An Improved Metallized Film Capacitor Using a New Acrylate Coating Process

It is well known that very high reliability capacitors can be made from rolls of zinc
metallized polypropylene film. These capacitors are often used for AC and DC
applications from about I OOV to over 1000 volts. For high reliability AC applications
these capacitors are often encased and at least partially impregnated with a dielectric
fluid. This construction improves the capacitor performance by eliminating degradation
due to corona discharges and corrosion of the thin zinc electrode by the
surrounding atmosphere.

It is desirable to further improve the performance of zinc metallized capacitors so they
can be used at higher stress levels and at higher voltages, It is also desirable to
improve the corrosion resistance of the zinc electrode so the zinc metallized film can
be used in a dry roll without the encasing and impregnation with a dielectric fluid. This
paper will show how the zinc metal can be protected from corrosion by depositing a
very thin "teflonlike" coating on the thin zinc to prevent it from corroding in the
atmosphere. It will also show how the performance of both impregnated and dry
capacitors can be improved by coating the metallized film with a thin acrylate coating.