The circuit diagram of the buck and boost method of speed control of traction motors is shown in the figure.There are two traction motors viz. traction motor-I and traction motor-II. In this method of speed control, the armature of both the traction motors I and II and the motor-generator set are connected in series. This whole series combination is connected across the main supply.When the terminal voltage of the generator is equal to the supply voltage in magnitude but of opposite polarity and the main contactor (MC) is closed, the voltage across the traction motors will be zero and hence ... Read More

In addition to the main traction motors, the following additional equipment are required to be installed on an electric locomotive engine −Motor-Generator SetBatteryPantograph Operating EquipmentAir CompressorTraction Motor BlowersHeating EquipmentLet's check the functions of each of these equipment in detail.Motor–Generator SetThe motor-generator set used in the electric locomotives is of the two bearing type and it consists of a series motor and a shunt generator. The speed of the series motor at light load is limited by the ventilating fan and the voltage of the generator is controlled by an automatic voltage regulator (AVR).The generated voltage by the motor-generator set is ... Read More

An overhead wire of large cross-section made of copper or a copper alloy and provides the current required for the trolleys of electric vehicle is known as trolley wire.When a flexible wire is suspended horizontally between two pole supports, it would assume the form of catenary. But in case of tramways, the sag in the trolley wire rarely exceeds 1% to 1.5% of the span length and thus the trolley wire may be considered to hang in the form of a parabola as shown in the figure below.Let, $$\mathrm{Span\: length\: of\: trolley\: wire\: (in \: meters)\, \mathrm{\: =\: }\, 2\mathit{l} ... Read More

The method of electric braking of traction motor in which the motor remains connected to the supply line and return the braking energy to the supply system is known as regenerative braking.Figure-1 shows the connection diagram of Behn Eschenburg scheme of regenerative braking. In this scheme, an auxiliary transformer is used to excite the field winding of the traction motor. The armature of the traction motor is connected to the main transformer through a tap changer.A choke coil or iron cored reactor (Reactor-I) is inserted in between the armature of the traction motor and the tap changer as shown in ... Read More

An electrical device which converts light energy into electrical energy through the photovoltaic effect is known as photovoltaic cell or PV cell or solar cell. A photovoltaic cell is basically a specially designed p-n junction diode.Construction and Working of Photovoltaic CellThe construction of a photovoltaic cell is shown in the following figure.A photovoltaic cell consists of a base metal plate and it is made of either steel or aluminum over which a metallic selenium layer is situated which is light sensitive and acts as the positive terminal.An electrically conducting layer of cadmium oxide is applied by sputtering over the selenium ... Read More

LED LampAn optoelectronic device which emits light based on the principle of electroluminescence is known as LED (Light Emitting Diode) lamp.Electroluminescence is the emission of light due to the interaction of an electric field with a suitable solid. It was noticed in 1962 that a forward biased gallium-arsenide junction was found to be an efficient emitter of radiation.In case of electroluminescent p-n junctions, when biased in the forward direction, some of the energy dissipated is converted into light and hence, these are also called as semi-conductor lamps.Construction of LED LampFor the construction of LED lamps, following semiconductor materials are used ... Read More

An electrochemical process that removes material from a metallic workpiece is known as electropolishing. It is also known as electrochemical polishing or electrolytic polishing.Electro-polishing uses a combination of rectified current and a blended chemical electrolyte bath to remove flaws from the surface of a metal part. Electropolishing is often described as the reverse of electro-plating.Process of ElectropolishingThe schematic arrangement for the electropolishing is shown in the figure.In electro-polishing, the metallic workpiece is immersed in a temperature controlled bath of electrolyte and serves as the anode as it is connected to the positive terminal of a DC power supply.The negative terminal ... Read More

What is Electrodeposition?An electrolytic process by which one metal is deposited over other metal or non-metal is known as electrodeposition.Electrodeposition is widely used for decorative, protective and functional purposes. The process of electrodeposition includes −Electroplating − It is the process of deposition of metal over any metallic or non-metallic surfaces for protecting the metals from corrosion.Electro metallization − It is a process by which a metal can be deposited on a conducting base for decorative or protective purposes.Electro typing − It is a process used to reproduce printing, set up typing and medals, etc.Electro forming − It is a process ... Read More

Electric TractionThe action of pulling something over a surface (especially a road or a track) is known as traction. The action of drawing of vehicles by electric power derived from overhead wires, third rail, storage batteries or diesel generators mounted on the vehicles is known as electric traction. In simple words, the traction system which uses electric power for its operation is known as electric traction.The electric traction system is widely used in electric trains, tramcars, trolley buses and hybrid vehicles, etc.Advantages of Electric TractionThe major advantages of electric traction system over other types of traction (such as steam traction) ... Read More

The combination of an electric motor, energy transmitting shaft and control devices for motion control is known as electric drive. The following figure shows the block diagram of a typical electric drive.Based on their assembly, electric drives can be of the following three types −Individual DriveGroup DriveMulti-motor driveIn this article, let's check the advantages and disadvantages of using an Individual Electric Drive.What is an Individual Electric Drive?When an individual machine is fitted with its own electric motor, then the electric drive is known as individual electric drive. In case of individual electric drive, each operator has complete control on his ... Read More