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What is a primary feature that a traction motor must possess to handle frequent starting and stopping?
Which mechanical feature is essential for a traction motor to ensure it can handle severe vibrations?
Why is high starting torque important for traction motors?
What is a significant electrical feature of traction motors that contributes to energy efficiency?
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What is the primary characteristic of an Electric Traction System?
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Which characteristic helps traction motors share load when operating in parallel?
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What is a factor that facilitates ease of maintenance in conductor-rail systems?
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Which of the following is categorized as a Non Electrical Traction system?
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What type of motor is commonly used in a DC traction system for its high starting torque?
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What material is primarily used for overhead contact wires to ensure durability?
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What minimizes the weight of traction motors and improves load-carrying capability?
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In which voltage range does a typical DC traction system operate?
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Where is the current collector shoe typically located in a traction motor system?
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What frequency range is typically used in a Single Phase AC Traction System?
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What is the function of rotary converters in a DC traction system?
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Which design feature of traction motors helps them to avoid dirt and dust interference?
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Which system is preferred for suburban services where there are frequent stops?
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What is the typical voltage range supplied to the overhead distribution wire in a Single Phase AC Traction System?
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Which type of traction system does NOT use electrical power to drive locomotives?
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What is the purpose of using a step-down transformer in an AC traction system?
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What is the preferred traction system for mainline and suburban services?
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In a three-phase traction system, what voltage are the three-phase induction motors typically operated at?
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Which quadrant describes the operation of a motor when it acts as a generator during the hoisting of an unloaded cage?
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What happens to the speed of a DC series motor when it is connected in series with another similar motor?
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What is the primary control method combined with the series-parallel method in electric traction?
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In which quadrant does a motor operate when moving a loaded cage downward using the weight of the load itself?
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Which characteristic is NOT true regarding a three-phase traction system?
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What is the primary advantage of a composite traction system?
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Which operation occurs in the third quadrant involving a downward motion of an empty cage?
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During the initial start-up of a DC series motor connected in series, what is the effect of using a starting rheostat?
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What is the primary function of the springs in the trolley bus setup?
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Which material is commonly used for the actual contact strip in a trolley bus?
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At what operating speed does the pantograph typically function in railways?
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Which of these is NOT a method for raising or lowering the pantograph?
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What is the purpose of maintaining continuous contact with the overhead wire for pantographs?
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What characteristic must a pantograph possess regarding changes in wire height?
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Which factor is crucial in the design to protect the pantograph during overhead system failures?
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What distinguishes a bow collector from a traditional trolley wire setup?
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What is the typical pressure range applied by pantographs?
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How does the design of the contact shoes typically differ in pantographs?
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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.
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Electrical Traction uses electrical power. The main types include:
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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.
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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.
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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.
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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.
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DC Traction: DC series motors are commonly used due to their high starting torque.
Speed-Torque Characteristics of Traction Motors
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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
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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
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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.
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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
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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.
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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.
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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.
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Current Collectors for Overhead Contact Wire:
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Trolley Collector: Used for trams and trolley buses.
- Consists of a grooved wheel on a pole that follows the trolley wire.
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Bow Collector: Used for railways.
- Consists of a flexible metal bow that follows the overhead wire.
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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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Trolley Collector: Used for trams and trolley buses.
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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.
