Harmonics2-1.txt

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johnbowens
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125353
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Harmonics2-1.txt
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2011-12-30 02:08:13
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harmonics JATC IBEW electrical transformers
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ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics (NC set 2)
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  1. Total Harmonic distortion (THD) is what? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics, PP 10 (NC set 2)
    What is the amount of harmonics on aline compared to the fundamental frequency of 60 Hz.
  2. Voltage THD (total harmonic distortion) is caused by what? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    Harmonic currents on the line create this.
  3. High-voltage distortion is a problem because of what? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    Because voltage distortion becomes a carrier for harmonics to Linear loads such as motors.
  4. For best results, the voltage and current THD (total harmonic distortion) should not exceed what percent of the fundamental frequency? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    • Voltage THD 5%
    • Current THD 20%
  5. Where should THD (total harmonic distortion) be measured at? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    THD should be measured at the transformer.
  6. TDD, total demand distortion is what ratio? ATP & NJATC, Transformer Principles & Applications, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    TDD is the ratio of the current harmonics to the maximum load current.
  7. How is TDD (total demand distortion) and THD (total harmonic distortion) different? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 103 (NC set 2)
    TDD is referenced to the maximum current measurement taken over time.
  8. Any AC circuit consists of what four elements of power? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    Real, reactive, harmonic, and apparent.
  9. What shows up as a phase displacement between the current and voltage waveforms? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    Reactive power.
  10. Apparent power is the power, and VA or kVA and is the sum of what? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    Apparent power is the sum of true power, reactive power, and harmonic power.
  11. Displacement power factor is what? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    The ratio of true power to apparent power due to the phase displacement between the current and voltage.
  12. What can usually be added to a circuit to correct displacement power factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    Capacitors can usually be added to the circuit or distribution system to correct this.
  13. What is the formula for displacement power factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    It is the same as the standard power factor formula, and is due to the phase displacement between the current and voltage.
  14. What is displacement power factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    • The ratio of true power to apparent power due to THD.
  15. What cannot be added to a circuit or distortion system to compensate for distortion power factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
    Capacitors cannot be added to correct this.
  16. Distortion power factor is calculated by what formula? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105
  17. Total power factor is the product of what? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 105 (NC set 2)
  18. What may cause reset and loss of data in computer systems? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP105 (NC set 2)
    Sags and swells may cause this because of insufficient peak voltage to keep the capacitor charged in an SMPS.
  19. It is important to know power factor because it relates to apparent power which is used to size what? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 106 (NC set 2)
    The elements of a power distribution system is sized by this.
  20. What is current crest factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 106 (NC set 2)
    • The peak value of waveform divided by the RMS value of the waveform.
  21. The UPS can supply what crest factor at full load? how does this relate to lower loads? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 107 (NC set 2)
    • UPS has a crest factor of three at full load, but can supply a higher crest factors at lower loads.
  22. A smoothing capacitor has an extended charge time that has what effect on the crest factor? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 107 (NC set 2)
    • This reduces the crest factor.
  23. Harmonic distortion is created by computers, printers, electronic ballasts, and name two more. ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 107 (NC set 2)
    Variable speed motor drives and medical test equipment.
  24. A switch mode power supply is a power supply for electronic devices that does what? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 107 (NC set 2)
    • Quickly switches the load current on and off in order to deliver a stable output voltage.
  25. A typical single phase SMPS is designed to use what immediately after the AC power supply? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 108 (NC set 2)
    • A full wave bridge rectifier.
  26. With a smoothing capacitor, current flows during what part of the cycle? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 108 (NC set 2)
    Where the voltage exceeds the minimum value, this occurs with a smoothing capacitor.
  27. Flat-topping occurs when? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 108 (NC set 2)
    When many loads draw current in pulses at the maximum voltage level and overload the power source, this occurs.
  28. Why are loads characterized as nonlinear? ATP & NJATC, Transformer Principles & Application, 2006: Chapter 5-Harmonics PP 108 (NC set 2)
    When the input current is significantly distorted as compared to the ideal current waveforms.

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