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Utilisation of Electrical Power Articles
Page 5 of 12
Electric Traction: Trapezoidal Speed Time Curve
The speed-time curve of a main line service is best and most easily replaced by trapezoid. The figure shows the simplified trapezoidal speed-time curve for the main line service.Let, $\mathit{V_{m}}$ = Crest speed in kmph$\alpha$ = Acceleration in kmphps$\beta$ = Retardation in kmphpsT = Total time of run in seconds$\mathit{t_{\mathrm{1}}}$ = Acceleration time in seconds$\mathit{t_{\mathrm{2}}}$ = Free running time in seconds$\mathit{t_{\mathrm{3}}}$ = Retardation time in secondsD = Total distance of run in kmTherefore, the time of acceleration in seconds is given by, $$\mathrm{\mathit{t_{\mathrm{1}}}\:=\:\frac{\mathit{V_{m}}}{\alpha }}$$And the time for retardation in seconds is, $$\mathrm{\mathit{t_{\mathrm{3}}}\:=\:\frac{\mathit{V_{m}}}{\beta }}$$Hence, the time for free running in seconds is, ...
Read MoreElectric Traction: Quadrilateral Speed Time Curve
For urban and suburban services, the simplified quadrilateral speed-time curve of electric traction is shown in the figure.Let, $\alpha$ = Acceleration in kmphps$\beta$ = Braking retardation in kmphps$\beta_{c}$ = Coasting retardation in kmphpsV1 = Maximum speed at the end of acceleration in kmphV2 = Speed at the end of coasting in kmphT = Total time of run in secondst1 = Acceleration time in secondst2 = Coasting time in secondst3 = Braking time in secondsD = Total distance travell in kmTherefore, the time of acceleration is given by, $$\mathrm{\mathit{t_{\mathrm{1}}}\:=\:\frac{\mathit{V_{\mathrm{1}}}}{\alpha } }$$The time of coasting is given by, $$\mathrm{\mathit{t_{\mathrm{2}}}\:=\:\frac{\mathit{V_{\mathrm{1}}}-\mathit{V_{\mathrm{2}}}}{\beta_{c} } \:\:\:\cdot \cdot ...
Read MoreCrest Speed, Average Speed & Schedule Speed of an Electric Train
Crest Speed of Electric TrainThe maximum speed attained by an electric train during running is termed as its "crest speed". It is denoted by Vm.Average Speed of Electric TrainAverage speed is defined as the mean of the speeds attained by the electric train from start to stop. In other words, average speed is defined as the ratio of the distance covered by the train between two stops to the actual time of run. The average speed of train is denoted by Va and is given by, $$\mathrm{\mathrm{Average\: speed, }V_{a}\:=\:\frac{\mathrm{Distance\: between \:two\: stops\: (\mathit{D})}}{\mathrm{Actual\: time\: of\: run (\mathit{T_{\mathrm{run}}})}}\:\mathrm{kmph}}$$Schedule Speed of Electric ...
Read MoreGeneral Features of Traction Motors: Mechanical Features & Electrical Features
An electric motor which is used to provide the primary rotational torque to a machine such as electric locomotives, elevators, conveyors, trolley buses and other electric vehicles etc. is described as a traction motor.General Features of Traction MotorsThe general features of the electric motors used for traction purpose are classified into two classes as −Mechanical FeaturesElectrical FeaturesMechanical Features of Traction MotorsThe mechanical features of electric motors used for traction applications are listed below −Robustness - A traction motor must be mechanically strong and robust so that it can be capable of withstanding severe mechanical vibrations.Small Size - The overall dimensions ...
Read MoreSystems of Track Electrification: Composite System of Track Electrification
There is no system of track electrification which is good in all aspects, i.e. it suffers from some disadvantage.The composite system (as the name implies) combines together any two of the systems of track electrification so as to incorporate good points of both the systems. The composite systems presently being used are as −Single-Phase AC to Three-Phase AC SystemSingle-Phase AC to DC SystemSingle-Phase AC to Three-Phase AC SystemThe single-phase to three-phase system of track electrification is also known as Kando System. As the three phase AC traction system has some disadvantages such as tapping of power supply through two overhead conductors ...
Read MoreWhat is Third Rail Traction System? – Advantages and Disadvantages
What is Third Rail Traction System?A third rail is a method of providing electric power to an electric train through a semi-continuous rigid conductor placed along-side or between the running rails of a railway track.The third rail system uses an additional rail, called as conductor rail for supplying electrical power to the train. On most of the traction system, the conductor rail is placed on the sleeper ends outside the running rails, but in some cases a central conductor rail is used. The conductor rail is supported on ceramic insulators or insulated brackets, typically at intervals of 3 meters.The third ...
Read MoreWhat is Non-Electric Traction System? – Types, Advantages and Disadvantages
A non-electric traction system is a type of traction system that does not use electrical energy for the movement of a vehicle at any stage.Types of Non-Electric Traction SystemThe most popular non-electric traction systems are −Steam Engine DriveInternal Combustion (IC) Engine Drive or Diesel Engine DriveIn this article, we will highlight the advantages and disadvantages of using these two types of non-electric traction system.Steam Engine DriveIn the steam engine drives, the reciprocating steam engine is used for getting the required motive power. The steam engine drive is not used in these days due to various reasons. However, it is still ...
Read MoreWhat is Electro-Extraction? – Definition, Process and Applications
What is Electro-Extraction?Electro-extraction, also known as electro-winning can be defined in several ways as −Electro-extraction is an electrochemical process that is used for production of metals with commercially acceptable purity.Electro-extraction is the electro-deposition of metals from their ores that have been in electrolytic solution.Electro-extraction is the electrolytic process by which metals can be extracted or separated from their ores.Based upon the physical status of the metal ore, the metal can be extracted in following two ways −When the ore is in solid state - The ore is treated with strong acid to obtain its salt, again this salt is to ...
Read MoreAdvantages of 25 kV AC System of Track Electrification over DC System
DC Track Electrification SystemThe DC track electrification system is the one which uses 600 V DC to 750 V DC for urban railway services and 1500 V DC to 3000 V DC for main line services. In this DC system, the current collection system may be of the third rail type or overhead conductor type. In this system, the substation consists of a transformer and a mercury arc rectifier.25 kV AC SystemThis system of track electrification uses 25 kV industrial frequency AC supply collected from the overhead conductor and stepped down by a transformer in the locomotive. This reduced voltage ...
Read MoreSystems of Track Electrification: DC Electrification System
In the direct current (DC) system, DC series motors are used for running the electric trains. The DC series motors are used in electric trains due to their following advantages −They have very high starting torque.DC series motor has smaller weight to power ratio.DC series motor has self-speed regulating property.They have low maintenance cost.The DC series motor has high acceleration and retardation.DC Electrification SystemIn the DC system of track electrification, the DC power to be fed to the DC series motor is obtained from substations which are located at a distance of 3 to 5 km for urban and suburban ...
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