Week 10

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ih8crak
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226619
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Week 10
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2013-07-11 21:42:16
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  1. When interpreting the primary coil rating of a transformer from the name plate, which number do you use?
    The smaller one, or only one.
  2. On a transformer nameplate with two numbers listed in the primary voltage portion, what does the larger number refer to?
    The system voltage that the transformer should be installed on.
  3. What are the three primary voltage designations of transformers?
    • Phase-to-phase connection only
    • Phase-to-phase or phase-to-ground connections
    • Phase-to-ground connections only
  4. A phase-to-phase transformer connection is a _______ connection.
    Delta
  5. If a nameplate has only one number on the line for primary voltage rating, what kind of connection is it going to be?
    Delta, or Phase-to-phase
  6. Phase-to-phase connection only type transformers should not be wired phase-to-ground because they are not designed to have the rated voltage applied to one primary bushing, and ______ volts applied to the other.  Doing so will create ___________ and _________.
    • zero
    • radio interference
    • corona problems
  7. A phase-to-phase or phase-to-ground type transformer can be connected to form a _______ or _______ connection.
    • Wye 
    • Delta
  8. What is the most versatile type of transformer?
    Phase-to-phase or phase-to-ground type
  9. If the primary voltage rating of a transformer is the first number listed on a nameplate followed by the system voltage, what type of transformer is it?
    Delta (Phase-to-phase) or Wye (phase-to-ground type)
  10. If the schematic on a nameplate shows one end of the primary coil going to ground, what type of transformer is it?
    Phase-to-ground connection only type
  11. If the System voltage is listed first on a nameplate before the letters GrdY, and then the primary coil rating, what type of connection will you make?
    Phase-to-ground connection only or Wye
  12. A phase-to-ground connection is a ______ connection.
    Wye
  13. What type of transformer has only one primary bushing?
    Phase-to-ground connection only type
  14. What type of transformer has reduced insulation of the primary coil at the neutral end?
    Phase-to-ground connection only type
  15. On transformer with only one bushing on top, what is the other side of the primary winding connected to?
    It's internally grounded to the inside of the can.  The can ground is effectively the H2 bushing.
  16. The secondary coils of a single-phase transformer can be connected in ________ or _________.
    • series
    • parallel
  17. List the secondary delta voltages.
    • 120/240
    • 240/480
  18. List the secondary Wye voltages for banked transformers.
    • 120/208
    • 240/416
    • 277/480
  19. Given a single-phase transformer with a 120/240 secondary, when and why would you parallel the secondary coils?
    To give the full KVA rating of the transformer when the customer is asking for 120 V service.
  20. Inside a transformer, what marking would you find on the ends of both of the secondary coils?
    • A
    • B
    • C
    • D
  21. When paralleling the secondary coil, what is the riddle given to help you remember how to connect them?
    Alley-Cat, Bad Dog
  22. On an additive transformer, which bushings would A and C be connected to when the transformer is paralleled?
    X2
  23. On a subtractive transformer, which bushings would A and C be connected to when the transformer is paralleled?
    X1
  24. Current always flows toward ____ and _____.
    • H1
    • X1
  25. A graphical representation of voltage and connections in regard to transformers.
    Vector
  26. What does each line in a vector represent?
    A transformer winding.
  27. What are vectors commonly referred to as?
    Voltage phasors.
  28. When applying vectors to transformer banking, what is the magnitude?
    A numeric quantity of voltage.
  29. When banking transformers with a Wye connection, how many times larger will the higher of the secondary voltage be?
    1.732 times, or the 
  30. When banking transformers with a Delta connection, how many times larger will the higher of the secondary voltage be?
    2 times
  31. When drawing a vector of a Wye transformer bank, how many degrees of angle will be between the arrows showing the primary coil connections?
    120°
  32. When looking at a vector of the primaries of a transformer bank and it is a triangle, what type of connection does it represent?
    A delta connection.
  33. When connecting a transformer bank with a delta connection, what is each phase connected to?
    The H1 and H2 bushings of different cans.
  34. When connecting a transformer bank with a Wye connection, what is each phase connected to?
    A phase is connected to the H1 bushing of one can, B to another H1, and C to the 3rd can.  H2 is connected to neutral.
  35. A rise in voltage on the H1 bushing, will cause a rise on the X1 bushing, H1 and X1 will have the same _______________.
    instantaneous polarity
  36. Secondary vectors are derived from the Wye or Delta primary vectors.  As such, if the primary vector for Transformer 1 points up, which way should the secondary vector for transformer 1 face?
    Up, it should be parallel to it's corresponding vector.
  37. The voltage between the neutral and the power leg is _______ times greater than the neutral to hot leg voltage.
    1.732
  38. When banking the secondaries of a transformer in a wye configuration, the X1 bushings are connected to the hot legs and the _____ bushings are connected to neutral.
    X2
  39. When banking the secondaries of a transformer in a delta configuration, the X1 bushing of one transformer will connect to one hot leg, and the _____ will connect to another hot leg.
    X3
  40. Vectors are lines that have ________ and ________.
    • magnitude 
    • direction
  41. When the three coils of a transformer bank are each connected phase-to-phase, then the three phases are connected in ________, which is known as a delta connection.
    series
  42. When the three coils of a transformer bank are each connected phase-to-neutral, then the three coils are connected in _______, which is known as a wye connection.
    parallel
  43. What is another name for a wye connection?
    Star connection

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