Low dissipation factor capacitors

Try Wima

Loads of people make polypropylene caps. From experience Epcos has possibly the largest range.

Where does one buy 'bad' polypropylene from btw ?

Graham

Thanks, my boss was worried there would be no other supplier.

George

Excellent! The big ones must be expensive.

Hmmm, I don't know. I suposse I could try rolling you some bad ones, they'd cost though.

Thanks George

They have an astonishing range, both metallised film-foil and film-foil-film for ultimate performance. All with detailed charts showing max dV/dt or Amps vs freq etc.

Polypropylene caps are always a bit expensive. For cheaper try Samwha. They look like those green dipped mylar caps but are dipped blue ? I think and they do give some transient data. I think they designed them for TV sets.

Graham

Vishay-BC (ex Philips passives) probably still do some too. The Philips range used to include lovely 1% tolerance smaller value ones. Brilliant for filters. Also in giveawy blue. That range was only radial though and didn't go to high values.

Graham

Not to forget the British ! LCR are still making them.

AND polycarbonate and polystyrene ! Must be about the last people in the world doing that !

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

In the UK we have these sweets called Tooty Frooty's.... If you have a taste for these things (I have), and you're hungry for them while working in range of a box of these mylar caps, be afraid, be very afraid... >:) It takes self control not to want to try a nibble.

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Big yellow ones with 40µF and 900 or more volts? Got to ask because I wanted something like that or stronger for a laser flash driver once and I never found anything that big via Google searches.

LMAO !

Graham

The Epcos polypropylenes are all AFAIK in blue plastic boxes. Blue seems to be the typical colour for polypropylene.

What was the PRR on your laser ?

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Lots of yellow axial cylindrical ones exist for HV, and I've seen them in passive speaker crossovers too.

Slow. Just needed a fast pulse, shaped by a coil. It had a fat yellow polypropylene cap, and some people reported using more oomph so I looked around to see if suitable caps existed. Couldn't find any nig enough until I saw the big polyethylene caps that some people in Russia were selling on eBay. Expensive, and slow to ship, and massively overpowered for a small rangefinder YAG.

Those sound more like polyester to me. No need ever for polypropylenes in an audio crossover. Can you give me some series numbers ?

How slow ?

Photograhic high power flash units simply use purpose designed electrolytics designed for ultra-fast discharge. About 1000uF @ 320V !

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Want to bet? Can't give you numbers but Google image results alone throw them out ten at a time in various contexts, especially in audio. (Most times I see polyesters, they're in mains filters or cheap timing circuits for small signals).

Not the same. Flashlamps for small YAG laser pumping can work, sort of, with photoflash, people do that, but it's not good design, it doesn't give the well-controlled pulse needed, and that's done with a polypropylene (or polyethylene) cap and a pulse shaping coil.

Doing polystyrene caps ? Well, Mouser sell cheap ones under their "Xicon" house brand. Their published C vs. temp curves don't look as good as the figures on LCR's data sheets, though.

Polystyrene caps are as rare as hen's teeth now. LCR say the film is no longer made but they've got stock for something like 15 yrs production at current rates.

Graham

"include lovely 1% tolerance smaller value ones. Brilliant for filters. "

Wonderful! I've been using 2% tolerance caps from Panasonic and had ordered some of their new 1% ones for a new filter design. I was looking forward ~1% 'out of the box' performance.

George