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Re: Rolled PE Caps

Hi Kevin,

>Original Poster: "Kevin Wahila" <knw2-at-lehigh.edu>
>
>What would be the difference if you used aluminum foil rather than
>aluminum flashing as the plates in a rolled poly cap?  It would just
>be so much easier to roll.  Would it perform as well though?

In terms of capacitance: No difference.
In terms of holding up to the discharge current: No difference.

I myself have sucessfully used kitchen foil in PE caps (while they
lasted...;o)), because Al flashing is a rip-off in Europe. A 10m^2
roll of 0.2mm (~0.010") costs around $60. It IS 99.9% pure
aluminum, but who needs this in a cap (esp. with THAT price
tag attached)?

Disadvantages in using AL foil instead of flashing:
--------------------------------------------------------------
1.) It creases very easily: > trapped air >partial discharges >cap death

2.) You canīt use the foil as a connector. It is way too fragile. This
      means you need some solid way to connect the plate to the
      connection terminal (like using straps and screws to attach
      the connector to the actual cap plate.

3.) Foil is ultra thin. It is nearly impossible to "round" the cut
     edges. This, too can encourage corona production.

Advantages:
----------------
1.) Cheaper.

2.) Can be easily cut with scissors or paper cutters.

3.) Lighter, flashing is heavy.

4.) As it folds easier, the possibility of the edges "digging" into the
     PE are almost non-existant. You can ruin a PE cap instantly,
     using flashing, if the sharp (and stiff) edges dig into the PE
     (effectively reducing the dielectrical thickness in a place where
     you would rather have more than less thickness, because of
     the high E-field present at this point)

All in all, I think it is a matter of personal taste. On the other hand
I donīt like rolled PE caps anymore (:o)).

"Justin Hennigan" <justinh-at-interlaced-dot-net> asked:
"And what about copper flashing?  it's a better conductor."

While this IS true, it isnīt really necessary in cap. Copper
flashing is much, much more expensive. Even commercial
caps are built with aluminum.

Coiler greets from germany,
Reinhard