Film capacitor as power-supply filter

[George Herold]

On Saturday, October 19, 2019 at 9:29:31 PM UTC-4, Phil Allison wrote:

George Herold wrote:
--------------------

Some retard posted:

Why measure past the rated voltage? You are never going to operate there.
You simply risk damaging the capacitor for no good reason.


I just want to say, that when people tell me *not* to measure
parts above and beyond the specs.. The more I want too. :^)


** Test 'em to destruction I say ...

Just kidding, but current limited breakdown testing is simply the only way to do find out the actual limit of many parts. Carried out sensibly, it does no damage.

Anecdote:

I once purchased a quantity of MJ15030/31s from a popular components retailer in Sydney. These are medium power TO220 pak devices rated at 160V for use as output drivers in power amplifiers.

Nearly all of them were *dead short* as purchased !!

I got a very grumpy reaction when I returned them and refused to take more from the same bin. WTF - Motorola do not supply dead BJTs.

I smelt a rat, someone had been at them before me.

Turned out a local amplifier maker ( Chris from PTM Electronics ) "borrowed" hundreds of them from the same store to put through his quality checking process then returned any he did not like.

His "process" involved the use of an old HP Curve Tracer, which is well capable of destroying such devices and had done so to a great many.

Wot an asshole.


..... Phil

Huh, I mostly buy from digikey, (newark/mouser/..)
I got some crap 79l12 (to-93 pack) voltage regs
from jameco ~20 years ago, and never more.

Good vendors and good customers, both should be
cherished.

George h.

 

[Bill Sloman]

On Sunday, October 20, 2019 at 1:42:51 AM UTC+11, jla...@highlandsniptechnology.com wrote:

On Sat, 19 Oct 2019 03:37:00 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Steve Lunatic Wilson wrote:

----------------------------


Why measure past the rated voltage? You are never going to operate there.
You simply risk damaging the capacitor for no good reason.

The curve shown in fig. 4 is a generic curve. The actual curves are
different for each capacitor, and depend on variables such as those
described above. So it is impossible to represent all capacitors at once.

You need to also try measuring the capacitor voltage with a constant
current source. That could give valuable new information.

** This fuckwit troll is a pernicious false arguer and incorrigible context shifter.

He is delusional to the extent he literally believes his own bullshit.

Prefect candidate for the "Church of Scientology" don't you think ?


He argues out of emotion rather than reason. I have several anti-fans
here who are dying to show me wrong, and will commit any bogus mental
contortion in that cause.

As if John Larkin doesn't.

This is amusing, because I'm really interested in how people reason
toward truth, and especially how they don't.

But is unwilling to study his own behaviour in that context.

Any train of thought that suggest that John Larkin is less than perfect gets ruthlessly repressed.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Sunday, October 20, 2019 at 10:20:34 AM UTC+11, jla...@highlandsniptechnology.com wrote:

On Sat, 19 Oct 2019 15:23:03 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

jla...@highlandsniptechnology.com wrote:

<snip>

This is amusing, because I'm really interested in how people reason
toward truth, and especially how they don't.

** Same interest here - the sheer, bloody irrationality of most people is STAGGERING !

The fact was driven home to me forcefully soon as I began posting on usenet, about 20 years ago. People make up their minds about something in a flash, using great gobs of false logic plus "intuition" - then will not back down at any price.

That so many seemingly bright people go right through college and university WITHOUT learning clear thinking or how to spot and avoid logical fallacies is a crime.

I could go on and on ...

Let's be careful here; we are in dire danger of agreeing on something.

Sadly, the prize example around here got a university education - admittedly at Tulane - and posts denialist propaganda about anthropogenic global warming whenever he posts on the subject.

This displays a massive failure in critical thinking. His vanity prevents him from recognising this, and commits him to total faith in every last silly idea that Anthony Watts puts on his web-site.

https://www.sourcewatch.org/index.php?title=Anthony_Watts

--
Bill Sloman, Sydney

 

On Sat, 19 Oct 2019 18:29:26 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

George Herold wrote:
--------------------

Some retard posted:

Why measure past the rated voltage? You are never going to operate there.
You simply risk damaging the capacitor for no good reason.


I just want to say, that when people tell me *not* to measure
parts above and beyond the specs.. The more I want too. :^)


** Test 'em to destruction I say ...

Just kidding, but current limited breakdown testing is simply the only way to do find out the actual limit of many parts. Carried out sensibly, it does no damage.

Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is
failure.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?dl=0

https://www.dropbox.com/s/gpc169hj1ilp6xa/photo01x_exploded_resistors.jpg?dl=0



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Allison]

jla...@highlandsniptechnology.com wrote:

-----------------------------------------

** Test 'em to destruction I say ...

Just kidding, but current limited breakdown testing is simply the only way to do find out the actual limit of many parts. Carried out sensibly, it does no damage.


Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is
failure.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?dl=0

https://www.dropbox.com/s/gpc169hj1ilp6xa/photo01x_exploded_resistors.jpg?dl=0

** I have a TO3 lateral MOSFET with a neat, round hole in the top of the lid.

Not the only example I have seen.

Just below the hole is the top of the drain pin, somewhat burnt.




...... Phil

 

[Phil Allison]

George Herold wrote:

---------------------

Anecdote:

I once purchased a quantity of MJ15030/31s from a popular components retailer in Sydney. These are medium power TO220 pak devices rated at 160V for use as output drivers in power amplifiers.

Nearly all of them were *dead short* as purchased !!

I got a very grumpy reaction when I returned them and refused to take more from the same bin. WTF - Motorola do not supply dead BJTs.

I smelt a rat, someone had been at them before me.

Turned out a local amplifier maker ( Chris from PTM Electronics ) "borrowed" hundreds of them from the same store to put through his quality checking process then returned any he did not like.

His "process" involved the use of an old HP Curve Tracer, which is well capable of destroying such devices and had done so to a great many.

Wot an asshole.


Huh, I mostly buy from digikey, (newark/mouser/..)

** This was quite a while ago, about 1985.

Companies like Farnell / Newark etc had not set up business in Australia then and getting trustworthy semis in small quantities was a regular hassle.

Besides the damaged MJs, I got any number of Motorola fakes from well known outlets about that same time - mostly MJ15003/4 types from Dick Smith Electronics, remember the Aussie helicopter aviator ?

I always got my money back and then did my level best to expose the scumbags who were still openly selling them.

I received nasty lawyers letters and criminal threats for doing this on a local electronics forum.



...... Phil

 

[Phil Allison]

Piotr Wyderski wrote:

-------------------

mc@uga.edu wrote:

Is there any reason not to use a 20-uF 900-volt film capacitor
as a power supply filter?


Except for its price, no.

** Even that is NOT an issue.

Compared to two, good quality, long life electros.


https://au.mouser.com/ProductDetail/KEMET/C4AQCBW5200A3FJ?qs=sGAEpiMZZMv1cc3ydrPrF95ZAHiPXMKgQ3r3TgzZkS816veTKZI9aw%3D%3D

https://www.partsconnexion.com/ATOM-76291.html


** $7 versus $36.



..... Phil

 

[Piotr Wyderski]

mc@uga.edu wrote:
> Is there any reason not to use a 20-uF 900-volt film capacitor as a power supply filter?

Except for its price, no. I use 50uF/900V for the same purpose. But then
it pays off to go to a much higher bus voltage with your PFC unit --
stored energy is roportional to V^2. The data sheet says that at 600
its useful life is expected to be 1e6 hours.

Best regards, Piotr

 

[Steve Wilson]

jlarkin@highlandsniptechnology.com wrote:

> Unless a part is very expensive, may as well test it to destruction.

Be careful doing that with electrolytics. The process of generating Al2O3
gives off hydrogen gas:

2Al + 3H2O --> Al2O3 + 3H2 (Gas) + 3e

At high rates this can exceed the capacity of the capacitor to reabsorb and
the hydrogen is released outside the capacitor. If the cap is in an enclosed
space, a dangerous buildup of hydrogen gas can provide the basis for an
explosion.

A second problem is high current can cause heating which can boil the water
in the electrolyte. The buildup of steam can rupture the case and result in
an explosion.

I had the unfortunate experience of an electrolytic explosion once. The cap
was failing but I didn't know about it since the unit was in its case. When
the cap blew, it left a dent in the 1/16 inch lid that clearly outlined the
top of the capacitor. The inside of the unit was a mess of electrolyte and
shredded aluminum foil. This was in the old days when the electrolyte was
liquid and would slosh around when shaken. But don't underestimate the power
of a steam explosion, and beware of caps that start to get hot.

 

[Piotr Wyderski]

Bill Sloman wrote:

> IIRR Mathcad and Scicad can do it too.

Why not Octave (free) or Matlab (better)? It can plot, it can solve
differential equations, it can compute FFT...

It is may favourite program for magnetics design if FEM-level modelling
is not needed.

Best regards, Piotr

 

[Piotr Wyderski]

Phil Allison wrote:

> Film caps have plenty of overvoltage capacity

Capacity is one thing, its guaranteed specification is another. For
example, those:

https://www.vishay.com/docs/26015/mkp1848cdclink.pdf

can withstand 1.5V_NOM for 10s. This is his 150% stress. One can safely
design for this overvoltage, not just rely on some built-in safety
margin. If 900V nominal weren't enough, OTOH...

Best regards, Piotr

 

[Phil Allison]

Steve Wilson wrote:

------------------------

jlarkin@highlandsniptechnology.com wrote:

Unless a part is very expensive, may as well test it to destruction.

** JL has no empathy for small components.

Few EEs do.

Be careful doing that with electrolytics. The process of generating Al2O3
gives off hydrogen gas:

2Al + 3H2O --> Al2O3 + 3H2 (Gas) + 3e

At high rates this can exceed the capacity of the capacitor to reabsorb and
the hydrogen is released outside the capacitor. If the cap is in an enclosed
space, a dangerous buildup of hydrogen gas can provide the basis for an
explosion.

** Crikey....

A second problem is high current can cause heating which can boil the water
in the electrolyte. The buildup of steam can rupture the case and result in
an explosion.

** Nah - just a cloud of white, smelly mist.

I had the unfortunate experience of an electrolytic explosion once. The cap
was failing but I didn't know about it since the unit was in its case. When
the cap blew, it left a dent in the 1/16 inch lid that clearly outlined the
top of the capacitor. The inside of the unit was a mess of electrolyte and
shredded aluminum foil.

** Seen that once or twice.

This was in the old days when the electrolyte was liquid and would
slosh around when shaken.

** Huh ?? Doubt that is true.

But don't underestimate the power
of a steam explosion, and beware of caps that start to get hot.

** Of course, that is why all electros have a pressure relief mechanism.

The plus lead plug can burst out, there are break away groves in the bottom of radial types and large cans have a plugged hole on top.

FYI:

One time, despite my strong advice, a customer refused to let me re-cap his 1906s Fender tube amp saying his available funds did not allow for that.

Two weeks later, while playing on stage, one of the HV electros puked its insides outside - covering the area around his amp with a thick fog.

Folk in the audience thought it was part of the show ...

All new electros were fitted the next week, with a promise to me never to doubt my warnings again.



....... Phil

 

[Phil Allison]

Piotr Wyderski wrote:

--------------------

Phil Allison wrote:


Film caps have plenty of overvoltage capacity

** Really don't think I wrote that and it sure ain't my opinion.

I treat polys with some caution, especially in regards to AC voltage capacity.

The data sheets lie, polyester and polycarbonate types blow up.

Supply frequency AC kills them, due to internal corona.

High frequency AC (say 10kHz ) sets polyester types on fire.

You can make a 100nF Green Cap smoke and explode with a 40W bench amplifier and a series inductor of a few mH operating at resonance.

Good cheap fun.



..... Phil

 

[Piotr Wyderski]

Phil Allison wrote:

** Even that is NOT an issue.

Compared to two, good quality, long life electros.

I agree, same conclusion on my end. Other parameters are stellar as well.

Best regards, Piotr

 

[Cursitor Doom]

On Sat, 19 Oct 2019 20:10:27 -0700, jlarkin wrote:

Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is failure.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?dl=0

https://www.dropbox.com/s/gpc169hj1ilp6xa/
photo01x_exploded_resistors.jpg?dl=0

Nowadays you're supposed to warn people before showing distressing images
like those, given the number of snowflakes there are these days.

If you've been emotionally affected by clicking on the above links, you
can find support here: http://www.im-in-crisis.org/

There. That's the proper way.


--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Phil Allison]

Cursitor Doom wrote:

--------------------

jlarkin wrote:


Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is failure.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?dl=0

https://www.dropbox.com/s/gpc169hj1ilp6xa/
photo01x_exploded_resistors.jpg?dl=0

----------------------------------

Nowadays you're supposed to warn people before showing distressing images
like those, given the number of snowflakes there are these days.

** OK - that's cute & funny.

If you've been emotionally affected by clicking on the above links, you
can find support here: http://www.im-in-crisis.org/

** But that's not a bit funny.




..... Phil

 

On Sun, 20 Oct 2019 07:44:01 -0000 (UTC), Steve Wilson <no@spam.com>
wrote:

jlarkin@highlandsniptechnology.com wrote:

Unless a part is very expensive, may as well test it to destruction.

Be careful doing that with electrolytics. The process of generating Al2O3
gives off hydrogen gas:

2Al + 3H2O --> Al2O3 + 3H2 (Gas) + 3e

At high rates this can exceed the capacity of the capacitor to reabsorb and
the hydrogen is released outside the capacitor. If the cap is in an enclosed
space, a dangerous buildup of hydrogen gas can provide the basis for an
explosion.

Conservation of energy says that the explosion won't liberate more
joules than I pushed into the cap. None of my bench supplies can
deliver explosive amounts of energy in any reasonable time.

My cap test used a wonderful old HP 6212A power supply with the
current limit set to maybe 10 mA. The cap never got warm.

https://www.dropbox.com/s/arbdkg6gocbpd66/HP6212A.JPG?raw=1

I never worry about stuff like that. So far so good.




--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Sun, 20 Oct 2019 11:04:51 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 19 Oct 2019 20:10:27 -0700, jlarkin wrote:

Unless a part is very expensive, may as well test it to destruction.

With some parts, the first indication of impending breakdown is failure.

https://www.dropbox.com/s/4nxm7m2q3j3buvc/ExFets.jpg?dl=0

https://www.dropbox.com/s/gpc169hj1ilp6xa/
photo01x_exploded_resistors.jpg?dl=0

That resistor pic is actually by Win, but he used my exploder machine.

Nowadays you're supposed to warn people before showing distressing images
like those, given the number of snowflakes there are these days.

If you've been emotionally affected by clicking on the above links, you
can find support here: http://www.im-in-crisis.org/

Linked to from Im-a-sad-wuss.myomy

There. That's the proper way.

Have a good cry and move on.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Cursitor Doom]

On Sun, 20 Oct 2019 08:13:17 -0700, jlarkin wrote:

Conservation of energy says that the explosion won't liberate more
joules than I pushed into the cap. None of my bench supplies can deliver
explosive amounts of energy in any reasonable time.

Then just use a car battery. Or better yet a 24V truck battery. :->



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

On Sun, 20 Oct 2019 11:03:56 -0700 (PDT), tabbypurr@gmail.com wrote:

On Saturday, 19 October 2019 15:42:51 UTC+1, jla...@highlandsniptechnology.com wrote:
On Sat, 19 Oct 2019 03:37:00 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

Steve Lunatic Wilson wrote:

----------------------------


Why measure past the rated voltage? You are never going to operate there.
You simply risk damaging the capacitor for no good reason.

The curve shown in fig. 4 is a generic curve. The actual curves are
different for each capacitor, and depend on variables such as those
described above. So it is impossible to represent all capacitors at once.

You need to also try measuring the capacitor voltage with a constant
current source. That could give valuable new information.



** This fuckwit troll is a pernicious false arguer and incorrigible context shifter.

He is delusional to the extent he literally believes his own bullshit.

Prefect candidate for the "Church of Scientology" don't you think ?

If he ain't one already that is ...



He argues out of emotion rather than reason. I have several anti-fans
here who are dying to show me wrong, and will commit any bogus mental
contortion in that cause.

This is amusing, because I'm really interested in how people reason
toward truth, and especially how they don't.

IME some people seek truth, some want nothing to do with it. The latter are childish time wasters.


NT

Truth, in this newsgroup, is designing electronic circuits that work.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics