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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 More
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 ... Read More
A negative booster is a separately excited DC generator whose armature is connected with negative bus-bar at the far end of the track through negative feeder. The connection diagram of the negative booster is shown in the figure below.As in case of DC traction system, the return current flows through the rails to the substations. Because of this current flow through the rails, some voltage drop exists along the track. Due to potential difference along the track, some of the return currents leak out to the earth and follow the path of low resistance provided by water pipes, gas pipes, ... Read More
Schedule Speed of an Electric TrainThe schedule speed of an electric train is defined as the ratio of the distance covered between two stops to the actual time of the run including the time for stop. The schedule speed is denoted by VS and is given by, $$\mathrm{\mathrm{Schedule\: speed}, \mathit{V_{\mathit{S}}}\:=\:\frac{\mathrm{Distance \:between\: two\: stops(\mathit{D})}}{Actual\: run\: time(\mathit{T_{\mathrm{run}}})\:+\:Time \:for\: stop(\mathit{T_{\mathrm{stop}}})}\:\:\:\cdot \cdot \cdot \mathrm{\left ( \mathrm{1} \right )}}$$$$\mathrm{\therefore \mathrm{Schedule\: speed}, \mathit{V_{\mathit{S}}}\:=\:\frac{\mathrm{Distance \:between\: two\: stops(\mathit{D})}}{Schedule\: time (\mathit{T_{S}})}\:\:\:\cdot \cdot \cdot \mathrm{\left ( \mathrm{2} \right )}}$$Where, TS is the schedule time in hours.Factors Affecting the Schedule SpeedThe factors that affect the schedule speed of an electric train ... Read More
The part of an electric motor that protects the motor from the contaminants in the environment in which it is operating and persons being from touch is called the motor enclosure.The motor enclosures are necessary for the following reasons −It protects the motor against foreign body and severe conditions.It protects the inner parts of the motor.It protects the operating personal from live parts of the motor such as winding terminals, slip rings, brushes, etc.Types of Motor EnclosuresIndian Standards (IS) 4691 have described codes for different types of enclosures. The most common types of electric motor enclosures are given as follows ... Read More
Electric motor drives are the basic assemblies used for the transformation of electrical power into mechanical energy. In simple words, the term "electric motor drive" is used to denote drives driven by electric motors.Types of Motors Used for Electric DrivesFollowing are the different types of motors used for industrial electric drives −DC series motorDC shunt motorCumulative compound DC motorSlip ring induction motorSquirrel cage induction motorDouble squirrel cage induction motorThree phase synchronous motorSingle-phase synchronous motorSingle-phase AC series motorRepulsion motorCapacitor-start induction-run motorCapacitor-start capacitor-run motorNow let's check in detail the applications of each of these motors.DC Shunt MotorDC shunt motor has medium starting ... Read More
A few days ago, I happened to read a humorous infographic in one of the reputed newspapers. clearly, the beloved cartoonist of the newspaper was trying to take a dig at the extremely competitive world. The infographic read Time will pass. Will you? This brought some smiles on my face and soon, I found myself lost in a whirlpool of emotions where my mind profoundly pondered and wandered into the nitty-gritty of examinations.Let me express this modicum of truth – Students generally hesitate to confront the glare of examination results. Despite learning and understanding various new concepts, despite toiling and ... Read More
Block Diagram of an AC LocomotiveThe following figure shows the block diagram of an AC locomotive.AC Locomotive - Function of Each PartThe working and function of each part of an AC locomotive is described below −The AC power at 25 kV is taken from the overhead conductor wire (called as catenary) through a pantograph and this high voltage supply is fed to a step–down transformer (provided with on load tap changer) installed in the locomotive itself, which converts the high voltage AC supply to low voltage AC supply.This low voltage AC supply obtained from the transformer is then converted into ... Read More
In this digital world, most of the business enterprises nowadays are aware of the importance of online presence and they are able to see the benefits of branding in digital format. The first thing in their mind is to develop a web portal. However, few entrepreneurs may not be technically aware that, the landing page is one of the most important aspects to look for. It is better to be aware of these basics before entering the online world.The landing page is a distinct page built for the sole objective of conversion. It is designed, written and developed to meet ... Read More
“More than the act of testing, the act of designing tests is one of the best bug preventers known.” – Boris BeizerWell, designing and maintaining the testing activities involves a lot of attention and takes precious times of the team. The pain of organizing the test cases, test suits, then keeping the records of the test results phases after phases, tracking the bugs, and then maintaining those various reports and metrics, a quality assurance person can understand who actually performs all those activities. Also tracing the requirements against a particular test case is another painful task when needed.How about a ... Read More