Power Converters for Traction Motors
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Questions and Answers

What is the primary function of the traction converter in relation to the traction motors?

  • To increase the frequency of the voltage output.
  • To continuously adjust the driving or braking torque. (correct)
  • To limit the overvoltage of the electrical system.
  • To convert single-phase energy into three-phase energy.

    • Which component is part of the Line Converter?

  • Oil-cooled valve set. (correct)
  • Over voltage limitation resistor.
  • DC-link capacitor bank.
  • Charging resistor.

    • What role do the traction motors play during electric braking?

  • They act as resistors to dissipate energy.
  • They directly convert energy into mechanical torque.
  • They function as generators to produce energy. (correct)
  • They increase the vehicle speed during braking.

    • Which of the following is responsible for monitoring the DC-link voltage?

    <p>Voltage transducers.</p> Signup and view all the answers

    What type of energy conversion occurs when traction motors are engaged in regenerative braking?

    <p>From three-phase to single-phase energy.</p> Signup and view all the answers

    Which component in the traction converter is specifically meant for overvoltage protection?

    <p>Over voltage limitation resistor.</p> Signup and view all the answers

    What is the primary role of the DC-link in a traction converter system?

    <p>To stabilize voltage levels between components.</p> Signup and view all the answers

    What happens to the converter when the main circuit breaker is opened?

    <p>The converter is powered down.</p> Signup and view all the answers

    Which condition is NOT a reason for powering down the converter?

    <p>The demanded torque is increased.</p> Signup and view all the answers

    What is the primary purpose of the five-stage protection concept for the converter?

    <p>To prevent damage to important components.</p> Signup and view all the answers

    What key aspect is monitored in protection stage 1 of the converter?

    <p>Minimum switching times of the GTO-thyristors.</p> Signup and view all the answers

    How does protection stage 1 prevent shorting of the DC-link?

    <p>By interlocking firing signals of GTO-thyristor pairs.</p> Signup and view all the answers

    What triggers the firing of the GTO in the overvoltage limitation circuit?

    <p>When the capacitance of A31 is insufficient</p> Signup and view all the answers

    Which of the following is not a cause of overvoltages in the DC-link?

    <p>DC-link capacitance increase</p> Signup and view all the answers

    What is the resistance value of the MUB-resistor?

    <p>2.5 mΩ</p> Signup and view all the answers

    How is the DC-link charged during operation?

    <p>From the pulse-controlled three-phase bridge circuit</p> Signup and view all the answers

    What monitoring function is included in the DC-link's system?

    <p>Earth fault monitoring</p> Signup and view all the answers

    Which component is responsible for discharging the converter DC-link when the vehicle is powered down?

    <p>The MUB-circuit</p> Signup and view all the answers

    What is the relationship between frequency and amplitude in the motor converter operation?

    <p>They can be changed independently</p> Signup and view all the answers

    Which of the following describes the output voltage of the three-phase bridge circuit?

    <p>Square pulses of constant amplitude</p> Signup and view all the answers

    What is the purpose of the voltage indicator H08?

    <p>To show DC voltage measurements for converter control</p> Signup and view all the answers

    What happens to the fundamental frequency of motor terminal voltage during motoring mode?

    <p>It is higher than the frequency corresponding to the motor speed.</p> Signup and view all the answers

    During braking, what occurs with the fundamental frequency of motor terminal voltage?

    <p>It decreases below the frequency corresponding to the motor speed.</p> Signup and view all the answers

    What is the primary method employed in the ISR range for controlling motor voltage?

    <p>Pulse-width modulation.</p> Signup and view all the answers

    What is the range of the TB-DSR control method in terms of motor voltage?

    <p>30% to 98% of nominal voltage.</p> Signup and view all the answers

    In the ISR range, what is true about the torque produced by the motors?

    <p>It can be loaded with nominal torque over the entire range.</p> Signup and view all the answers

    In the TB-DSR range, how is the torque controlled?

    <p>To a user-defined set value.</p> Signup and view all the answers

    What aspect of the motor converter is optimized in TB-DSR?

    <p>Managing switching frequency for reduced torque pulsations.</p> Signup and view all the answers

    What is the result of positive slip in a motor?

    <p>It generates positive motor torque.</p> Signup and view all the answers

    What characterizes the ISR range in terms of GTO-switching frequency?

    <p>It remains constant throughout the range.</p> Signup and view all the answers

    What is a key characteristic of square-wave operation in relation to the DSR?

    <p>It incorporates a field-weakening mechanism.</p> Signup and view all the answers

    What is the primary effect of changing the frequency in the field weakening range?

    <p>Inversely proportional relationship with motor flux</p> Signup and view all the answers

    Which component has no hand-operated functionality in the traction converter system?

    <p>Earthing switch Q21</p> Signup and view all the answers

    How is the control electronics of the traction converter structured?

    <p>Completely reliant on microprocessors</p> Signup and view all the answers

    What role does the FLG (vehicle control unit) play in the traction converter system?

    <p>Calculates required tractive or braking effort</p> Signup and view all the answers

    What mathematical relationship defines the demanded torque in the system?

    <p>A function of driving speed and effective load torque</p> Signup and view all the answers

    In square-wave operation, how is the line-line motor voltage formed?

    <p>By one voltage pulse per half-wave</p> Signup and view all the answers

    What does the SLG (converter control unit) do with the demanded torque from the FLG?

    <p>Compares it with the effective load torque</p> Signup and view all the answers

    Which of the following statements about field weakening is true?

    <p>It is the range between nominal and maximum speed</p> Signup and view all the answers

    What is the primary function of traction converters in the system?

    <p>To convert driver inputs into motor control values</p> Signup and view all the answers

    What serves as a communication medium between the various control units in the system?

    <p>Data bus system (MICAS vehicle bus)</p> Signup and view all the answers

    What is the primary source of power pulsations that the DC-link must compensate for?

    <p>Irregularities caused by wheel spin and pantograph bounce</p> Signup and view all the answers

    Why is the DC-link capacitor designed to absorb harmonic currents?

    <p>To prevent unacceptable fluctuations in DC-link voltage</p> Signup and view all the answers

    What frequency must the A33-L02 series resonant circuit be tuned to in order to filter out unwanted current?

    <p>Double the line frequency</p> Signup and view all the answers

    What characteristic of power equilibrium is noted in the DC-link operation following disturbances?

    <p>There is an inherent delay in recovering power equilibrium</p> Signup and view all the answers

    How does the DC-link primarily handle the power needs of the motor converter?

    <p>By supplying almost pure DC current to the motor converter</p> Signup and view all the answers

    During operation, what causes the DC-link to experience non-periodic power differences?

    <p>Harmonic currents produced by both the line and motor converters</p> Signup and view all the answers

    What effect does the single-phase operation of the line converter have on the DC-link?

    <p>It creates relatively low frequency power pulsations</p> Signup and view all the answers

    What is required for the successful initiation of the ON-LINE test?

    <p>The OFF-LINE test must be successfully completed.</p> Signup and view all the answers

    During which phase are the GTO-thyristors’ control pulses released for the motor converter?

    <p>200 ms after the K11 main contactor is closed.</p> Signup and view all the answers

    Which function is evaluated during the OFF-LINE test?

    <p>The gate unit supply voltages.</p> Signup and view all the answers

    Which of the following conditions is NOT necessary for releasing the GTO control pulses?

    <p>The GTO-thyristors must already be in a conductive state.</p> Signup and view all the answers

    Which parameter is continuously monitored during the ON-LINE test?

    <p>The operational readiness of the MUB.</p> Signup and view all the answers

    What event causes the GTO in the R71 overvoltage limitation resistor to fire?

    <p>Once a preset overvoltage threshold is exceeded.</p> Signup and view all the answers

    Which factor is NOT a cause of overvoltages in the DC-link?

    <p>Ground fault current</p> Signup and view all the answers

    What is the primary purpose of the MUB circuit?

    <p>To discharge the converter DC-link when power is lost.</p> Signup and view all the answers

    In the motor converter, how are the three-phase AC voltages generated?

    <p>Using a pulse-controlled three-phase bridge circuit.</p> Signup and view all the answers

    How does the MUB-resistor's specification of 2.5 mΩ impact the circuit?

    <p>It minimizes the power loss during high voltage conditions.</p> Signup and view all the answers

    What is a characteristic of the AC voltage produced by the motor converter?

    <p>It consists of square pulses of constant amplitude.</p> Signup and view all the answers

    What role does the earth fault monitoring system (U05, R51 + R52) play in the control of the DC-link?

    <p>It detects potential ground faults to protect the system.</p> Signup and view all the answers

    How is the torque of the motors controlled in relation to the pulse-shaped motor-phase voltages?

    <p>Through continuous changes in frequency and amplitude.</p> Signup and view all the answers

    What occurs to the motor flux as the frequency is increased in the field weakening range?

    <p>It decreases inversely proportional.</p> Signup and view all the answers

    What is the primary function of the control electronics within the traction converters?

    <p>To provide continuous, automated control of motor parameters.</p> Signup and view all the answers

    In the motor converter control system, what compares the demanded torque with the effective load torque?

    <p>Converter control unit (SLG).</p> Signup and view all the answers

    What is indicated by the term 'square-wave operation' in relation to the traction motors?

    <p>It generates a single voltage pulse per half-wave.</p> Signup and view all the answers

    How does the vehicle control unit (FLG) react to demands from the driver's cab?

    <p>It calculates required voltage, current, and frequency values.</p> Signup and view all the answers

    Which statement best describes the relationship between motor voltage and frequency during the field weakening range?

    <p>Voltage amplitude is constant while frequency changes.</p> Signup and view all the answers

    What component is not found in the traction converter system as a manual control?

    <p>Earthing switch Q21.</p> Signup and view all the answers

    What microprocessor-based system underlies the control electronics of the traction converter?

    <p>MICAS vehicle bus.</p> Signup and view all the answers

    What mathematical calculation is performed by the FLG in relation to the vehicle speed?

    <p>It calculates the required tractive or braking effort.</p> Signup and view all the answers

    During field weakening, what happens to the pullout torque as frequency increases?

    <p>It decreases inversely proportional.</p> Signup and view all the answers

    How does the ALG influence the firing of GTO-thyristors?

    <p>It determines the required firing pulses based on the demanded torque.</p> Signup and view all the answers

    What is the primary role of the GTO feedback signals in the system?

    <p>To monitor operation and ensure firing conditions are met.</p> Signup and view all the answers

    In what scenario does the line converter reduce the DC-link voltage?

    <p>When the power demand is below the rated value.</p> Signup and view all the answers

    What happens during the automatic system tests performed by the converter?

    <p>Regular checks are conducted whenever the vehicle is powered-up.</p> Signup and view all the answers

    Which functions are performed by both the vehicle control unit and the converter control unit?

    <p>Automatic powering-up and powering-down based on driver selection.</p> Signup and view all the answers

    How does the ALG ensure synchronization between the line converter and the motor converter?

    <p>By ensuring the flow of active power has the same value and direction.</p> Signup and view all the answers

    What is required for the firing of a GTO-thyristor according to the monitoring system?

    <p>Fulfillment of necessary conditions verified by feedback.</p> Signup and view all the answers

    What occurs if a GTO fails during operation in the traction converter?

    <p>The converter is shut down or not powered-up immediately.</p> Signup and view all the answers

    What is the significance of the Gate Unit Power Supply A08 (GUSP)?

    <p>It provides energy required for the Gate Units to function.</p> Signup and view all the answers

    What condition is triggered for the automatic tests of the converter?

    <p>When the vehicle is first powered-up or after a protective shut-down.</p> Signup and view all the answers

    Study Notes

    Power Converter Introduction

    • Three-phase voltage for traction motors is generated on the vehicle by two traction converters
    • Converters are connected between the main transformer and the traction motors
    • Frequency and amplitude of the three-phase converter output voltage are continuously adjusted based on driver demands
    • This allows for smooth adjustment of driving or braking torque
    • Electrical braking uses the traction motors as generators
    • Regenerative braking converts three-phase electrical energy back into single-phase energy

    Converter Structure and Components

    • Line Converter (A11, A12): Oil-cooled valve sets with two pairs of arms each (2xZV24(12))
    • A111-A114, A121-A124: Gate Units (forced air cooling) (227)
    • K01: Charging contactor
    • K11: Converter contactor
    • R04: Charging resistor
    • U11-U14: Current transducers (18.2)

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    Description

    This quiz covers the basic principles and components of power converters used in traction motors, focusing on three-phase voltage generation and regenerative braking. It explores how converters function between the main transformer and traction motors while adjusting output voltage based on driver demands. Test your understanding of converter structures and their integral parts.

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