Electric Traction Systems Overview
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Questions and Answers

What is a primary feature that a traction motor must possess to handle frequent starting and stopping?

  • Low starting current
  • High rotational speed
  • Can withstand high temperature (correct)
  • Ability to operate in high humidity
  • Which mechanical feature is essential for a traction motor to ensure it can handle severe vibrations?

  • High efficiency
  • Robustness (correct)
  • Small size
  • Low weight
  • Why is high starting torque important for traction motors?

  • To maintain consistent speed
  • To start the motor under load (correct)
  • To ensure smooth deceleration
  • To reduce energy consumption
  • What is a significant electrical feature of traction motors that contributes to energy efficiency?

    <p>Electric braking ability</p> Signup and view all the answers

    What is the primary characteristic of an Electric Traction System?

    <p>It uses electricity to provide power to locomotives.</p> Signup and view all the answers

    Which characteristic helps traction motors share load when operating in parallel?

    <p>Similar speed-torque characteristics</p> Signup and view all the answers

    What is a factor that facilitates ease of maintenance in conductor-rail systems?

    <p>Easily inspectable components</p> Signup and view all the answers

    Which of the following is categorized as a Non Electrical Traction system?

    <p>Diesel Engine</p> Signup and view all the answers

    What type of motor is commonly used in a DC traction system for its high starting torque?

    <p>DC series motors</p> Signup and view all the answers

    What material is primarily used for overhead contact wires to ensure durability?

    <p>Silicon bronze</p> Signup and view all the answers

    What minimizes the weight of traction motors and improves load-carrying capability?

    <p>Minimum weight</p> Signup and view all the answers

    In which voltage range does a typical DC traction system operate?

    <p>1500-3000V</p> Signup and view all the answers

    Where is the current collector shoe typically located in a traction motor system?

    <p>Underneath the train</p> Signup and view all the answers

    What frequency range is typically used in a Single Phase AC Traction System?

    <p>16 2/3 or 25Hz</p> Signup and view all the answers

    What is the function of rotary converters in a DC traction system?

    <p>To convert AC power into DC power</p> Signup and view all the answers

    Which design feature of traction motors helps them to avoid dirt and dust interference?

    <p>Enclosed construction</p> Signup and view all the answers

    Which system is preferred for suburban services where there are frequent stops?

    <p>DC Traction System</p> Signup and view all the answers

    What is the typical voltage range supplied to the overhead distribution wire in a Single Phase AC Traction System?

    <p>15kV to 25kV</p> Signup and view all the answers

    Which type of traction system does NOT use electrical power to drive locomotives?

    <p>Non Electrical Traction</p> Signup and view all the answers

    What is the purpose of using a step-down transformer in an AC traction system?

    <p>To reduce high voltage to a safer, usable voltage</p> Signup and view all the answers

    What is the preferred traction system for mainline and suburban services?

    <p>Single-phase AC traction system</p> Signup and view all the answers

    In a three-phase traction system, what voltage are the three-phase induction motors typically operated at?

    <p>3000 to 3600V</p> Signup and view all the answers

    Which quadrant describes the operation of a motor when it acts as a generator during the hoisting of an unloaded cage?

    <p>Second Quadrant</p> Signup and view all the answers

    What happens to the speed of a DC series motor when it is connected in series with another similar motor?

    <p>Speed is halved</p> Signup and view all the answers

    What is the primary control method combined with the series-parallel method in electric traction?

    <p>Resistance control</p> Signup and view all the answers

    In which quadrant does a motor operate when moving a loaded cage downward using the weight of the load itself?

    <p>Fourth Quadrant</p> Signup and view all the answers

    Which characteristic is NOT true regarding a three-phase traction system?

    <p>Operates at a frequency of 50 Hz</p> Signup and view all the answers

    What is the primary advantage of a composite traction system?

    <p>Combined benefits of DC and AC systems</p> Signup and view all the answers

    Which operation occurs in the third quadrant involving a downward motion of an empty cage?

    <p>Reverse motoring</p> Signup and view all the answers

    During the initial start-up of a DC series motor connected in series, what is the effect of using a starting rheostat?

    <p>Limits starting current</p> Signup and view all the answers

    What is the primary function of the springs in the trolley bus setup?

    <p>To maintain upward pressure on the pole and collector</p> Signup and view all the answers

    Which material is commonly used for the actual contact strip in a trolley bus?

    <p>Aluminium</p> Signup and view all the answers

    At what operating speed does the pantograph typically function in railways?

    <p>As high as 110 or 130 Km p.h.</p> Signup and view all the answers

    Which of these is NOT a method for raising or lowering the pantograph?

    <p>Hydraulic lifted, gravity lowered</p> Signup and view all the answers

    What is the purpose of maintaining continuous contact with the overhead wire for pantographs?

    <p>To ensure consistent electrical current supply</p> Signup and view all the answers

    What characteristic must a pantograph possess regarding changes in wire height?

    <p>It should be adaptable to changes in height.</p> Signup and view all the answers

    Which factor is crucial in the design to protect the pantograph during overhead system failures?

    <p>It needs to be pliable to avoid damage.</p> Signup and view all the answers

    What distinguishes a bow collector from a traditional trolley wire setup?

    <p>It collects current without the need for wires.</p> Signup and view all the answers

    What is the typical pressure range applied by pantographs?

    <p>5 to 15 Kg</p> Signup and view all the answers

    How does the design of the contact shoes typically differ in pantographs?

    <p>They can be either cambered or straight.</p> Signup and view all the answers

    Study Notes

    Electric Traction Systems

    • Electric Traction involves using electricity to power locomotives, trams, trolleys, etc.
    • Track Electrification refers to supplying electric power to locomotives via overhead lines running along the track.

    Types of Traction Systems

    • Non-Electrical Traction utilizes non-electrical power sources like steam engines or diesel engines.
    • Electrical Traction uses electrical power. The main types include:
      • DC Traction: DC series motors are commonly used due to their high starting torque.
        • Operating voltage ranges between 1500-3000V.
        • AC supply is stepped down and converted to DC power at substations.
        • Preferred for suburban services and road transport due to frequent stops.
      • Single-Phase AC Traction: AC power is supplied to the locomotive.
        • AC series motors are typically used with operating voltages of 300V-400V at 16 2/3 or 25Hz.
        • Substations transform and change the frequency of the AC supply.
        • Preferred for mainline and suburban services.
      • Three-Phase AC Traction: Uses three-phase induction motors operating at 3000 to 3600V with a frequency of 16 2/3 Hz.
        • Requires two overhead conductors and the track rail as the third conductor.
      • Composite Traction: Combines DC and AC systems for the advantages of both.
        • Single phase to three phase: AC power is converted to three-phase within the locomotive.
        • Single phase to DC: AC power is converted to DC within the locomotive.

    Speed-Torque Characteristics of Traction Motors

    • Quadrantal Diagram visualizes the four quadrants of motor operation.
      • Quadrant I (Forward Motoring): Motor torque and speed are in the same direction, providing forward motion.
      • Quadrant II (Generator or Braking): Motor acts as a generator, providing negative torque to slow down the load.
      • Quadrant III (Reverse Motoring): Motor torque and speed are in opposite directions, creating reverse motion.
      • Quadrant IV (Reverse Braking): Motor provides positive torque to slow down the load in reverse motion.

    Series-Parallel Control

    • Series-Parallel Control adjusts speed by connecting motors in series or parallel.
      • Series Connection: Reduces voltage to each motor, resulting in lower speed.
      • Parallel Connection: Full voltage is applied to each motor, increasing speed.
    • Combination with Resistance Control: This method combines series-parallel connection with resistance control to achieve a wider range of speeds.

    General Features of Traction Motors

    • Mechanical Features:
      • Robustness: Traction motors must withstand severe mechanical vibrations.
      • Small Size: Minimizing motor diameter and overall size to fit under the locomotive.
      • Completely Enclosed: Protection from dirt, dust, and other elements.
      • Minimum Weight: Reduces locomotive weight, increasing load capacity and efficiency.
      • High Efficiency: Reduces energy losses, improving overall efficiency.
    • Electrical Features:
      • High Starting Torque: Essential for accelerating heavy loads during starting.
      • Easy Speed Control: Enables frequent starting and stopping.
      • High Temperature Resistance: Handles high temperatures generated during frequent operation.
      • High Overload Capacity: Handles temporary overloads.
      • Parallel Operation: Allows multiple motors to share the load equally.
      • Electric Braking Ability: Improves energy efficiency by utilizing regenerative braking.
      • Voltage Fluctuation Resistance: Tolerates fluctuations in supply voltage.
      • Good Commutation: Prevents sparking at brushes and commutator segments.

    Accessories for Track Electrification

    • Overhead Contact Wire: Conducts electricity to the locomotive.
      • Typically made of hard drawn copper, Cadmium-Copper or silicon bronze.
      • High tensile strength and electrical resistance make silicon-bronze a common choice.
    • Conductor-Rail System: Used for lower voltage (600V) suburban services.
      • Cheaper, requires less maintenance, and provides better visibility of signals.
      • One or two rails conduct electricity, with the track rail often used for return.
    • Current Collecting Shoes: Transfer electricity from the conductor rail or contact wire to the train.
      • Made of steel, pressing against the rail with a force of about 15 kg.
    • Current Collectors for Overhead Contact Wire:
      • Trolley Collector: Used for trams and trolley buses.
        • Consists of a grooved wheel on a pole that follows the trolley wire.
      • Bow Collector: Used for railways.
        • Consists of a flexible metal bow that follows the overhead wire.
      • Pantograph: Used for high speed and high current railway applications.
        • Consists of a joined frame with one or two sliding shoes.

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    Description

    This quiz covers the fundamentals of electric traction systems, including track electrification and their main types. Explore the differences between non-electrical and electrical traction, and learn about DC and single-phase AC traction systems. Perfect for those studying transportation engineering or electric systems in transit.

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