3-Phase rectification & Ripple

[SG-1]

Thanks Everyone

Thanks Everyone

Thanks to everyone that replied.

 

[PaulWDent]

I need a formula to calculate the AC ripple for an unfiltered 3-Phase Bridge ( 6 pulse ). The only formulas I can find are for circuits with a smoothing capacitor.

Maybe I could just use an ungodly small capacitor for the calculation...??

The final intent of this exercise is to be able to measure the ripple to determine the health of the diode bridge. The supply is variable 0 - 300 VDC.

Delta fed , 6-diode 3=phase bridge(no neutral): There is one diode from each line with its cathode to the positive DC output, and one diode from each line with its anode to the negative DC output. This arrangement has ripple on both the posiitve output and the negative output. The peak is root(2) =1.414 times the rms line voltage and the trough is 1/root(2) = 0.707 times the line voltage, and the frequency is 180Hz.
But, since the peak on + corresponds to the trough on -, the difference between them shows less ripple. The plus-to-minus differential DC voltage has a peak of root(6)=2.45 times the rms line voltage, and a trough of 1.5Root(2) = 2.22 times the rms line voltage at a frequency of 360Hz.
Note that the 180HZ component of the ripple has vanished from the differential voltage; this is becauise it is in-phase on both the + and -, and is a COMMON MODE ripple. This may or may not affect your application. I will try and attach a spread sheet that plots it.

 

[PaulWDent]

Wouldnlt let me paste the spread sheet.I'll try the graphs

Wouldnlt let me paste the spread sheet.I'll try the graphs