Electrical Transformers: Copper and Hysteresis Losses
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Questions and Answers

How do the thin, insulated laminations in the transformer core help reduce eddy current losses?

  • They increase the resistance of the core material
  • They increase the magnetic permeability of the core
  • They create an easy path for current to flow through
  • They do not provide an easy path for current, reducing eddy currents (correct)

    • What is the primary reason for laminating transformer cores?

  • To increase the core's magnetic permeability
  • To minimize eddy current losses (correct)
  • To reduce the weight of the transformer
  • To increase the transformer's efficiency

    • If the input power to a transformer is 650 W and the output power is 610 W, what is the efficiency of the transformer?

  • 93.8% (correct)
  • 92%
  • 95%
  • 90%

    • How can the power loss in a transformer be calculated?

    <p>By subtracting the output power from the input power</p> Signup and view all the answers

    What is the primary purpose of a transformer?

    <p>To increase the voltage of an AC power source</p> Signup and view all the answers

    What is the primary method for minimizing copper losses in a transformer?

    <p>Increasing the diameter of the wire used in the primary and secondary windings</p> Signup and view all the answers

    Which of the following factors contribute to hysteresis losses in a transformer?

    <p>The core material and the frequency of the applied current</p> Signup and view all the answers

    What is the primary reason for using laminated cores in transformers?

    <p>To minimize eddy current losses</p> Signup and view all the answers

    Which type of transformer has no hysteresis losses?

    <p>Air-core transformers</p> Signup and view all the answers

    What is the primary effect of eddy currents in a transformer core?

    <p>They increase the magnetizing current required</p> Signup and view all the answers

    Which core material is best suited for minimizing hysteresis losses in a transformer?

    <p>Supermalloy (iron-nickel-molybdenum alloy)</p> Signup and view all the answers

    What is the impedance transformation ratio of the transformer?

    <p>16:1</p> Signup and view all the answers

    If the primary winding has a resistance of 25 Ω, what is the equivalent resistance of the secondary winding?

    <p>1.5625 Ω</p> Signup and view all the answers

    If the primary winding is rated for a maximum voltage of 200 V, what is the maximum voltage that can be safely applied to the secondary winding?

    <p>50 V</p> Signup and view all the answers

    Which of the following factors determines the maximum current that can be carried by a transformer winding?

    <p>The diameter of the wire used for the winding</p> Signup and view all the answers

    If the transformer is operating at 100% efficiency, what is the power relationship between the primary and secondary windings?

    <p>The power in the primary winding is equal to the power in the secondary winding.</p> Signup and view all the answers

    Which of the following statements about transformer ratings is true?

    <p>The maximum voltage that can be applied to a winding is determined by the type and thickness of the insulation used between the windings.</p> Signup and view all the answers

    What is the purpose of impedance matching?

    <p>To ensure maximum power transfer to the load</p> Signup and view all the answers

    In the first example given, where the source impedance is 6 Ω and the load impedance is 2 Ω, what is the power dissipated in the source?

    <p>54 W</p> Signup and view all the answers

    What is the total circuit resistance in the second example, where the source impedance and load impedance are both 6 Ω?

    <p>6 Ω</p> Signup and view all the answers

    If the load impedance is equal to the source impedance, what is the ratio of power dissipated in the source to power delivered to the load?

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

    What is the circuit current in the second example, where the source voltage is 24 V and the total circuit resistance is 12 Ω?

    <p>2 A</p> Signup and view all the answers

    If the load impedance is greater than the source impedance, what happens to the power transfer efficiency?

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

    What type of transformer configuration is described where a single coil of wire is 'tapped' to produce a primary and secondary winding?

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

    In an auto-transformer with an adjustable tap, when the tap is at point A, how does the secondary voltage (Es) compare to the primary voltage (Ep)?

    <p>Es is less than Ep</p> Signup and view all the answers

    If a voltage of 200 V is applied between points B and C in an auto-transformer, what is the secondary voltage available from points A and B?

    <p>100 V</p> Signup and view all the answers

    What is the voltage available from points A and C in the auto-transformer, if a voltage of 200 V is applied between points B and C?

    <p>300 V</p> Signup and view all the answers

    Which of the following is a brand name commonly used for adjustable auto-transformers?

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

    Under what condition can a transformer be used at frequencies above its normal operating frequency?

    <p>For any frequency above its normal operating frequency</p> Signup and view all the answers

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