Have 3 caps, which one to use?

[juxtoposed]

I have a 34 volt 21 amp transformer and I have three caps but don't know which would be "best" to use.

1 16000 MFD 75 VDC surge 95 VDC
2 18000 MFD 75 VDC surge 95 VDC
3 25000 MFD 50 VDC surge 75 VDC

Any help would be good.

Thank you

[Al_The_Man]

For 2.5% ripple at that voltage (~46vdc) and 21amp current you would require a 53,000µfd
25,000µfd would result in 5.5% ripple.
Al

[juxtoposed]

Sorry it is actually a 24 volt transformer. How does that change things?

[juxtoposed]

Also could I use more than one of the caps to reach that rating?

[Al_The_Man]

The new numbers at 24vac would be for 5.5% ripple = 35,000µfd at 2.5% ripple = 77,000µfd.
Al

[ViperTX]

Yes, parallel the first two capacitors....don't forget your diode bridge. If you need more capacitance you can parallel the third one.

[ESjaavik]

Originally Posted by juxtoposed Also could I use more than one of the caps to reach that rating?

When you place them in parallel you just add the capacitance. 59000uF for all of them in parallel. (I assume you mean uF, as a 25000 Mega-Farad capacitor will be quite big!)

The max voltage is determined by the lowest one (50V).