Filter dc voltage

[ejl7007]

Hi guys, I believe I read somewhere in your forum That a 4,700uF Cap was used to filter dc voltage.  Is that a standard size?  Is that for a 12 volt mill?

Help

Cheers

[ghurd]

A 4700uF is a big cap.

What do you want it to do?

I have a feeling this is my fault.

The cap will not help with a 3-ph windmill.

The cap will not help with a generator (Ametek or brushed) windmill.

It helps with a single phase alternator, and if the bridge is on/near the tower.

I got more caps to try it in the other recommended ways.  Didn't get the time.

G-

[ejl7007]

Hi G, I am building my own dual rotor, three phase alternator.  I just read that a cap like a "smoothing Cap" would help filter the dc voltage.  I am pretty sure that it was rated @ 4,700 uF. Anyhow, I found a 2 Farad  20 V Cap in a car audio store and thought....let me connect it to the battery in parallel.  I don't know. I ran my alternator, however, and when the cap charged, the voltage increased.  What gives?  your reply was most helpful though. i.e.

 "The cap will not help with a 3-ph windmill.

The cap will not help with a generator (Ametek or brushed) windmill.

It helps with a single phase alternator, and if the bridge is on/near the tower."

Cheers G.

[ghurd]

I have a feeling you are confusing a few issues.  Mostly how these items interact.

The cap will not help a 3-ph PMA.

Be careful with a 2F cap.  They can be very dangerous.

G-

[ejl7007]

I am sorry for not being more explicit.  Anyhow, The cap is now out of the equation.

If the Cap cannot help then I don't need it.  The article I read must've been reffering to single phase, most likely. What a waste of $50.00 I suppose.  

But boy, are they Powerful!!!!!!!

Thanks G-

[ejl7007]

Hey G,  I have found an article in which a Cap is used.....Spefically a 2F Cap. It is about converting a bicycle, connecting it to a car alternator and pedaling really fast to get it going.  It is called, "Human powered TV" or something like that.  Here is the link, so you can check for yourself....

http://www.scienceshareware.com/DIY/BYO/U-gen/step4-remove-retaining-ring.htm#Step-13

I don't understand!  In that article, they use a car alternator which is supposedly 3-phase...I did read it but I'm a bit confused.  Why can we not use a Cap?

Help!!

EJL

[ghurd]

They are using the cap instead of a battery.

The cap gets charged like a battery.  Caps do not hold much useable power.

He says "it has tons of power stored in it", meaning it can melt a screw driver, but to run the 34W Harry Potter game requires constant pedaling.

Fun toy maybe, but I would use a battery.

The rectified 3-phase (meaning DC) can charge a cap, which is why your voltage increased.

Instead of the meter reading the average or RMS voltage, the capacitor stored potential until the capacitor reached peak voltage, so the meter reads nearly the peak voltage.

http://www.allaboutcircuits.com/vol_6/chpt_5/6.html

G-