[工学]Ch5_第五章 diode rectifiers.ppt

We have some conclusions as bellows: For a given frequency ω, the commutation interval u increases with Ls and decreases with increasing voltage Vs; The finite commutation interval reduces the average value of the output voltage. With Ls=0 With infinite Ls The reduction in the average output voltage by △Vd from Vd0 is: The internal resistance of the source: Note: There are not any active power dissipations through the Xs. Current Commutation in Full-Bridge Rectifier During the commutation interval: The volt-radian area Au: So, the commutation interval can be calculated: When Ls=0: With Ls=0 With infinite Ls The reduction in the average output voltage by △Vd from Vd0 is: The internal resistance of the source: Note: There are not any active power dissipations through the Xs. 5-3-3 Constant dc-side voltage vd(t)=Vd Rectifier with a dc-side voltage DC-Side Voltage and Current Relationship Zero current corresponds to dc voltage equal to the peak of the input ac voltage Effect of DC-Side Current on THD, PF and DPF Very high THD at low current values Crest Factor versus the Current Loading The Crest Factor is very high at low values of current Diode-Rectifier with a Capacitor Filter Power electronics load is represented by an equivalent load resistance Diode Rectifier Bridge Equivalent circuit for analysis on one-half cycle basis Diode-Bridge Rectifier: Waveforms Analysis using MATLAB Diode-Bridge Rectifier: Waveforms Analysis using PSpice Analysis using PSpice Input Line-Current Distortion Line-Voltage Distortion PCC is the point of common coupling Distortion in voltage supplied to other loads Line-Voltage Distortion 5-4 Voltage doubler (single-phase) rectifiers Voltage Doubler Rectifier In 115-V position, one capacitor at-a-time is charged from the input. 5-5 Effect of single-phase rectifiers on neutral currents in three-phase, four-wire systems * 5-* * 5-* Chapter 5 Line-frequency diode rectifiers: line-frequency ac →uncontrolled dc 5-1 Introduction