Transformer Step-Down Ratios Quiz
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Questions and Answers

What is the voltage ratio of a transformer with a primary voltage of 30 V and a secondary voltage of 90 V?

  • $rac{30}{90}$
  • $rac{90}{30}$
  • $3$ (correct)
  • $rac{1}{3}$
  • What is the name of a transformer where the voltage across the secondary is less than the voltage across the primary?

  • Voltage ratio transformer
  • Proportional transformer
  • Step-down transformer (correct)
  • Step-up transformer
  • What is the ratio of a four-to-one step-down transformer?

  • 6:1
  • 1:6
  • 4:1 (correct)
  • 1:4
  • What type of transformer has fewer turns in the primary than in the secondary?

    <p>Step-up transformer</p> Signup and view all the answers

    What is the name of a transformer where the voltage across the secondary is greater than the voltage applied to the primary?

    <p>Step-up transformer</p> Signup and view all the answers

    What is the correct way to write the ratio of a one-to-four step-up transformer?

    <p>1:4</p> Signup and view all the answers

    What is the main difference between an IDG and a CSD?

    <p>An IDG contains both the CSD and the AC generator in the same housing, while a CSD does not.</p> Signup and view all the answers

    What is the purpose of the 'generator' term being used for IDGs, even though they are actually brushless alternators?

    <p>It is a historical term that has not been updated.</p> Signup and view all the answers

    What is the main advantage of AC motors compared to DC motors?

    <p>AC motors require less maintenance due to the lack of brushes and commutators.</p> Signup and view all the answers

    Which of the following is a method of producing a rotating field in an AC motor?

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

    What is the relationship between the primary and secondary voltages in a step-up transformer?

    <p>The secondary voltage is greater than the primary voltage.</p> Signup and view all the answers

    What is the relationship between the primary and secondary turns in a step-down transformer?

    <p>The primary has more turns than the secondary.</p> Signup and view all the answers

    What is the primary function of the permanent magnetic field in a brushless alternator?

    <p>To provide the initial magnetic flux to start the generator</p> Signup and view all the answers

    What is the purpose of the generator control unit (GCU) in a brushless alternator?

    <p>To rectify the AC output from the armature and supply it to the exciter field winding</p> Signup and view all the answers

    What is the role of the six silicon diodes in a brushless alternator?

    <p>To rectify the DC output from the exciter output winding and supply it to the output field winding</p> Signup and view all the answers

    Which of the following components in a brushless alternator rotate as a unit?

    <p>The permanent magnet, exciter output winding, six diodes, and output field winding</p> Signup and view all the answers

    What is the purpose of the laminated frame in the alternator housing?

    <p>To house the three-phase output stator windings</p> Signup and view all the answers

    In a brushless alternator, which component induces voltage into the main output coils?

    <p>The output field winding</p> Signup and view all the answers

    What are the two mechanical parts that all generators must have for relative motion to take place between the conductor and the magnetic field?

    <p>Stator and rotor</p> Signup and view all the answers

    In a DC generator, which part is always the armature?

    <p>The rotor</p> Signup and view all the answers

    In an alternator, which part may be the armature?

    <p>Both the rotor and the stator</p> Signup and view all the answers

    What is the main difference between a revolving-armature alternator and a DC generator?

    <p>The alternator generates AC, while the DC generator generates DC</p> Signup and view all the answers

    What is the main advantage of the revolving-field type alternator over the revolving-armature type?

    <p>It is used almost exclusively in aircraft</p> Signup and view all the answers

    What is the total circuit resistance in the given example?

    <p>$24 \Omega$</p> Signup and view all the answers

    What is the circuit current in the given example?

    <p>$1 A$</p> Signup and view all the answers

    What is the power dissipated in the source in the given example?

    <p>$6 W$</p> Signup and view all the answers

    What is the power dissipated in the load in the given example?

    <p>$18 W$</p> Signup and view all the answers

    According to the maximum power transfer graph summary, in which region should the load resistance be less than the source resistance?

    <p>Region 1</p> Signup and view all the answers

    What is the formula for calculating the turns ratio of a transformer used for impedance matching?

    <p>$T^2 = \frac{Z_P}{Z_S}$</p> Signup and view all the answers

    Study Notes

    Transformers

    • A transformer with a turn ratio of 6:1 means the primary has 6 times the number of turns as the secondary.
    • A step-down transformer has a lower voltage across the secondary than the primary, with a ratio written as 4:1.
    • A step-up transformer has a higher voltage across the secondary than the primary, with a ratio written as 1:4.
    • The voltage ratio of a transformer is the ratio of the primary voltage to the secondary voltage (VS/VP).

    IDG (Integrated Drive Generator)

    • An IDG is a type of generator that contains a CSD (Constant Speed Drive) and an AC generator in the same housing.
    • IDGs are actually brushless alternators, despite being called generators.

    AC Motors

    • Advantages of AC motors include lower cost and less maintenance due to the lack of brushes and commutators.
    • Methods of speed control and direction of rotation will be described.
    • Rotating fields can be produced using capacitors, inductors, or shaded or split poles.

    Brushless Alternator

    • A brushless alternator has a permanent magnetic field, an exciter field, and a main output field.
    • The permanent magnets start the generator, producing an output before field current flows.
    • The magnetic field induces voltage into an armature, which is sent to the generator control unit (GCU).
    • The GCU rectifies the AC and sends it to the exciter field winding.

    AC Motor Theory

    • AC motors can be synchronous or induction motors, and can be single-phase or polyphase.
    • Synchronous motors have a rotor and a stator, with the rotor rotating and the stator remaining stationary.
    • Induction motors have a rotating field that induces voltage into the stator.

    Alternators

    • Alternators can be revolving-armature or revolving-field type.
    • Revolving-armature alternators have a rotor that is the armature and a stator that is the field.
    • Revolving-field alternators have a rotor that is the field and a stator that is the armature, commonly used in aircraft.

    Power Transfer and Impedance Matching

    • Maximum power transfer occurs when the load resistance equals the source resistance.
    • Minimum heat generated in the source occurs when the load resistance is less than the source resistance.
    • Impedance matching is important for connecting sources and loads of dissimilar impedance, and can be done using a transformer.
    • Transformers can be used to match impedances without losing power.

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    Related Documents

    Transformers I (3.15) PDF

    Description

    Test your knowledge on step-down transformer ratios and voltage calculations. Learn how to determine the number of turns in the primary and secondary sides based on the given ratio.

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