[sdiy] [ot/3] Using ElectrolytCapacitors

[John L Marshall]

I agree.

There are large oil capacitors for motor starting and resonating CV
(constant voltage) transformers. These capacitors have an AC voltage rating.

Mains voltage will be about 340 volts peak-to-peak in the USA. Double that
in GB.

John

----- Original Message -----
From: harry <harrybissell at prodigy.net>
To: Timo Weggen <tweggen at cybernoia.de>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, October 06, 2001 9:56 AM
Subject: Re: [sdiy] [ot/3] Using ElectrolytCapacitors


> Hi Timo
>
> Y'gonna get yerself killed (likely)
>
> Electrolytic capacitors in an AC line could (probably) be very
dangerous...
>
> Even with the configuration you have shown (bipolar)... you will need
> resistors across the caps, you probably need to match the values, you
> would probably want to use inverse series diodes to limit reverse voltage
> on the cap that is reverse biased... and
>
> Electrolytic Caps have (relatively) poor RIPPLE CURRENT ratings... this
> is the ability to handle an AC current waveform, as opposed to the DC they
> are used to dealing with. Unless something will inherently limit the
> current to
> a value well below the ripple current rating, they will get hot and either
> live a short
> life before they blow... or just blow !!!
>
> Search for a FILM CAPACITOR (many companies make these, such as
> Cornell-Dubilier) replacement for an electrolytic cap. They are non
> polarized,
> have probably 10x the ripple current rating of the equivalent
> electrolytic... and
> you need only 1/2 the capacitance
>
> (Remember when you put the electrolytics in series... you needed twice the
> capacitance in each can)
>
> The price may be higher... size of one film is probably about the same as
> two
> e-lytics... they will weigh more.
>
> Still.. be sure to watch out for the ripple current rating.
>
> And good luck.
>
> BTW I have never been happy with the back to back electrolytics... I have
> blown them up every time.  If you want to talk offlist e-mail me direct
and
> we
> could discuss what you are trying to do...
>
> H^) hary
>
> Timo Weggen wrote:
>
> > Hello,
> >
> > first, I'm no engeneer, I don't know very much about electronics, but I
> > am eager to learn. Thus I listen what you all write here.
> > Now, in an experimental circuit, I need quite beeg (470uF) capacitors
> > in a AC line.
> > My father told me recently, he'd used successfully used ElectrolytCaps
> > like that, and it worked:
> >
> > ---[]!--![]----
> >
> > (Instead of a single hige --||--)
> >
> > But I am not sure I got it right, and I also want to understand it.
> >
> > TIA
> >
> > Timo
>
>