Re: Polyester Film Capacitors

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> 
> Hi Duncan,
> 
> Polystyrene is alive and well and is commonly available as a capacitor
> dielectric.  However, the newer films are much more popular and are getting
> designed in as just the defacto standard.  Polystyrene's dissipation factor
> is 0.07 compared to polypropylene at 0.0001  That means they would run 700
> times hotter in our favorite application ;-)  There are many high voltage
> films out there, but we need super low dissipation factors.  Such caps also
> have high dV/dT and low inductance which we love too.
> 
> Cheers,
> 
>         Terry

	Where did you get those numbers, Terry?????  According to my "Reference
Data for Radio Engineers" the dissipation factor of polystyrene at 1 MHz
is "<0.0001".  Only goes up to 0.00033 at 300 MHz!  Don't have
polyprolylene in this handbook, but believe it is similar in properties
to polyethylene.  Looked up polypropylene capacitor characteristics and
find only that the dissipation factor at 1 KHz is "<0.1%", or much
poorer than polystyrene.  Looked at a number of different manufacturers
and all list the same number.

Ed