On Wed, 29 Jun 2022 08:23:22 -0400, legg <legg@nospam.magma.ca> wrote:>On Tue, 28 Jun 2022 13:37:59 -0700 (PDT), Phil Allison ><pallison49@gmail.com> wrote: > >>legg wrote: >>================ >> >>** Learn to trim - asshole. >> >>> >>> >Anybody measured the ripple? >>> >>> Electrolytic life is rms current dependent, among other things (like >>> temperature). > >If you stick one next to a vacuum tube, it's received radiated that >dominates part temperature, and voltage stress of the app that >dominates. >> >>** You just made that mad crap up. > >If you've ever calculated mtbf under Mil Hdbk 217, or Belcore, >you'd be aware of dominating life factors.Belcore has no derating factor for bad design. That often dominates MTBF.>> >>Temp is the single determining factor on expected life. >>Almost always the local ambient completely dominates. > >Current forces self-rise due the part's ESR and limited >body surface area, (unless you stick it next to a hot radiator). >The actual relevant temperature is measured on the component's >body.We are designing a fancy switching power supply and need a 20 uF cap that can handle several amps RMS, a 250 KHz triangle from a half-bridge and an inductor. We are thinking about using four 4.7 uF radial-leaded film caps in parallel. We have samples of several types on order. I plan to set up a test rig and push amps of triangle into them and see how hot they get. May as well snoop the waveform across each cap while I do that. Film cap data sheets are typically not much help. They might spec a few sinewave loss tangents and maybe allowable voltage vs frequency, but rarely spec ESR or ESL or any thermals. We have to measure all that.
Inverters vs wallwarts
Started by ●June 24, 2022
Reply by ●June 29, 20222022-06-29
Reply by ●June 29, 20222022-06-29
On Wednesday, June 29, 2022 at 10:20:07 AM UTC-4, jla...@highlandsniptechnology.com wrote:> On Wed, 29 Jun 2022 08:23:22 -0400, legg <le...@nospam.magma.ca> wrote: > > >On Tue, 28 Jun 2022 13:37:59 -0700 (PDT), Phil Allison > ><palli...@gmail.com> wrote: > > > >>legg wrote: > >>================ > >> > >>** Learn to trim - asshole. > >> > >>> > >>> >Anybody measured the ripple? > >>> > >>> Electrolytic life is rms current dependent, among other things (like > >>> temperature). > > > >If you stick one next to a vacuum tube, it's received radiated that > >dominates part temperature, and voltage stress of the app that > >dominates. > >> > >>** You just made that mad crap up. > > > >If you've ever calculated mtbf under Mil Hdbk 217, or Belcore, > >you'd be aware of dominating life factors. > Belcore has no derating factor for bad design. That often dominates > MTBF. > >> > >>Temp is the single determining factor on expected life. > >>Almost always the local ambient completely dominates. > > > >Current forces self-rise due the part's ESR and limited > >body surface area, (unless you stick it next to a hot radiator). > >The actual relevant temperature is measured on the component's > >body. > We are designing a fancy switching power supply and need a 20 uF cap > that can handle several amps RMS, a 250 KHz triangle from a > half-bridge and an inductor. We are thinking about using four 4.7 uF > radial-leaded film caps in parallel. > > We have samples of several types on order. I plan to set up a test rig > and push amps of triangle into them and see how hot they get. May as > well snoop the waveform across each cap while I do that. > > Film cap data sheets are typically not much help. They might spec a > few sinewave loss tangents and maybe allowable voltage vs frequency, > but rarely spec ESR or ESL or any thermals. We have to measure all > that.These people don't figure current into life expectancy, only voltage and temperature. https://www.cde.com/resources/technical-papers/filmAPPguide.pdf
Reply by ●June 29, 20222022-06-29
On Wed, 29 Jun 2022 08:18:39 -0700 (PDT), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>On Wednesday, June 29, 2022 at 10:20:07 AM UTC-4, jla...@highlandsniptechnology.com wrote: >> On Wed, 29 Jun 2022 08:23:22 -0400, legg <le...@nospam.magma.ca> wrote: >> >> >On Tue, 28 Jun 2022 13:37:59 -0700 (PDT), Phil Allison >> ><palli...@gmail.com> wrote: >> > >> >>legg wrote: >> >>================ >> >> >> >>** Learn to trim - asshole. >> >> >> >>> >> >>> >Anybody measured the ripple? >> >>> >> >>> Electrolytic life is rms current dependent, among other things (like >> >>> temperature). >> > >> >If you stick one next to a vacuum tube, it's received radiated that >> >dominates part temperature, and voltage stress of the app that >> >dominates. >> >> >> >>** You just made that mad crap up. >> > >> >If you've ever calculated mtbf under Mil Hdbk 217, or Belcore, >> >you'd be aware of dominating life factors. >> Belcore has no derating factor for bad design. That often dominates >> MTBF. >> >> >> >>Temp is the single determining factor on expected life. >> >>Almost always the local ambient completely dominates. >> > >> >Current forces self-rise due the part's ESR and limited >> >body surface area, (unless you stick it next to a hot radiator). >> >The actual relevant temperature is measured on the component's >> >body. >> We are designing a fancy switching power supply and need a 20 uF cap >> that can handle several amps RMS, a 250 KHz triangle from a >> half-bridge and an inductor. We are thinking about using four 4.7 uF >> radial-leaded film caps in parallel. >> >> We have samples of several types on order. I plan to set up a test rig >> and push amps of triangle into them and see how hot they get. May as >> well snoop the waveform across each cap while I do that. >> >> Film cap data sheets are typically not much help. They might spec a >> few sinewave loss tangents and maybe allowable voltage vs frequency, >> but rarely spec ESR or ESL or any thermals. We have to measure all >> that. > >These people don't figure current into life expectancy, only voltage and temperature. >https://www.cde.com/resources/technical-papers/filmAPPguide.pdfThat's interesting but, typically, qualitative and theoretical. I'll have to test actual caps. We will have a lot of air flow too, which will increase allowable RMS current and needs to be quantified too. We should orient and space the caps to take advantage of the air cooling. This ain't simple. It's distressing, in electronics data sheets and literature, how seldom you find actual numbers. I recently bought a book about electronic cooling, but it's packed with equations and theory, with not a single worked-out case of blowing air over a flat plate. There is an equation, but it's a nightmare. If I had a 6" square of 0.062 thick aluminum, and blasted 200 f/m of air along both sides, what would theta be? I'll have to measure that. And what would the temp rise be of my 4.7u film caps, in degc/watt, in still air and with air flow? Gotta measure that too.
Reply by ●June 29, 20222022-06-29
On Tuesday, June 28, 2022 at 1:38:06 PM UTC-7, palli...@gmail.com wrote:> legg wrote: > ================ > > ** Learn to trim - asshole. > > > > >Anybody measured the ripple? > > > > Electrolytic life is rms current dependent, among other things (like > > temperature). > ** You just made that mad crap up. > > Temp is the single determining factor on expected life. > Almost always the local ambient completely dominates.> > Electrolytics normally have a predicted life some orders of > > magnitude shorter than most other components> ** Then in practice often outlast the lot. > The one exception being vacuum tubes.Electrolytic capacitors are active-chemistry devices; temperature affects the seals that hold the reagents in place, and either internal heat or ambient temperature will cause aging, irrespective of electrical stress. High ripple voltage is associated with processes that cause i nternal foils to become fractured. Vacuum tubes are also active-chemistry devices; usually become gassy due to slow diffusion of contaminants. There's better chemcal integrity available in solid state devices as far as aging is concerned. Batteries exemplify the worst chemical integrity in the business... you always want to check the dates on those!
Reply by ●June 29, 20222022-06-29
jlarkin@highlandsniptechnology.com wrote:> On Wed, 29 Jun 2022 08:18:39 -0700 (PDT), Fred Bloggs > <bloggs.fredbloggs.fred@gmail.com> wrote: > >> On Wednesday, June 29, 2022 at 10:20:07 AM UTC-4, jla...@highlandsniptechnology.com wrote: >>> On Wed, 29 Jun 2022 08:23:22 -0400, legg <le...@nospam.magma.ca> wrote: >>> >>>> On Tue, 28 Jun 2022 13:37:59 -0700 (PDT), Phil Allison >>>> <palli...@gmail.com> wrote: >>>> >>>>> legg wrote: >>>>> ================ >>>>> >>>>> ** Learn to trim - asshole. >>>>> >>>>>> >>>>>>> Anybody measured the ripple? >>>>>> >>>>>> Electrolytic life is rms current dependent, among other things (like >>>>>> temperature). >>>> >>>> If you stick one next to a vacuum tube, it's received radiated that >>>> dominates part temperature, and voltage stress of the app that >>>> dominates. >>>>> >>>>> ** You just made that mad crap up. >>>> >>>> If you've ever calculated mtbf under Mil Hdbk 217, or Belcore, >>>> you'd be aware of dominating life factors. >>> Belcore has no derating factor for bad design. That often dominates >>> MTBF. >>>>> >>>>> Temp is the single determining factor on expected life. >>>>> Almost always the local ambient completely dominates. >>>> >>>> Current forces self-rise due the part's ESR and limited >>>> body surface area, (unless you stick it next to a hot radiator). >>>> The actual relevant temperature is measured on the component's >>>> body. >>> We are designing a fancy switching power supply and need a 20 uF cap >>> that can handle several amps RMS, a 250 KHz triangle from a >>> half-bridge and an inductor. We are thinking about using four 4.7 uF >>> radial-leaded film caps in parallel. >>> >>> We have samples of several types on order. I plan to set up a test rig >>> and push amps of triangle into them and see how hot they get. May as >>> well snoop the waveform across each cap while I do that. >>> >>> Film cap data sheets are typically not much help. They might spec a >>> few sinewave loss tangents and maybe allowable voltage vs frequency, >>> but rarely spec ESR or ESL or any thermals. We have to measure all >>> that. >> >> These people don't figure current into life expectancy, only voltage and temperature. >> https://www.cde.com/resources/technical-papers/filmAPPguide.pdf > > That's interesting but, typically, qualitative and theoretical. I'll > have to test actual caps. > > We will have a lot of air flow too, which will increase allowable RMS > current and needs to be quantified too. We should orient and space the > caps to take advantage of the air cooling. This ain't simple. > > It's distressing, in electronics data sheets and literature, how > seldom you find actual numbers. I recently bought a book about > electronic cooling, but it's packed with equations and theory, with > not a single worked-out case of blowing air over a flat plate. There > is an equation, but it's a nightmare. > > If I had a 6" square of 0.062 thick aluminum, and blasted 200 f/m of > air along both sides, what would theta be? I'll have to measure that. > > And what would the temp rise be of my 4.7u film caps, in degc/watt, in > still air and with air flow? Gotta measure that too. >Even in an inviscid, incompressible fluid, the equations aren't all that simple. Forced-air cooling of macroscopic systems runs at some huge and highly variable Reynolds number, depending on where you are. There was a bit of a fad in the '90s for people to publish various semi-empirical papers on fan cooling, but that sort of died out. You can compute the thermodynamic limit, obviously, because you know the inlet temperature, the air mass, the maximum component temperature, and the heat dissipated, but most heat sink systems don't get anywhere near it. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●June 29, 20222022-06-29
On Wed, 29 Jun 2022 07:19:46 -0700, jlarkin@highlandsniptechnology.com wrote:>On Wed, 29 Jun 2022 08:23:22 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Tue, 28 Jun 2022 13:37:59 -0700 (PDT), Phil Allison >><pallison49@gmail.com> wrote: >> >>>legg wrote: >>>================ >>> >>>** Learn to trim - asshole. >>> >>>> >>>> >Anybody measured the ripple? >>>> >>>> Electrolytic life is rms current dependent, among other things (like >>>> temperature). >> >>If you stick one next to a vacuum tube, it's received radiated that >>dominates part temperature, and voltage stress of the app that >>dominates. >>> >>>** You just made that mad crap up. >> >>If you've ever calculated mtbf under Mil Hdbk 217, or Belcore, >>you'd be aware of dominating life factors. > >Belcore has no derating factor for bad design. That often dominates >MTBF.The stress factors for measured voltage current and temperature are a fair indication of design integrity. Designs can be 'bad' for other reasons entirely.> > >>> >>>Temp is the single determining factor on expected life. >>>Almost always the local ambient completely dominates. >> >>Current forces self-rise due the part's ESR and limited >>body surface area, (unless you stick it next to a hot radiator). >>The actual relevant temperature is measured on the component's >>body. > >We are designing a fancy switching power supply and need a 20 uF cap >that can handle several amps RMS, a 250 KHz triangle from a >half-bridge and an inductor. We are thinking about using four 4.7 uF >radial-leaded film caps in parallel. > >We have samples of several types on order. I plan to set up a test rig >and push amps of triangle into them and see how hot they get. May as >well snoop the waveform across each cap while I do that. > >Film cap data sheets are typically not much help. They might spec a >few sinewave loss tangents and maybe allowable voltage vs frequency, >but rarely spec ESR or ESL or any thermals. We have to measure all >that.It's always been difficult determining film cap ratings. The dielectric losses usually have a positive temp co above 50C and the parts themselves can have some of the lowest part body temperature limits in the deck. Part construction and materials quality, though largely the product of automation, can vary. Not many other parts are dependent on a coat of paint for env integrity. Keep in mind that self-healing construction can mask a considerable defect level. You've probably pulled simple film decoupling caps out who's capacitance measured almost nothing compared to their original mfred values, due to repeated intervening self-healing processes. Philips published good information on polycarbonate, polyester and polypropylene parts, when they were still in the business of using them. Check their 'Components and Materials Part 15' prior to 1990. I don't think there's been much improvement on that. Siemens tended to be more spotty. CDE did some mil stuff that must have been backed up by something more than body temperature rise. Polycarbonate development has lost some steam due to issues with flammability. There were film caps in most early fluorescent bulb replacements, besides the usual HV electrolytic. At that temperature, it was a toss-up which failed first. Pulse-rated products get more attention to their reliability and ratings. If your part doesn't provide sufficient data, chances are it's a misapplication waiting to happen. Pulse steepness dV/dT (~peak current) is dependent on both the process characteristic voltage AND the part body size, so that the amps/uF can actually reduce with an increase in leadspacing. PPK and polyphenylene sulphide are potential rivals in some applications, with slightly higher temperature limits, but I don't recall anyone providing tabular or graphical data. Can't imagine where my notes could be on that stuff. Today, even the binder labels are illegible. Probably need a different kind of 'specs'. RL
Reply by ●June 29, 20222022-06-29
Anyways, wade through it and you may come up with something like this: http://ve3ute.ca/query/Polycarbonate_Current_100KHz_Philips.pdf It will be different for each dielectric, frequency of operation, temperature etc. RL
Reply by ●June 29, 20222022-06-29
On 30/6/22 05:38, Phil Hobbs wrote:> Even in an inviscid, incompressible fluid, the equations aren't all that > simple. Forced-air cooling of macroscopic systems runs at some huge and > highly variable Reynolds number, depending on where you are.Pretty sure that Reynolds number cannot be defined for an inviscid liquid. But yeah, turbulent flows are difficult however you look at them.
Reply by ●June 29, 20222022-06-29
On Wed, 29 Jun 2022 18:14:22 -0400, legg <legg@nospam.magma.ca> wrote:>Anyways, wade through it and you may come up with >something like this: > >http://ve3ute.ca/query/Polycarbonate_Current_100KHz_Philips.pdf > >It will be different for each dielectric, frequency of operation, >temperature etc. > >RLGosh, real numbers. Thanks. I just got this. It's a high voltage half-bridge test board for frying inductors and film caps. People were doing another proto board so I hung this on the end as a v-score breakaway. https://www.dropbox.com/s/2x8z6yn29ab57xf/Z524_Wing_1.jpg?raw=1
Reply by ●June 30, 20222022-06-30
Clifford Heath wrote:> On 30/6/22 05:38, Phil Hobbs wrote: >> Even in an inviscid, incompressible fluid, the equations aren't all >> that simple. Forced-air cooling of macroscopic systems runs at some >> huge and highly variable Reynolds number, depending on where you are. > > Pretty sure that Reynolds number cannot be defined for an inviscid > liquid. But yeah, turbulent flows are difficult however you look at them.My point exactly. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
