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Capacitor Plage - Premature Electrolytic Capacitor Failure

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Laplacian

Electrical
Jul 15, 2002
246
US
Over the past several years, our industrial facility has experienced many electronics failures where the root cause has been capacitor failure due to electrolyte dry-out. The problem has been seen in power supplies for PLC's, protective relays, and process control equipment installed in the later 1990's.

I began investigating a recent incident, and suddenly remembered all the issues around motherboards and computer power supplies a few years ago. Our equipment is the same age as the failed computer equipment. I found an interesting wikipedia article that mentioned an IEEE Spectrum article from February 2003, titled "Bad Capacitors Mucking Up Motherboards".

This article only dealt with the personal computer side if the issue.

The goal of this posting (which will be cross posted into relevant forums) is to determine the extent of industrial failures and to estimate an approximate window of when the bad equipment was installed. This is due to the relative silence from the capacitor and equipment manufacturers on the issue.

The questions are as follows:

1. Has your facility experienced multiple failures with the root cause being bad capacitors causing voltage instability?

2. If yes to #1, what year was the device manufactured?

3. If yes to #1, what as the manufacturer (if it is appropriate to tell) or what was the equipment type.

Please also share any further information you may have on the subject. We are looking to determine the extent of this phenomena and our exposure to future events; one event can cost our industry several M$'s. Thanks in advance for any information.
 
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Laplacian,

I have had no more than perhaps ten cases of bad electrolythic capacitors over the three+ decades that I have been exposed to equipment failure in paper mills, steel works, power plants, workshops and offices.

The ones I remember are:

One Measuring machine of Swiss origin. The capacitor was a Philips type and the age was well over twenty years. The ripple current had heated it to the extent that the wire insulation had turned brown/black. Natural aging, I would say.

One press with linear scales and automatic positioning. Capacitor in PSU gone bad. Also natural aging.

One old PLC (Elektronlund) with bad capacitor. Natural aging again.

Eleven HP laser printers where the capacitors exploded after very short time. Reason here was severe notching of mains voltage due to heavy (800 kW) thyristor controlled heater on distribution transformer secondary. Mistake by the electricity company. The transformer was supposed to supply the industrial load only, but did double duty supplying a research office.

I cannot recall any capacitors that were bad quality. There is some concern with DC link capacitors in PWM frequency inverters. But I have yet to find one that really causes problem. The oldest inverters I get in touch with are ABB YRRA and Siemens Simovert P from the eighties.

This will be a very interesting thread, I urge all and everyone that has experienced electrolythic capacitor failures to write about it here.

Gunnar Englund
 
Various dried out smpsu electrolytics in video recorders. Mostly 85 deg C types.

Many years ago, I remember mains filter capacitors in vacuum tube tv sets exploding. Well the ends blew off with a bang... caused by age in waxed paper capacitors.

(Remember them? Horrible waxy yellow things, always sticky).
 
Oh. And dried out capacitors in fruit machine power supplies. Peculiar failure mode where the ripple current rating was reduced. Presumably esr related because the capacitance value was ok. Did very strange things to the waveform of the ripple on the rail.
 
Thankyou for your input skogsgurra.

I have directed that future posts in the other forums be directed here.

The interesting wikipedia link is here:

If you have a subscription, the IEEE Spectrum paper is rerferenced in the original post.
 
If memory serves, weren't issues tied to only one electrolyte manufacturer? I believe a few ticked off employees walked out with the "formula" and sold it to a competitor. That competitor attempted to recreate the electrolyte (and sold it as a quality replacement at a lower price), but screwed up the creation process. Every cap made with those batches of electrolyte had severely reduced specs as the years went on. Even some of the higher quality cap makers purchased the bad electrolyte.

Of course, this is all from memory...


Dan
Owner
 
Yes, the formula (incorrect) was supposedly stolen and sold to the lower cost mfg's from Taiwan. Since there has been such silence from the manufacturers and it is somewhat documented that this happened, I'm trying to determine the extent.

Right now, I know one protective relay manufacturer, of whose we have very many, and the consequences of false tripping are high. The costs associated with repair/replacement are high and a better understanding of failure probability would help make the case for corrective action.
 
For years (last 10-15) we have been replacing dried out caps in video monitors of coin operated arcade game (yes, Pacman, defender, etc). The problem is so bad that there are companies that sell replacement caps in packages specific to the monitor model and manufacture. Some of the problems were created by the monitor manufactures, by placing caps next to heat sinks or high wattage resistors but most dried out caps were not because of this problem. The caps were manufactured by many different companies under many different brand names.
 
This is very interesting. It seems that capacitors used in games and other consumer products are lower quality than those used in industrial and professional equipment. And that's only what one would expect.

I think that my lack of bad experiences with capacitors comes from the fact that I am not asked to find what's wrong with consumer products. I wonder why my radios, TV sets and other consumer products also behave relatively well? I remember having just one bad capacitor in the power supply back in the seventies. The TV set was so old that it had electron tubes in it.

Gunnar Englund
 
The difference between consumer and industrial products may have been different at one time, but the global market place has skewed the lines somewhat. Most capacitors are now made in Taiwan or Japan with no distinction between industrial and consumer.

I believe some of the larger industrial electronics manufacturers have outsourced some of the subassemby for their devices with cost as the primary factor. The units come in and pass Q/A testing, but rapidly fail when placed into service.

I found a couple more interesting links.


There are several websites dedicated to motherboard failures on this issue.

The other text I've found said it's only the high water content (40% - 70%) aquious electrolyte aluminum capacitors that are failing. The other two aquious types are Dipropyl Ketone and Ethylene Glycol with less than 25% water content.

Not suprisingly, the higher water content units are cheaper. I suspect these units are being substituted to save costs while meeting specification.
 
Surface mount Al electrolytics in handheld video recorders generally have a bad press, especially for leaking electrolyte all over the pcb & disolving the pth vias...

The 105 deg C versions are allegedly better.



 
Forming capacitors is common in large 480V motor drives to keep them from exploding after repair. I have also seen some smaller supplies having a forming routine option.

I have no idea what the minimum form time/curve per volt/farad would be to have some meaningful value. It would probably be to long for a consumer item.

Barry1961
 
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