Calculating Filter Capacitance

[CapnC]

I've seen this equation posted several times C~(80000*I)/Vdc.

Were was it derived from? I was looking through my electronics devices book and I was trying to work backwards starting with the ripple factor equation - eq: r=Vr/Vdc(100)

Vr = rms ripple voltage
Vdc = filtered dc output voltage

I was working backwards with 2.5 % ripple and 5 % ripple (What is a common % ripple to use?)

following
eq: Vr = [0.0024(Vdc)]/(Rl)(C)

Rl = Load Resistance
C = Capacitance of Filter capcitor

You see, I am finding it hard to work backwards not knowing what Vdc is or Vr.

Any suggestions??

I'm looking at putting these two toroid transformers in parallel...

EBAY:
You are bidding on 2 new 800VA toroidal transformers. They are precisely made for high-end power amp or servo amp. They have very low power loss and magnetic leak. Labeled input 115 / 230 VAC 50/60 Hz (single coil with center tap) and outputs 40VAC x 2 (dual coils) and 15V x 2(Dual coils).
1. Primary I = 0.03A, Secondary V = 46.2VAC at 0.0A
2. Primary I = 1.75A, Secondary V = 45.3VAC at 4.5A
3. Primary I = 3.41A, Secondary V = 44.5VAC at 8.9A
4. Primary I = 5.02A, Secondary V = 42.9VAC at 12.9A
5. Primary I = 6.76A, Secondary V = 41.6VAC at 16.6A

I plan on hooking the two 40VAC from each transformer in parallel through one bridge rectifier and unwinding the two 15Vac to 4.5 Vac to use as 5v supply and run it through a separate bridge rectifier. I need help determining the size of the capacitor for the 40Vac (55.15 Vdc after rectification) and for the 4.5Vac (~5 Vdc after rectification)

I've gotten confused about determining the current from this figure 800VA - is it I = 800VA/Vac or 800VA/Vdc?

I think the total current would come out to ~30amps

Using this formula C=(80,000*I)/Vdc I get:

55.16Vdc : C = 43,509 uF
5Vdc: C = 480,000 uF ???? $$$$

Any suggestions...Please

[OCNC]

Originally Posted by CapnC Using this formula C=(80,000*I)/Vdc I get: 55.16Vdc : C = 43,509 uF 5Vdc: C = 480,000 uF ???? $$$$ Any suggestions...Please

Are you planning on using 30A at 5V?

Chris

[CapnC]

Originally Posted by OCNC Are you planning on using 30A at 5V? Chris

I'm using three bi-level drivers (MBL 536 Anaheim Automation). The 5v is for the low voltage supply. The 55.16v is for the high voltage supply. I have calculated I need 18.3 amps for all three drivers. I might as well build the supply to use all the 30 amps in case I need it in the future.

[Al_The_Man]

Originally Posted by CapnC I'm looking at putting these two toroid transformers in parallel... EBAY: You are bidding on 2 new 800VA toroidal transformers. They are precisely made for high-end power amp or servo amp. They have very low power loss and magnetic leak. Labeled input 115 / 230 VAC 50/60 Hz (single coil with center tap) and outputs 40VAC x 2 (dual coils) and 15V x 2(Dual coils). 1. Primary I = 0.03A, Secondary V = 46.2VAC at 0.0A 2. Primary I = 1.75A, Secondary V = 45.3VAC at 4.5A 3. Primary I = 3.41A, Secondary V = 44.5VAC at 8.9A 4. Primary I = 5.02A, Secondary V = 42.9VAC at 12.9A 5. Primary I = 6.76A, Secondary V = 41.6VAC at 16.6A I plan on hooking the two 40VAC from each transformer in parallel through one bridge rectifier and unwinding the two 15Vac to 4.5 Vac to use as 5v supply and run it through a separate bridge rectifier. I need help determining the size of the capacitor for the 40Vac (55.15 Vdc after rectification) and for the 4.5Vac (~5 Vdc after rectification) I've gotten confused about determining the current from this figure 800VA - is it I = 800VA/Vac or 800VA/Vdc? Any suggestions...Please

A couple of suggestions, if you parallel them up make sure they are both phased correctly when you hook them up, If you are removing windings from the 15v, hopefully they are on the outside (last winding) otherwise you would have to remove them all. Also the recommended calculation for VA and obtaining the total AC current is IAC=1.8*IDC.
Al

[trubleshtr]

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http://hyperphysics.phy-astr.gsu.edu...con.html#emcon

[trubleshtr]

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