Instrument Transformers in AC Circuits
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Questions and Answers

What are the two main reasons for using instrument transformers in measurement?

  • To extend the range of measuring instruments and to isolate them from high-voltage lines (correct)
  • To increase accuracy and to reduce cost of instruments
  • To decrease power consumption and to reduce size of instruments
  • To reduce power loss and to increase the safety of operators
  • What is the main advantage of using CT over shunts in ac circuits?

  • CT is cheaper than shunts
  • CT does not require careful designing of reactance and resistance proportions (correct)
  • CT is more accurate than shunts
  • CT is more reliable than shunts
  • What is a limitation of using shunts for circuits involving large current?

  • Shunts are not safe for the operator
  • The power loss in the shunt itself will become prohibitively high (correct)
  • Shunts are too expensive
  • Shunts are not accurate for large currents
  • What is a problem with using multipliers in measurement?

    <p>They can introduce errors in measurement due to inherent leakage current</p> Signup and view all the answers

    What is an advantage of using instrument transformers with ammeters?

    <p>They eliminate the need for careful designing of reactance and resistance proportions</p> Signup and view all the answers

    Why are measuring circuits involving shunts or multipliers not safe for the operator?

    <p>They are not electrically isolated from the power circuit</p> Signup and view all the answers

    What is an advantage of using a suitable multi-range CT or PT with a single-range instrument?

    <p>It allows the instrument to cover a wide range of measurement</p> Signup and view all the answers

    What is the main difference between a CT and a PT?

    <p>A CT is used for measuring current and a PT is used for measuring voltage</p> Signup and view all the answers

    What is the main reason why instrument transformers are used in measurement of voltage, current, energy, and power in ac circuits?

    <p>To extend the range of measurement and to isolate the measuring instrument from high-voltage lines</p> Signup and view all the answers

    What is a disadvantage of using multipliers in measurement?

    <p>They can introduce errors in measurement due to inherent leakage current</p> Signup and view all the answers

    Study Notes

    Instrument Transformers

    • Used in measurement of voltage, current, energy, and power in AC circuits
    • Two main reasons for use:
      • Extend (multiply) the range of measuring instruments
      • Isolate measuring instruments from high-voltage lines

    Types of Instrument Transformers

    • Current Transformer (CT): extends current ranges of instruments
    • Voltage or Potential Transformer (PT): increases voltage ranges

    Advantages of Instrument Transformers

    Over Shunts and Multipliers

    • No need for careful design of reactance and resistance proportions for shunts and meters
    • Can be used for circuits involving large currents without excessive power loss
    • No introduction of errors in measurement due to leakage current
    • No unnecessary heating due to power loss
    • Electrically isolated from power circuit, ensuring operator safety
    • Can cover a wide range of measurements with single-range, moderate-sized instruments
    • Can reduce overall cost by connecting multiple instruments to the same instrument transformer

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    Description

    Learn about the use of instrument transformers in measuring voltage, current, energy, and power in AC circuits. Understand their importance in extending measurement ranges and isolating instruments from high-voltage lines.

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