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POWER ELECTRONICS

بسم الله الرحمن الرحيم. The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department. POWER ELECTRONICS. EELE 5450 — Fall 2009-2010. Instructor: Eng.Moayed N. EL Mobaied. Lecture 27. Three switches conducting.

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POWER ELECTRONICS

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  1. بسم الله الرحمن الرحيم The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department POWER ELECTRONICS EELE 5450— Fall 2009-2010 Instructor: Eng.Moayed N. EL Mobaied Lecture 27

  2. Three switches conducting The conducting sequence is as follows (each device conducts for a 180o period):

  3. Three conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120o

  4. Three conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120o

  5. Comparing rms line currents

  6. Comparing rms line currents Two switches conducting

  7. INVERTER HARMONICS

  8. INVERTER HARMONICS

  9. INVERTER HARMONICS

  10. SINUSOIDAL PULSE-WIDTH MODULATION One of the methods used to reduce the low frequency harmonics in the inverter waveform is sinusoidal pulse-width modulation. In this method, a reference copy of the desired sinusoidal waveform, the modulating wave, is compared to a much higher frequency triangular waveform, called the carrier wave The resulting drive signals cause multiple turn-on of the inverter switches in each half-cycle with variable pulse width to produce a quasi-sine wave of load voltage. The pulse width increases from a very narrow width at the start of each cycle to a maximum width in the middle of each cycle. Then the pulse width reduces again after maximum until its minimum width at the end of the half-cycle period.

  11. SINUSOIDAL PULSE-WIDTH MODULATION Typically in the comparator when the sine wave voltage exceeds the triangular wave voltage, the load voltage is +Vdc, and when the triangular wave voltage exceeds the sine wave voltage, the load voltage is -Vdc.

  12. SINUSOIDAL PULSE-WIDTH MODULATION Problem set : (SELF-ASSESSMENT TEST, PROBLEMS) due to 6/1/2010 End of Lecture

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