similar to the ordinary buses and cars but only the difference is they are 
able to run only along the track. Operating power supply for the tramways is 500-V DC tramways 
are fed from single overhead conductor acts as positive polarity that is fed at suitable points from 
either power station or substations and the track rail acts as return conductor. The equipment used 
in tramways is similar to that used in railways but with small output not more than 40–50 kW. 
Usually, the tramways are provided with two driving axels to control the speed of the vehicles from 
either ends. The main drawback of tramways is they have to run along the 
Page 5


      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
 
 
  
 
  
 
  
 
  
 
  
 
  
 
  
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o In electric traction system, in addition to the mechanical braking, electrical braking 
can also be used that reduces the wear on the brake shoes, wheels, etc. 
o Electrically operated vehicles can withstand for overloads, as the system is capable 
of drawing more energy from the system. 
In addition to the above advantages, the electric traction system suffers from the 
following drawbacks: 
o Electric traction system involves high erection cost of power system. 
 
o Interference causes to the communication lines due to the overhead 
distribution networks. 
o The failure of power supply brings whole traction system to stand still. 
 
o In an electric traction system, the electrically operated vehicles have to move only on 
the electrified routes. 
o Additional equipment should be needed for the provision of regenerative braking, it 
will increase the overall cost of installation. 
 
REVIEW OF EXISTING ELECTRIC TRACTION SYSTEM IN INDIA 
 
In olden days, first traction system was introduced by Britain in 1890 (600-V DC track). 
 
Electrification system was employed for the first traction vehicle. This traction system was 
 
introduced in India in the year 1925 and the first traction system employed in India was from 
 
Bombay VT to Igatpuri and Pune, with 1,500- V DC supply. This DC supply can be obtained 
 
for traction from substations equipped with rotary converters. Development in the rectifiers 
 
leads to the replacement of rotary converters by mercury arc rectifiers. But nowadays further 
 
development in the technology of semiconductors, these mercury arc valves are replaced by 
 
solid-state semiconductors devices due to fast traction system was introduced on 3,000-V DC. 
 
Further development in research on traction system by French international railways was 
 
suggested that, based on relative merits and demerits, it is advantageous to prefer to AC rather 
 
than DC both financially and operationally. Thus, Indian railways was introduced on 52-kV, 
 
50-Hz single-phase AC system in 1957; this system of track electrification leads to the 
 
reduction of the cost of overhead, locomotive equipment, etc. Various systems employed for 
 
track electrification are shown in Table . 
 
Table Track electrification systems 
 
SYSTEM OF TRACTION 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
Traction system is normally classified into two types based on the type of energy given 
as input to drive the system and they are: 
 
1. Non-electric traction system 
 
Traction system develops the necessary propelling torque, which do not involve the use of 
electrical energy at any stage to drive the traction vehicle known as electric traction 
system. Ex: Direct steam engine drive and direct internal combustion engine drive. 
 
2. Electric traction system 
 
Traction system develops the necessary propelling torque, which involves the use of 
electrical energy at any stage to drive the traction vehicle, known as electric traction 
system. Based upon the type of sources used to feed electric supply for traction 
system, electric traction may be classified into two groups: 
1. Self-contained locomotives. 
 
2. Electric vehicle fed from the distribution networks. 
 
Self-contained locomotives 
 
In this type, the locomotives or vehicles themselves have a capability of generating 
electrical energy for traction purpose. Examples for such type of locomotives are: 
1. Steam electric drive 
 
In steam electric locomotives, the steam turbine is employed for driving a generator 
used to feed the electric motors. Such types of locomotives are not generally used for 
traction because of some mechanical difficulties and maintenance problems. 
2. Diesel electric trains 
 
A few locomotives employing diesel engine coupled to DC generator used to feed the 
electric motors producing necessary propelling torque. Diesel engine is a variable high-
speed type that feeds the self- or separately excited DC generator. The excitation for 
generator can be supplied from any auxiliary devices and battery. Generally, this type of 
traction system is suggested in the areas where coal and steam tractions are not available. 
The advantages and disadvantages of the diesel engine drive are given below: 
 
Advantages 
 
o As these are no overhead distribution system, initial cost 
is low. o Easy speed control is possible. 
o Power loss in speed control is very low 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
o Time taken to bring the locomotive into service is less. 
 
o In this system, high acceleration and braking retardation can be obtained compared 
to steam locomotives. 
o The overall efficiency is high compared to steam locomotives. 
 
Disadvantages 
 
o The overloading capability of the diesel engine is less. 
 
o The running and maintenance costs are high. 
 
o The regenerative braking cannot be employed for the diesel engine drives. 
 
Petrol electric traction 
 
This system of traction is used in road vehicles such as heavy lorries and buses These 
vehicles are capable of handling overloads. At the same time, this system provides fine 
and smooth control so that they can run along roads without any jerking. Battery drives In 
this drive, the locomotive consists of batteries used to supply power to DC motors 
employed for driving the vehicle. This type of drives can be preferred for frequently 
operated services such as local delivery goods traction in industrial works and mines, etc. 
This is due to the unreliability of supply source to feed the electric motors. Electric vehicles 
fed from distribution network Vehicles in electrical traction system that receives power from 
over head distribution network fed or substations with suitable spacing. Based on the 
available supply, these groups of vehicles are further subdivided into: 
 
1. System operating with DC supply. Ex: tramways, trolley buses, and railways. 
 
2. System operating with AC supply. Ex: railways. 
 
Systems operating with DC supply 
 
In case if the available supply is DC, then the necessary propelling power can be obtained 
for the vehicles from DC system such as tram ways, trolley buses, and railways. 
 
Tramways: Tramways are similar to the ordinary buses and cars but only the difference is they are 
able to run only along the track. Operating power supply for the tramways is 500-V DC tramways 
are fed from single overhead conductor acts as positive polarity that is fed at suitable points from 
either power station or substations and the track rail acts as return conductor. The equipment used 
in tramways is similar to that used in railways but with small output not more than 40–50 kW. 
Usually, the tramways are provided with two driving axels to control the speed of the vehicles from 
either ends. The main drawback of tramways is they have to run along the 
      Utilisation of Electrical Energy  
 
                                                                                                                                                                                                                                                                                        
 
guided routes only. Rehostatic and mechanical brakings can be applied to tramways. 
Mechanical brakes can be applied at low speeds for providing better saturation where 
electric braking is ineffective, during the normal service. The erection and maintenance 
costs of tramways are high since the cost of overhead distribution structure is costlier 
and sometimes, it may cause a source of danger to other road users. 
 
Trolley buses: The main drawback of tramways is, running along the track is avoided in case of 
trolley buses. These are electrically operated vehicles, and are fed usually 600-V DC from two 
overhead conductors, by means of two collectors. Even though overhead distribution structure is 
costlier, the trolley buses are advantageous because, they eliminate the necessity of track in the 
roadways. In case of trolley buses, rehostatic braking is employed, due to high adhesion between 
roads and rubber types. A DC compound motor is employed in trolley buses. 
 
SYSTEM OF TRACK ELECTRIFICATION 
 
Now a day, based on the available supply, the track electrification system are categorized into. 
 
1. DC system. 
 
2. Single-phase AC system. 
 
3. Three-phase AC system. 
 
4. Composite system. 
 
1 DC system 
 
In this system of traction, the electric motors employed for getting necessary propelling 
torque should be selected in such a way that they should be able to operate on DC 
supply. Examples for such vehicles operating based on DC system are tramways and 
trolley buses. Usually, DC series motors are preferred for tramways and trolley buses 
even though DC compound motors are available where regenerative braking is 
desired. The operating voltages of vehicles for DC track 
electrification system are 600, 750, 1,500, and 3,000 V. Direct current at 600–750 V is universally 
employed for tramways in the urban areas and for many suburban and main line railways, 1,500–
3,000 V is used. In some cases, DC supply for traction motor can be obtained from substations 
equipped with rotary converters to convert AC power to DC. These substations receive AC power 
from 3-f high voltage line or single-phase overhead distribution network. The operating voltage for 
traction purpose can be justified by the spacing between stations and the type of traction motors 
available. Theses substations are usually automatic and