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Power Systems Articles
Page 7 of 19
Electric Traction Motor: AC Series Motor
Many single phase AC motors have been developed for traction purposes but only compensated series type commutator motor is found to be best suited for traction services. Practically, the AC series motor is best suited for traction purpose because of high-starting torque.When DC series motor is fed from AC supply, it works but not satisfactorily due to the following reasons −If a DC series motor is fed from AC supply both the field and the armature currents reverse for every half cycle. Thus, unidirectional torque is developed in the motor at double frequency.When AC supply is given to the DC ...
Read MoreElectric Traction: Suitability of DC Series Motor in Traction
A DC series motor has the following characteristics that make it suitable for traction work −DC series motors develop high starting torque which is required for traction purpose.DC series motors produce high starting torque at low speeds and low torque at high speeds.The speed of a DC series motor can be controlled easily and effectively.The torque developed by a DC series motor is unaffected by variations in supply voltage.DC series motors are ideally suitable for parallel running. Because, the DC series motors when operated in parallel to drive a vehicle by means of different driving axles, share load almost equally ...
Read MoreElectric Traction: Buck and Boost Method of Speed Control of Traction Motors
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 MoreWhat are the auxiliary equipment used in an electric locomotive?
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 MoreElectric Traction: Calculation of Sag and Tension for Trolley Wire
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 MoreElectric Traction: Behn Eschenburg Scheme of Regenerative Braking
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 MoreWhat is Street Lighting? – Objective, Principle, Advantages & Disadvantages
A source of light that is mounted on a lamp column or pole either on the side of the road or within the median to provide illumination is known as street lighting.Street lighting is required along the road to have safer, comfortable, convenient and efficient movement of vehicles at night.Objective of Street LightingThe primary objectives of street lighting are −Street lighting is required to increase or enhance the community value of the street.Street lighting is provided along the road sides to make traffic and obstructions on the road clearly visible in order promote safety and convenience.Street lights also make the ...
Read MoreWhat is Flood Lighting? – Definition, Purpose, Calculation and Applications
The flooding of large surfaces with light through powerful projectors, where the light sources are concentrated into narrow light beams using specific reflectors is known as flood lighting. Flood lighting is an artificial light with high-intensity, broad beam.Purpose of Flood LightingThe flood lighting may be employed for the following purposes −To enhance the beauty of the ancient monuments at night.To illuminate the railway yards, car parking, sport stadiums, construction sites, etc.To illuminate the advertising boards and show-cases, etc.Location and Mounting of ProjectorsIn practice, there are two possible locations of projectors for flood lighting, which are −For small buildings, uniform flood ...
Read MoreWhat are Welding Defects? – Types, Causes, and Remedies
The irregularities formed in the given weld metal due to wrong welding process or incorrect welding patterns, etc. are known as welding defects.The following table elaborates the different types of welding defects, their causes, and how to prevent these defects −The irregularities formed in the given weld metal due to wrong welding process or incorrect welding patterns, etc. are known as welding defects.The following table elaborates the different types of welding defects, their causes, and how to prevent these defects −Welding DefectCauses of Welding DefectRemediesBlow holeToo fast cooling rate.Wet, unclear or damaged electrode.Too thick base metal.Long or short arc length.Rusted ...
Read MoreWhat is Photovoltaic or Solar Cell? – Construction, Working and Advantages
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 ...
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