11. AC DC 3-Phase EMUs
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Questions and Answers

What role does the diverting chopper play during regenerative braking?

  • It converts AC to DC power.
  • It provides dynamic brakes. (correct)
  • It increases the train's speed.
  • It helps in accelerating the train.

    • What voltage does the down chopper convert from?

  • 2200 volts DC (correct)
  • 110 volts AC
  • 415 volts AC
  • 530 volts AC

    • What is the output of the 20 kVA inverter?

  • 530 volts DC
  • 140 volts AC
  • 3-phase 415 volts AC (correct)
  • 220 volts DC

    • Which of the following supplies power to lights and fans in the coaches?

    <p>Auxiliary Transformer</p> Signup and view all the answers

    What is the function of the 7 kW battery charger?

    <p>Charge batteries and feed control supply</p> Signup and view all the answers

    What voltage is supplied to auxiliary machines from the auxiliary transformer?

    <p>415 volts 3-phase AC</p> Signup and view all the answers

    What is the primary function of the Driver’s Control Switch (DCS)?

    <p>To switch the train on and enable functions</p> Signup and view all the answers

    How is the load of lights and fans distributed across the phases?

    <p>Distributed across a single phase of 140 volts</p> Signup and view all the answers

    How many secondary windings does the auxiliary transformer have?

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

    Which equipment is fed by the 50 kVA inverter?

    <p>Auxiliary Transformer</p> Signup and view all the answers

    What is the service speed specified in the given information?

    <p>2750 rpm</p> Signup and view all the answers

    Which reset is applicable for fault codes 12 and 13?

    <p>Auto reset</p> Signup and view all the answers

    If the traction temperature is too high, which fault message would be displayed?

    <p>Traction and Aux. Off - TFP temp. too high</p> Signup and view all the answers

    What does a fault code of 39 indicate?

    <p>Traction and Aux. Off - Pantograph control failing</p> Signup and view all the answers

    Which of the following fault codes requires a reset through a laptop?

    <p>86, temperature sensor for traction motor 1</p> Signup and view all the answers

    What is the primary function of the High Voltage Detection Device (HVDD)?

    <p>To detect line voltage and regulate HVCC and MVCC</p> Signup and view all the answers

    When the OHE supply is in AC mode, what voltage is fed to the medium voltage change over switch (MVCC) after step down?

    <p>1473 V AC</p> Signup and view all the answers

    What does the line converter primarily convert?

    <p>1473 V AC or 1500 V DC to stabilized 2200 V DC</p> Signup and view all the answers

    What happens when the DC link voltage exceeds a preset voltage?

    <p>The diverting chopper functions</p> Signup and view all the answers

    How many traction motors are fed by the 3-Phase Traction Inverter?

    <p>4</p> Signup and view all the answers

    Which device is responsible for protecting the power circuit from lightning?

    <p>Main Lightning Arrestor</p> Signup and view all the answers

    What type of motors are employed as traction motors in the system?

    <p>Three-phase Squirrel Cage Induction Motors</p> Signup and view all the answers

    What type of switch connects the pantograph to either the AC or DC circuit?

    <p>High Voltage Change Over Switch (HVCC)</p> Signup and view all the answers

    What components are involved in forming the DC line filter?

    <p>Inductor, Capacitor, and Resistor</p> Signup and view all the answers

    What is the primary advantage of using MOSFETs over bipolar transistors in low voltage applications?

    <p>Voltage-controlled operation</p> Signup and view all the answers

    What characterizes the Gate Turn Off (GTO) Thyristor?

    <p>It can be turned off by a negative gate current pulse</p> Signup and view all the answers

    What feature of the IGBT combines that of MOSFETs and BJTs?

    <p>Low on-state power loss</p> Signup and view all the answers

    What is the typical range of gate current needed to turn off a GTO Thyristor?

    <p>¼ to 1/5 of the main current</p> Signup and view all the answers

    Why is a snubbing circuit required in power electronic devices?

    <p>To protect against excessive di/dt and dv/dt</p> Signup and view all the answers

    What is a significant drawback of using Bipolar Transistors compared to MOSFETs?

    <p>Complexity of the triggering circuit</p> Signup and view all the answers

    What happens to the conduction of a GTO Thyristor when a negative bias is applied at the gate?

    <p>The base drive of both transistors is removed</p> Signup and view all the answers

    What is the purpose of the VCB / DCCB Trip switch?

    <p>To trip the circuit breaker</p> Signup and view all the answers

    Which of the following configurations must be selected for the dead-man switch to be activated?

    <p>Throttle handle must be turned for approximately 5 degrees</p> Signup and view all the answers

    What is the purpose of the coasting position (C) in the traction/brake controller?

    <p>To allow the train to move without further acceleration</p> Signup and view all the answers

    How many traction positions are available in the traction/brake controller?

    <p>7</p> Signup and view all the answers

    What does the mode selector do?

    <p>Designates the driving direction</p> Signup and view all the answers

    Which switch is NOT present in the first row of switches?

    <p>Lamp Test</p> Signup and view all the answers

    What type of switch is used to apply or release the parking brake?

    <p>Parking Brake ON / OFF switch</p> Signup and view all the answers

    Which of the following is a function of the Fault Indication Panel?

    <p>Indicating a general fault</p> Signup and view all the answers

    Which of the following positions is NOT part of the traction/brake controller?

    <p>Park position</p> Signup and view all the answers

    What is the maximum number of brake positions available in the traction/brake controller?

    <p>7</p> Signup and view all the answers

    Which fault code indicates that both Inductor vessel fans are failing?

    <p>11</p> Signup and view all the answers

    To which components do fault codes 86, 87, 88, and 89 correspond?

    <p>Temperature sensors</p> Signup and view all the answers

    What is indicated by the fault code 15?

    <p>TFP failure</p> Signup and view all the answers

    Which reset can be applied for fault codes 30 and 33?

    <p>Maintenance reset</p> Signup and view all the answers

    Which warning message corresponds to the failure of HT Room fans both speed?

    <p>22</p> Signup and view all the answers

    What is the primary feature that allows a GTO Thyristor to be turned off?

    <p>Application of a negative gate current pulse</p> Signup and view all the answers

    Which statement best describes the construction of an IGBT?

    <p>It combines the desirable features of a MOSFET and a bipolar transistor.</p> Signup and view all the answers

    What is the main disadvantage of using bipolar transistors compared to MOSFETs in low voltage applications?

    <p>They have higher base currents, making the circuit bulky.</p> Signup and view all the answers

    Why is a snubbing circuit necessary for power electronic devices?

    <p>To prevent damage from excessive di/dt and dv/dt.</p> Signup and view all the answers

    Which characteristic of GTOs allows for compactness and cost-effectiveness in inverter circuits?

    <p>The absence of forced commutation circuitry.</p> Signup and view all the answers

    What advantage does a MOSFET possess over a bipolar transistor concerning the triggering circuit?

    <p>It requires a lower input current.</p> Signup and view all the answers

    What is the role of the down chopper in the electrical system?

    <p>It converts 2200 volts DC to a lower voltage for various devices.</p> Signup and view all the answers

    What occurs to a GTO Thyristor's conduction state when a negative bias is applied to its gate?

    <p>Conduction ceases as base drive of the transistors is removed.</p> Signup and view all the answers

    Which component is responsible for converting 530 volts DC to 3-phase 415 volts AC for the main compressor motor?

    <p>20 kVA Inverter</p> Signup and view all the answers

    Which voltage is supplied to the auxiliary machines from the auxiliary transformer?

    <p>415 volts 3-phase AC</p> Signup and view all the answers

    What voltage does the 7 kW battery charger convert 530 volts DC to?

    <p>110 volts DC</p> Signup and view all the answers

    During which mode are dynamic brakes activated in the train system?

    <p>Regenerative braking mode</p> Signup and view all the answers

    What does the driver's control switch (DCS) primarily enable?

    <p>Switching on the train and enabling master controller functions</p> Signup and view all the answers

    What components are included in the driving cab of the AC DC BHEL EMU?

    <p>Driver’s panel and Driver's Control Switch</p> Signup and view all the answers

    How is the load of lights and fans distributed across the phases in the system?

    <p>On a single phase of 140 volts evenly</p> Signup and view all the answers

    Which function does the switch panel of the driving cab provide?

    <p>Allowing the driver to control multiple functions through switches</p> Signup and view all the answers

    What is the primary output voltage of the traction inverter?

    <p>1950 V AC</p> Signup and view all the answers

    Which relay is responsible for powering off the fans in the motor coach?

    <p>213 K 35</p> Signup and view all the answers

    What is the continuous power rating of the traction motor?

    <p>295 kW</p> Signup and view all the answers

    What is the primary voltage requirement for the line converter in DC mode?

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

    What is the maximum current rating for the traction converter regardless of the mode?

    <p>900 Amps</p> Signup and view all the answers

    Which relay is used for selecting 50% light ON in the motor coach?

    <p>213 K 24</p> Signup and view all the answers

    What is the turns ratio of the traction transformer?

    <p>17:1</p> Signup and view all the answers

    What is the cooling medium used in the Aux. Down chopper?

    <p>MIDEL Synthetic Ester</p> Signup and view all the answers

    What is the output voltage of the aux. down chopper?

    <p>530 V DC</p> Signup and view all the answers

    What is the voltage supplied to the motor coach for input from either side?

    <p>110 V</p> Signup and view all the answers

    What occurs when a brake controller is not in the running position?

    <p>The train cannot operate above 5 km/h.</p> Signup and view all the answers

    In the case of a MINOR FAULT, what is the expected performance outcome?

    <p>Performance may be reduced but traction power is still available.</p> Signup and view all the answers

    What light indicates a General Fault in the system?

    <p>General Fault light will illuminate upon switching ON DCS.</p> Signup and view all the answers

    What action should the driver take if a fault message is displayed?

    <p>Inform maintenance staff after service.</p> Signup and view all the answers

    Which position of the pneumatic brake controller is NOT a normal operating position?

    <p>Emergency position.</p> Signup and view all the answers

    What happens to the functionality of traction power and ED brake in case of an OFF traction fault?

    <p>Both traction power and ED brake are lost.</p> Signup and view all the answers

    Which screen is used to view fault messages in the Driver's Display Unit (DDU)?

    <p>F1 - Message presentation screen.</p> Signup and view all the answers

    What is the correct procedure to clear a fault via the FAULT RESET button?

    <p>Press the button for at least 1 second if the fault has disappeared.</p> Signup and view all the answers

    What information does the F4 screen display on the Driver's Display Unit?

    <p>Line voltage, line current, speed, and energy metrics.</p> Signup and view all the answers

    When does the General Fault light illuminate and when does it go off?

    <p>It illuminates upon DCS switch ON and goes off after 10 seconds.</p> Signup and view all the answers

    Study Notes

    11.AC DC 3-phase EMUs

    • Several technical improvements have been incorporated into EMU stocks, including air brake systems, improved traction motors, thyristor control, and improved lighting.
    • Despite these enhancements, DC series motors remain the primary drive system.
    • Commutators and brushes in DC motors limit reliability.
    • AC induction motors offer high starting torque and better speed control, making them suitable for use with variable voltage/variable frequency (VVVF) control.
    • 3-phase AC induction motors, with VVVF control, provide energy savings, reduced maintenance, and increased reliability.
    • These EMUs can be used for both AC and DC traction, which is beneficial in suburban areas like Mumbai where DC-AC conversion is required.

    Advantages of 3-Phase Drive with GTO Thyristors over Conventional Technology

    • Increased energy efficiency.
    • Smoother passenger experience due to stepless control.
    • Improved wheel-rail adhesion.
    • Advanced diagnostics and compact equipment design.
    • High power-to-weight ratio.
    • High voltage/low current operation.
    • Regenerative braking capability.
    • Unity power factor in AC traction.

    Special Features of 3-Phase AC-DC EMUs

    • GTO-based traction converters/inverters with VVVF control for 3-phase traction motors.
    • Increased power output (240 kW) compared to existing DC motors (187 HP) and AC motors (224 HP).
    • Roller bearings are used for axle suspension, reducing maintenance requirements compared to sleeve-type bearings.
    • Coil suspension on existing cars and air suspension on bogies enhance ride comfort and control bogie parameters under varied loads.
    • Regenerative braking (30-35% energy saving).
    • All auxiliary machines operate on 3-phase (415 V AC), reducing maintenance.
    • PLC-based control of traction/auxiliary circuits, improving reliability over relay-based systems.
    • IGBT-based static battery charger.
    • AC fans require less maintenance compared to DC fans.

    Introduction to Solid State Switching Circuits

    • Solid-state power devices minimize losses, particularly in induction motors at light/no loads.
    • Reduced losses in motors can be accomplished by adjusting the terminal voltage.
    • A power electronic circuit can adjust the motor voltage more efficiently than using an autotransformer.

    Insulator Gate Bipolar Transistor (IGBT)

    • Bipolar transistors are low-loss devices in power circuits at higher switching frequencies.
    • MOSFETs' voltage-controlled operation requires less input current, leading to simpler and cheaper triggering circuits, with lower losses, and higher switching speeds.
    • Combining MOSFETs with bipolar transistors (IGBT) improves the attributes of both, optimizing them for high voltage applications.

    Gate Turn Off Thyristor (GTO)

    • The GTO thyristor combines the advantages of conventional thyristors with high voltage switching thyristors.
    • GTO inverters have compact design and low cost due to no forced commutation circuits.
    • GTOs have higher switching speeds compared to conventional thyristors.

    Protection of dv/dt and di/dt

    • Smoothing circuits limit current and voltage transients in power electronic devices to protect them from excessive di/dt and dv/dt.
    • Snubbing inductance (Ls) limits current transients.
    • RC circuits limit voltage transients.

    Power Converters

    • Controlled rectifiers (line converters) provide a constant DC output for inverter operation.
    • Use GTO or IGBT switches for higher power factor.
    • DC link serves as a constant input for the inverter.
    • Filters (L-C filters and capacitors) smooth DC ripples; overvoltage protection provided by thyristors.
    • Inverters provide variable voltage and current at desired frequencies for AC induction motor control.

    Voltage Source Inverters

    • Voltage source inverters are the preferred choice for traction duty due to their inherent impedance and stable terminal voltages.

    Description of Electrical Power Scheme (Schematic Circuit)

    • Overhead supply (1500 V DC or 25 kV AC) is connected via a common pantograph to three sections of equipment.

    3-Phase Traction Inverter

    • Inverts 2200 V DC power to 3-phase variable voltage/variable frequency (VVVF) and supplies 4 traction motors connected in parallel.
    • Induction motors are used as traction motors.

    Diverting Chopper

    • Operates when DC link voltage exceeds a preset value.
    • Facilitates dynamic braking during regenerative braking.

    Down Chopper

    • Converts 2200 V DC to 530 V DC and supplies 3 equipment types.
    • A dedicated 20 kVA inverter powers the main compressor motor.
    • Two 50 kVA inverters convert 530 V DC to 415 V 3-phase AC (supplying auxiliary transformers).
    • Transformers provide auxiliary machine power.

    7 kW Battery Charger

    • Converts 530 V DC to 110 V DC for battery charging and control supply.

    Driving Cab Component Description

    • The primary components in the driving cab include driver control panels and the driver's control switch.

    Driver's Panel

    • A drivers control switch (DCS) enables the train function control.

    Switch Panel (BL Key Panel)

    • Consists of several switches for shunting, movement control, and safety, with various modes and states.

    Master Controller cum Brake Controller

    • The traction/brake controller distributes the traction/braking torque requests from the motorman and enables 16 positions for controlling and emergency braking.
    • Includes various brake and coasting positions and traction positions.
    • Uses a 'dead man' switch for driver safety and capability activation.
    • Mode selector facilitates train forward, neutral, or reverse motion.

    Fault Indication Panel

    • Displays various conditions, such as general faults, parking brake application, and OHE signaling.

    Pneumatic Brake Controller

    • Provides auxiliary braking capability in normal train operation.

    Driver's Display Unit

    • Displays various information, such as date, time, vehicle status, power status and fault messages.

    Instructions for Maintenance Reset

    • Cautions exist to ensure maintenance procedures are handled safely and correctly.

    Component Codes for AC-DC EMUs

    • Classification system to categorize equipment and coach types.

    Auxiliary Machines

    • Details on various auxiliary machines present in the AC/DC EMUs (e.g., fans, pumps).

    Technical Data of Electrical Equipments

    • Provides detailed data on traction transformers, line converters, inverters, and auxiliary down choppers.
    • Includes component rating values, voltages, currents, and other relevant parameters.

    Traction Motors Data

    • Data, including power, voltage, current, speed, and gear ratios for various traction motors.

    Traction Fault Data

    • Information concerning fault codes which are present in the fault system.

    Frequently Coming Message Nos.

    • List of commonly occurring fault messages, along with the relevant error codes and abbreviations.

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    Description

    This quiz explores the technical advancements in Electric Multiple Units (EMUs) that enhance performance and efficiency, particularly focusing on the shift from DC to AC induction motors. Discover the advantages of using GTO thyristors and how these innovations improve energy efficiency and passenger comfort in suburban train systems.

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