I have attached a wind generator converted from a car alternator to an engine.
The generator puts out a pulse DC. How do you calculate the microfarad rating
for a DC smoothing capacitor?

Thank you for your time to read my post

 

Connect a 12V lead-acid (sealed or not) battery across it and be done with it. Regulate the battery voltage the same way they do with car alternators: modulate the field current. The battery is equivalent to a several hundred to several thousand Farad capacitor...

 

Two questions:

1. What does the pulsed DC waveform look like?
2. What does the load look like?

Both are important for formulating an answer.

 

The DC % ripple output on a 3 phase alternator is <5%.
Max.

 

So is the plan to convert 3 Phase AC to DC or something else? It is not clear what you are trying to do. A schematic would really help.