POWER ELECTRONICS
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Transcript of POWER ELECTRONICS
POWER ELECTRONICS
Instructor: Eng.Moayed N. EL Mobaied
The Islamic University of GazaFaculty of EngineeringElectrical Engineering Department
الرحمن الله بسمالرحيم
EELE 5450 — Fall 2009-2010
Lecture 27
Three switches conducting
The conducting sequence is as follows (each device conducts for a 180o period):
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
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
Comparing rms line currents
Comparing rms line currents
Two switches conducting
INVERTER HARMONICS
INVERTER HARMONICS
INVERTER HARMONICS
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 eachhalf-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.
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.
SINUSOIDAL PULSE-WIDTH MODULATION
End of Lecture
Problem set : (SELF-ASSESSMENT TEST, PROBLEMS) due to 6/1/2010