Generators Part II (NAVEDTRA 14177A Pages 24-45)

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  1. Of what is the core of a generator armature made?
    Soft iron, which is a conducting material with desirable magnetic characteristics.
  2. What are the currents that are induces in the generator armature core called?
    Eddy Currents
  3. Some armature cores are made of a solid piece of soft iron, but some are made up of several small pieces insulated from each other.  What is this process called?
  4. How thin may the laminations in a small generator armature be?
    1/64 inch
  5. Why do most generators use armatures with laminated cores?
    To reduce eddy current losses
  6. What is hysteresis loss?
    A heat loss caused by the magnetic properties of the armature
  7. To compensate for hysteresis losses, what are used in most DC generator armatures?
    heat-treated silicon steel laminations
  8. How does the construction of a practical DC generator differ from the elementary generator?
    In the construction of the armature, the manner in which the armature is wound, and the method of developing the main field
  9. The commutator in a practical generator differs from the elementary generator in what way?
    The number of segments must equal the number of armature coils.
  10. In a GRAMME-RING armature, how many commutator segments are attached to each coil?
  11. The total voltage induced is greater in which armature--the DRUM-TYPE or the GRAMME-RING?
  12. Which two types of windings may be used for a drum-type armature?
    • 1) Lap Winding
    • 2) Wave Winding
  13. When a DC voltage is applied to the field windings of a DC generator, current flows through the windings and sets up a steady magnetic field.  What is this called?
    Field Excitation
  14. Field excitation voltage can be produced by the generator itself, or it can be supplied by an outside source, such as a battery.
    What is a generator called that supplies its own field excitation?
    • A self-excited generator.
    • Note: This is possible only if the field pole pieces have retained a slight amount of permanent magnetism, called residual magnetism.
  15. Self-excited generators are classed according to the type of field connection they use.  What are the 3 general types?
    • 1) Series-wound
    • 2) Shunt-wound (parallel)
    • 3) Compound-wound
  16. Voltage control is either:
    • 1) Manual
    • 2) Automatic
  17. What is parallel operation of generators?
    When 2 or more generators are supplying a common load
  18. What are special-purpose DC generators?
  19. The amplidyne is really 2 things in 1.  What are they?
    A constant-speed AC motor (the prime mover) mechanically coupled to a DC generator
  20. In the amplidyne generator, what is the equation to find gain?
  21. When does magnetic induction take place?
    When a conductor is moved in a magnetic field in such a way that it cuts flux lines, and a voltage (emf) is induced in the conductor.
  22. What is the Left-Hand Rule for Generators?
    When the thumb, forefinger, and middle finger of the left hand are extended at right angles to each other, so that the indicates the direction of movement of the conductor in the magnetic field, and the forefinger points in the direction of the flux lines (north to south), the middle finger shows the direction of induced emf in the conductor.
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Generators Part II (NAVEDTRA 14177A Pages 24-45)
2014-01-29 07:06:37
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