Makarantar Tsafta Daji

Takaitaccen

Aikin da take yadda aiki na iya koyar da mutum ko abincin daga wurare zuwa wurare ne ake kiran electric traction drive. Daga cikin farkon alamomin aiki na electric drive, zan iya tabbatar da ce ya fiye da koyar da mutum da abinci. Traction drives suna kammala ne a biyu na tsohuwar - phase AC traction drive da DC traction drive.

Electric Traction Services

Electric traction services zai iya kammala ne haka:

• Electric trains

• Main - Line Trains

• Suburban Trains

• Electric buses, trams, and trolleys

• Battery and solar - powered vehicles

Zan bayyana wasu electric traction services na musamman a nan.

Electric Trains

Electric trains, wadanda suke rasa na rails masu nasara, suna kammala ne a main - line trains da suburban trains.

Main - Line Trains
A nan, kwakwalwa ta shirya motor a kan lokomotif ko kuma lokomotif na diesel da ke shirya energy da ita.

A lokomotif na electric, motor na koyar ta shirya a kan lokomotif. A kan rail way ta shirya overhead transmission line. Current collector, da ke shirya conductor strip, ta shirya a kan lokomotif. Wannan conductor strip ta ci gaba a kan supply conductor, don haka ya ba da electrical contact da power supply da lokomotif. Supply conductor ana kira contact wire. Don ba da inganci a kan current collector da supply wire, ana amfani da catenary cables da dropper wires.

A high - speed trains, ana amfani da pantograph collector. Wannan design mai kyau ta shahara ne da sunan pentagon. Collector na da conducting strip da ke shirya a kan contact wire tun daga baya da springs. Ana samun wannan conducting strip a kan steel, wanda ya yi muhimmanci a kan ba da pressure mai tsawo a kan maza da contact wire. Wannan pressure mai tsawo ne ya danganta da vertical oscillations, tare da hakan ya ba da electrical connection mai tsawo da inganci a lokacin da high - speed train ya ci gaba da speed mai tsawo. Wannan connection mai tsawo ne ya danganta da uninterrupted power supply zuwa electrical systems na train, tare da hakan ya ba da smooth da efficient operation.

Single - phase power supply ta shirya a kan duk railway track. Electric current ta shiga lokomotif a kan collector. Ta zaɓi primary coil of a step - down transformer ta koyar ta shiga ground da ke shirya a kan power supply a kan wheels na lokomotif. Secondary coil of the power transformer ta shirya power zuwa power modulator, wanda ya koyar ta shirya traction motor. Kuma secondary output of the transformer ta shirya power zuwa auxiliary devices kamar cooling fans da air - conditioning systems.

Suburban Trains
Suburban trains, wadanda ake kira local trains, an sanya a koyar da distance mai tsawo. Wadanda suke ci gaba da stops masu tsawo a kan intervals masu tsawo. Don inganta acceleration da deceleration performance, suburban trains suna amfani da motorized coaches. Wannan configuration na iya yanka tsari na weight da ke shirya a kan driving wheels zuwa total train weight.

Har motorized coach ta shirya electric drive system da pantograph collector. Yanzu, ana amfani da motorized da non - motorized coaches a ratio of 1:2. Don high - power suburban trains, wannan ratio zai iya zama 1:1. Trains composed of motorized and trailer coaches are known as Electrical Multiple Unit (EMU) trains. Power supply mechanism for suburban trains is similar to that of main - line trains, with one notable exception: underground suburban trains.

Underground trains utilize a direct - current (DC) power supply system. This choice is primarily due to the fact that DC supply systems require less clearance between the power conductor and the train body. Moreover, DC systems simplify the design of the power modulator, reducing both its complexity and cost. Unlike above - ground trains, underground trains do not employ overhead transmission lines. Instead, power is supplied either through the running rails or from conductors installed on one side of the tunnel.

Electric Buses, Trams and Trolleys
These types of electric vehicles typically feature a single - motor - driven coach design. They draw power from low - voltage DC overhead lines installed alongside the road. Given the relatively low current requirements, the current collection mechanism often consists of a rod with a grooved wheel at its end, or two rods connected by a contact bow. The collector system is engineered to be highly flexible, and it includes an additional conductor to facilitate the return of the electrical current, ensuring a stable and continuous power supply for the vehicle's operation.

Trams are a type of electric - powered vehicle that runs on rails and typically consists of a single - motor coach. In some cases, two or more unpowered trailer coaches are attached to increase passenger capacity. Their current collection system is comparable to that of electric buses. Notably, the return path for the electrical current can be established through one of the rails. As trams operate on fixed rails, their routes along the road are predetermined, providing a reliable and consistent transportation service.

Electric trolleys are primarily employed for the transportation of materials within mines and factories. These vehicles predominantly run on rails and share many similarities with trams, with the main difference lying in their physical shape.

Important Features of Electric Traction Drives

The key characteristics of electric traction drives are elaborated below

• High Torque Requirement: Traction drives need to generate substantial torque during the starting and acceleration phases to propel the heavy mass of the vehicle. This high - torque demand ensures that the train or other traction vehicle can overcome inertia and achieve the desired speed efficiently.

• Single - Phase AC Supply in AC Traction: For economic considerations, a single - phase power supply is commonly utilized in alternating - current (AC) traction systems. This choice helps in reducing costs related to infrastructure, power generation, and distribution, making the overall operation more financially viable.

• Voltage Fluctuations: The power supply in electric traction systems experiences significant voltage fluctuations. These fluctuations are particularly pronounced when the locomotive moves from one supply section to another, often resulting in momentary discontinuities. Such voltage variations can pose challenges to the stable operation of the traction equipment and require careful design and control strategies to mitigate their effects.

• Harmonic Interference: Both AC and DC traction systems inject harmonics into the power source. These harmonics can interfere with nearby telephone lines and signal systems, potentially causing disruptions to communication and signaling infrastructure. Adequate filtering and mitigation measures are essential to minimize this interference and ensure the proper functioning of these critical services.

• Braking Systems: Traction drives mainly rely on dynamic braking, which converts the kinetic energy of the moving vehicle into electrical energy, either dissipating it as heat or feeding it back into the power grid. Additionally, mechanical brakes are used when the vehicle is stationary to provide reliable stopping and holding capabilities, ensuring safety in all operating conditions.

Duty Cycle of Electric Traction Drives

The duty cycle of an electric traction drive can be effectively understood through the analysis of speed - time curves and power - torque - time diagrams. Consider a traction drive operating between two consecutive stations on a level track. At the start, the train accelerates using the maximum achievable torque. During this acceleration phase, the power consumption of the drive increases linearly with the rising speed, reflecting the energy required to overcome inertia and propel the vehicle forward.

At time t1, the traction drive reaches its base speed, and simultaneously, the maximum allowable power is attained. Following this, further acceleration proceeds under a constant - power condition. As the speed continues to increase during this phase, both the torque and the acceleration gradually decrease.

By time t2, the drive torque becomes equal to the load torque, at which point a steady speed is achieved. The acceleration process from 0 to t2 can be divided into two distinct stages. From 0 to t1, the acceleration is characterized by a constant torque, where the drive applies a consistent rotational force to rapidly build up speed. Then, from t1 to t2, the acceleration occurs under a constant - power regime. Here, as the speed rises, the drive sacrifices torque to maintain the fixed power output, resulting in a diminishing acceleration rate until the equilibrium with the load torque is established at t2.

Between time t2 and t3, the train maintains a constant speed while operating at a steady drive power. This period is referred to as the free - running phase. During this stage, the train glides smoothly along the track, with the driving force precisely balancing the resistive forces, ensuring a consistent and efficient motion.

When the appropriate moment arrives at time t4, the braking system is engaged. This action initiates a controlled deceleration process, gradually reducing the train's speed until it eventually comes to a halt at the next station, ready to serve the next batch of passengers or transport its cargo to the intended destination.