Found 52 Articles for Electric Traction

Electric Traction: Buck and Boost Method of Speed Control of Traction Motors

Manish Kumar Saini
Updated on 19-May-2022 12:12:36
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

What are the auxiliary equipment used in an electric locomotive?

Manish Kumar Saini
Updated on 19-May-2022 12:09:41
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

Electric Traction: Calculation of Sag and Tension for Trolley Wire

Manish Kumar Saini
Updated on 19-May-2022 12:04:54
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

Electric Traction: Behn Eschenburg Scheme of Regenerative Braking

Manish Kumar Saini
Updated on 19-May-2022 11:59:20
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

Mechanics of Train Movement and Derivation for Tractive Effort

Manish Kumar Saini
Updated on 03-May-2022 08:27:28
Mechanism of Train MovementThe essential mechanism of an electric locomotive is shown in the figure below.Here, the armature of the driving motor has a pinion of the diameter d1 attached to it. The tractive effort at the edge of the pinion is transferred to the driving wheel by means of a gearwheel.Let, T = Torque exterted by the motor in NmF1 = Tractive effort at the pinionFt = Tractive effort at the wheel$\gamma $ = Gear ratiod1 = Diameter of piniond2 = Diameter of gear wheelD = Diameter of driving wheel$\eta $ = Efficiency of power transmission from motor to ... Read More

Systems of Track Electrification: AC Electrification System

Manish Kumar Saini
Updated on 03-May-2022 08:24:50
There are two types of AC system of track electrification −Single-Phase Low-Frequency AC System (15 kV to 25 kV at 16$\frac{2}{3}$ Hz, 25 Hz and 50 Hz)Three-Phase AC System (3.3 kV to 3.6 kV at 16$\frac{2}{3}$ Hz)Single-Phase Low-Frequency AC SystemIn a single-phase low-frequency system of track electrification, an AC voltage of 15 kV at a frequency of 16$\frac{2}{3}$ to 25 Hz is used.The use of high voltage AC in the system reduces the current flowing through the overhead transmission line resulting in the reduced voltage drops and it helps in installing the substations at larger distances, about 50 to 80 ... Read More

Electric Traction: Trapezoidal Speed Time Curve

Manish Kumar Saini
Updated on 03-May-2022 08:19:33
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 More

Electric Traction: Quadrilateral Speed Time Curve

Manish Kumar Saini
Updated on 03-May-2022 08:16:12
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 More

Crest Speed, Average Speed & Schedule Speed of an Electric Train

Manish Kumar Saini
Updated on 03-May-2022 08:12:02
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 More

General Features of Traction Motors: Mechanical Features & Electrical Features

Manish Kumar Saini
Updated on 28-Apr-2022 08:43:11
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 More