AC to DC rectification

[Besoeker]

Hi everybody ,

Does any one knows the calculation of The 3 Phase Silicon-Controlled Rectifier .

I saw one rectify 600 VAC to 750 VDC .
so,
750/600=(1.25 --->is this factor .) if yes from where we get this factor mathematically.


Regards.

As others have pointed out, the DC output depends on conduction angle.
Fully phased on, the maximum mean voltage is 1.35*Vrms

 

[G._S._Ohm]

750/600=(1.25 --->is this factor .) if yes from where we get this factor mathematically.

I get 95% of peak value, 848 volts in this case so you get 808 vdc for the unfiltered DC output with all SCRs fully turned on and neglecting the drop across each SCR.
With filtering you can go to about 848 VDC depending on how much ripple you have.

 

[G._S._Ohm]

As to the calculation, the DC value of the 3 phase rectified sinewave is found by dividing the area under the curve [found by integration] by the base width of the sine pulse.
For 3 phase, it looks like you want to find the area under the center 120 degrees of a half sine pulse. This is the base width.

It's a bit hard to explain. . .

 

[Besoeker]

Not sure where the 1.35 factor comes from,

Take this waveform:

Note that it has six pulses per cycle of the fundamental and that each is symmetrical about the peak. So you can calculate average voltage like this.

Second line is a bit messy - I'm still not up to speed with the newer version of equation editor. It would have be much quicker just to have written it out and scanned it.

You can also do it over the duration of one complete pulse and get 3Vm/pi integrated from pi/3 to 2pi/3 and get the same result.

Anyway, that's where the 1.35 comes from.

 

[R o y a l]

Thanks a lot.

Thanks a lot.

Gents,


I really appreciate.

Besoeker,

Thank you so much