[morzh]

Putting together number of caps of the same value:

Serializing of N capacitors:
- Divides the capacitance by N.
- Multiplies the WV by N.
Example: 3 caps of 1uF 500V in series will result in 0.33uF 1500V.

Paralleling of N capacitors:
- Leaves the WV the same.
- Multiplies the capacitance by N.
Example: 3 caps of 1uF 500V in parallel will result in 3uF 500V.


Now. When serializing, ESPECIALLY electrolytics (which are nown for their higher than the rest's leakage current) the equalizing resistors need to be used.
Each capacitor receives a resistor across it that should conduct the current that is about an order of magnitude higher than the leakage current.
If not put in places, the voltages across the capacitors may differ significantly, and if close enough to WV, one of the caps could receive the voltage across it that exceeds the WV.
Example: serializing 2x22uF 500V electrolytics.

A theoretical leakage acrdoss such a cap using the formula I=0.01*C*V is 100uA at 500V.
So we want the resistors that would result in 1mA of current.
This would be 500K across each cap. The power dissipated woul be 0.5W which is a bit excessive, so we could go higher in resistance, considering a healthy cap has much lower leakage.
Let's have 300uA.
The resistance is 1.7M.
The dissipation is 0.15W.

So, each capacitor of 22uF will receive a 1.7M resistor across it.

PS. Non-electrolytic caps have very low leakage and we do not have to worry about it.