Forums

X-capacitor failure modes?

Started by Joerg September 21, 2013
Folks,

This afternoon I took the old HP-4191A apart. Yesterday in the middle of
some measurements it went pop-pop-pop, loud, like firecrackers. I ran
over and turned it off, upon which the popping stopped. An immense
amount of light-gray smoke wafted out and it had an odd stench to it.
The stench lingered for hours.

I can't find any source and upon powering it up the analyzer worked
fine. That was before I changed anything. As if it had repaired itself.
The only thing I could see is a crack in the plastic of the X-capacitor.
Snipped the thing out, measured, has almost 0.28uF capacitance (27% more
than stated) and no leakage current. There is another X-cap and two
Y-caps inside a canned IEC receptacle but those can't be the culprits
because that is on the line side of the power switch.

Is it possible that an X-cap self-heals to the point where you can
barely see a thing, yet release a serious plume of smoke? It is a Rifa
GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.

-- 
Regards, Joerg

http://www.analogconsultants.com/
On 22-09-2013 00:17, Joerg wrote:
> Folks, > > > I can't find any source and upon powering it up the analyzer worked > fine. That was before I changed anything. As if it had repaired itself. > The only thing I could see is a crack in the plastic of the X-capacitor.
I've once had a fluorescent lamp which produced popping sounds for some time and also smelled a bit of burned plastics. Was hard to localize where it came from hence it took some time to find the culprit. It turned out to be an X-capacitor, which also had a crack in the housing. Had to look carefully, because besides the rather unimpressive crack, it looked just fine.
> > Is it possible that an X-cap self-heals to the point where you can > barely see a thing, yet release a serious plume of smoke? It is a Rifa
No idea. I didn't made any measurements on it, just replaced it. Thus I don't know whether it self-healed or not. Regards, Klaus
On Sat, 21 Sep 2013 15:17:34 -0700, the renowned Joerg
<invalid@invalid.invalid> wrote:

>Folks, > >This afternoon I took the old HP-4191A apart. Yesterday in the middle of >some measurements it went pop-pop-pop, loud, like firecrackers. I ran >over and turned it off, upon which the popping stopped. An immense >amount of light-gray smoke wafted out and it had an odd stench to it. >The stench lingered for hours. > >I can't find any source and upon powering it up the analyzer worked >fine. That was before I changed anything. As if it had repaired itself. >The only thing I could see is a crack in the plastic of the X-capacitor. >Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >than stated) and no leakage current. There is another X-cap and two >Y-caps inside a canned IEC receptacle but those can't be the culprits >because that is on the line side of the power switch. > >Is it possible that an X-cap self-heals to the point where you can >barely see a thing, yet release a serious plume of smoke? It is a Rifa >GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
It's possible.. the old Philips 630VDC (I think the AC rating was 250VAC on those) Polyester caps from that era were explicitly claimed to be self-healing. I don't think I ever accidentally tested it, but I would have expected less drama (but if it formed an arc track internally, then an arc might have become self-sustaining). I would have expected more leakage, but maybe it burned back. Did it smell more like burning polyester than burning transformer? If I had it, I would stick it on my "classic" Hi-pot tester and see where it breaks over. I guess you could dissect it and see what the insides look like, Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Spehro Pefhany wrote:
> On Sat, 21 Sep 2013 15:17:34 -0700, the renowned Joerg > <invalid@invalid.invalid> wrote: > >> Folks, >> >> This afternoon I took the old HP-4191A apart. Yesterday in the middle of >> some measurements it went pop-pop-pop, loud, like firecrackers. I ran >> over and turned it off, upon which the popping stopped. An immense >> amount of light-gray smoke wafted out and it had an odd stench to it. >> The stench lingered for hours. >> >> I can't find any source and upon powering it up the analyzer worked >> fine. That was before I changed anything. As if it had repaired itself. >> The only thing I could see is a crack in the plastic of the X-capacitor. >> Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >> than stated) and no leakage current. There is another X-cap and two >> Y-caps inside a canned IEC receptacle but those can't be the culprits >> because that is on the line side of the power switch. >> >> Is it possible that an X-cap self-heals to the point where you can >> barely see a thing, yet release a serious plume of smoke? It is a Rifa >> GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there. > > It's possible.. the old Philips 630VDC (I think the AC rating was > 250VAC on those) Polyester caps from that era were explicitly claimed > to be self-healing. I don't think I ever accidentally tested it, but I > would have expected less drama (but if it formed an arc track > internally, then an arc might have become self-sustaining). I would > have expected more leakage, but maybe it burned back. > > Did it smell more like burning polyester than burning transformer? >
Judging by the smell I was almost sure it was the transformer. But it's encapsulated and the only place smoke could come out is a small hole where all its wires tunnel out. But there was not smoke residue anywhere. The X-cap sits right in the open, so that is one of the very few parts that could spew stuff without leaving traces.
> If I had it, I would stick it on my "classic" Hi-pot tester and see > where it breaks over. > > I guess you could dissect it and see what the insides look like, >
Maybe I'll do that, I kept it. But first my wife wants me to barbecue chicken wings, bratwurst and peppers. And when I pulled that analyzer out of the rack she remarked "Don't put that back in before cleaning back there!". It's running for 2h now, sans problems, with a new X-cap. While I cleaned the lab bench, rack and all that. -- Regards, Joerg http://www.analogconsultants.com/
Klaus Bahner wrote:
> On 22-09-2013 00:17, Joerg wrote: >> Folks, >> >> >> I can't find any source and upon powering it up the analyzer worked >> fine. That was before I changed anything. As if it had repaired itself. >> The only thing I could see is a crack in the plastic of the X-capacitor. > > I've once had a fluorescent lamp which produced popping sounds for some > time and also smelled a bit of burned plastics. Was hard to localize > where it came from hence it took some time to find the culprit. > > It turned out to be an X-capacitor, which also had a crack in the > housing. Had to look carefully, because besides the rather unimpressive > crack, it looked just fine. >
Ah, ok, so it could indeed be the X-cap then. I was impressed how much smoke it let off. The whole room (size of a bedroom) was full of smoke. [...] -- Regards, Joerg http://www.analogconsultants.com/
On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid>
wrote:

>Folks, > >This afternoon I took the old HP-4191A apart. Yesterday in the middle of >some measurements it went pop-pop-pop, loud, like firecrackers. I ran >over and turned it off, upon which the popping stopped. An immense >amount of light-gray smoke wafted out and it had an odd stench to it. >The stench lingered for hours. > >I can't find any source and upon powering it up the analyzer worked >fine. That was before I changed anything. As if it had repaired itself. >The only thing I could see is a crack in the plastic of the X-capacitor. >Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >than stated) and no leakage current. There is another X-cap and two >Y-caps inside a canned IEC receptacle but those can't be the culprits >because that is on the line side of the power switch. > >Is it possible that an X-cap self-heals to the point where you can >barely see a thing, yet release a serious plume of smoke? It is a Rifa >GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
They are Self-Healing to the point that they don't pose a safety risk. <http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf> Cheers
On 2013-09-21, Joerg <invalid@invalid.invalid> wrote:
> I can't find any source and upon powering it up the analyzer worked > fine. That was before I changed anything. As if it had repaired itself. > The only thing I could see is a crack in the plastic of the X-capacitor. > Snipped the thing out, measured, has almost 0.28uF capacitance (27% more > than stated) and no leakage current. There is another X-cap and two > Y-caps inside a canned IEC receptacle but those can't be the culprits > because that is on the line side of the power switch. > > Is it possible that an X-cap self-heals to the point where you can > barely see a thing, yet release a serious plume of smoke? It is a Rifa > GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there.
They're supposed to self heal Smoke has low density, you can fit a lot of smoke precursor into a small space. if it's got a crack it should definately be replaced, why not do some destructive testing and see if it can withstand the test voltage required and if it makes the right sort of wrong smell. -- &#9858;&#9859; 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
On Sat, 21 Sep 2013 22:20:41 -0400, the renowned Martin Riddle
<martin_rid@verizon.net> wrote:

>On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid> >wrote: > >>Folks, >> >>This afternoon I took the old HP-4191A apart. Yesterday in the middle of >>some measurements it went pop-pop-pop, loud, like firecrackers. I ran >>over and turned it off, upon which the popping stopped. An immense >>amount of light-gray smoke wafted out and it had an odd stench to it. >>The stench lingered for hours. >> >>I can't find any source and upon powering it up the analyzer worked >>fine. That was before I changed anything. As if it had repaired itself. >>The only thing I could see is a crack in the plastic of the X-capacitor. >>Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >>than stated) and no leakage current. There is another X-cap and two >>Y-caps inside a canned IEC receptacle but those can't be the culprits >>because that is on the line side of the power switch. >> >>Is it possible that an X-cap self-heals to the point where you can >>barely see a thing, yet release a serious plume of smoke? It is a Rifa >>GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there. > >They are Self-Healing to the point that they don't pose a safety risk. ><http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf> > >Cheers
Doesn't the UL standard prohibit "excessive" amounts of smoke? But those Rifa parts are pretty ancient. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Sat, 21 Sep 2013 22:28:54 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Sat, 21 Sep 2013 22:20:41 -0400, the renowned Martin Riddle ><martin_rid@verizon.net> wrote: > >>On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid> >>wrote: >> >>>Folks, >>> >>>This afternoon I took the old HP-4191A apart. Yesterday in the middle of >>>some measurements it went pop-pop-pop, loud, like firecrackers. I ran >>>over and turned it off, upon which the popping stopped. An immense >>>amount of light-gray smoke wafted out and it had an odd stench to it. >>>The stench lingered for hours. >>> >>>I can't find any source and upon powering it up the analyzer worked >>>fine. That was before I changed anything. As if it had repaired itself. >>>The only thing I could see is a crack in the plastic of the X-capacitor. >>>Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >>>than stated) and no leakage current. There is another X-cap and two >>>Y-caps inside a canned IEC receptacle but those can't be the culprits >>>because that is on the line side of the power switch. >>> >>>Is it possible that an X-cap self-heals to the point where you can >>>barely see a thing, yet release a serious plume of smoke? It is a Rifa >>>GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there. >> >>They are Self-Healing to the point that they don't pose a safety risk. >><http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf> >> >>Cheers > >Doesn't the UL standard prohibit "excessive" amounts of smoke? But >those Rifa parts are pretty ancient. > > >Best regards, >Spehro Pefhany
Some smoke is ok, It is the flame and sustained smoking that throw red flags for UL. X caps fail open, so they should not smoke for long. If Joerg left the power on long enough, he probably would not have seen flames or more smoke. I would have had a 'Oh sh... moment and turned the power off too" ;D Cheers
On Sat, 21 Sep 2013 23:02:48 -0400, the renowned Martin Riddle
<martin_rid@verizon.net> wrote:

>On Sat, 21 Sep 2013 22:28:54 -0400, Spehro Pefhany ><speffSNIP@interlogDOTyou.knowwhat> wrote: > >>On Sat, 21 Sep 2013 22:20:41 -0400, the renowned Martin Riddle >><martin_rid@verizon.net> wrote: >> >>>On Sat, 21 Sep 2013 15:17:34 -0700, Joerg <invalid@invalid.invalid> >>>wrote: >>> >>>>Folks, >>>> >>>>This afternoon I took the old HP-4191A apart. Yesterday in the middle of >>>>some measurements it went pop-pop-pop, loud, like firecrackers. I ran >>>>over and turned it off, upon which the popping stopped. An immense >>>>amount of light-gray smoke wafted out and it had an odd stench to it. >>>>The stench lingered for hours. >>>> >>>>I can't find any source and upon powering it up the analyzer worked >>>>fine. That was before I changed anything. As if it had repaired itself. >>>>The only thing I could see is a crack in the plastic of the X-capacitor. >>>>Snipped the thing out, measured, has almost 0.28uF capacitance (27% more >>>>than stated) and no leakage current. There is another X-cap and two >>>>Y-caps inside a canned IEC receptacle but those can't be the culprits >>>>because that is on the line side of the power switch. >>>> >>>>Is it possible that an X-cap self-heals to the point where you can >>>>barely see a thing, yet release a serious plume of smoke? It is a Rifa >>>>GPF-series film cap 0.22uF/250VAC with all kinds of agency logos on there. >>> >>>They are Self-Healing to the point that they don't pose a safety risk. >>><http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf> >>> >>>Cheers >> >>Doesn't the UL standard prohibit "excessive" amounts of smoke? But >>those Rifa parts are pretty ancient. >> >> >>Best regards, >>Spehro Pefhany > >Some smoke is ok, It is the flame and sustained smoking that throw red >flags for UL. X caps fail open, so they should not smoke for long. > >If Joerg left the power on long enough, he probably would not have >seen flames or more smoke. > >I would have had a 'Oh sh... moment and turned the power off too" ;D > >Cheers
Presumably his immediate objective was to interrupt the proximate cause of the popping and smoking rather than to fully test those ancient capacitors to UL standards. ;-) Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com