metallized polypropylene capacitors for DC supply
metallized polypropylene capacitors for DC supply
(OP)
Hi I am looking for a metal pol capacitors for DC supply, I am rectifying 28VAC with a bridge rectifier (more efficient than single diode) and will attempt to "smooth" the rectified voltage with a capacitor bank. I have looked at some metal poly capacitors. I would like 60-70WVDC at 1000uF, but in a small form factor. for example, something smaller than http://www.icwltd.co.uk/smf.html# (click on technical details).
Any help on vendors would be greatly appreciated.
Any help on vendors would be greatly appreciated.





RE: metallized polypropylene capacitors for DC supply
*Polysomething: Polycarbonate? Polystyrene? Polyester? Polypropylene?
Do you need very low ESR and ESL? Very high ripple current rating? Very high ripple frequency? Elevated temperature? There is a lot of detail which is missing - it would be easier to help if we knew what was going on!
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I don't suffer from insanity. I enjoy it...
RE: metallized polypropylene capacitors for DC supply
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I don't suffer from insanity. I enjoy it...
RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
400 Hz, reducing cap-s and transformers etc.
Plesae read FAQ240-1032
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RE: metallized polypropylene capacitors for DC supply
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: metallized polypropylene capacitors for DC supply
Gunnar Englund
www.gke.org
RE: metallized polypropylene capacitors for DC supply
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: metallized polypropylene capacitors for DC supply
is 10x25 mm. A solid iron cylinder of this size would be
less than 50 gram.
It must be air filled to remove the pressure from the C.
I didn't calcilate it but I am willing to bet that less
than 4 mm. thick wall will be enough.
Plesae read FAQ240-1032
WEB: <http://geocities.com/nbucska/>
RE: metallized polypropylene capacitors for DC supply
survive this pressure either e.g. transistors and IC-s.
Why not use DC ?
Plesae read FAQ240-1032
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RE: metallized polypropylene capacitors for DC supply
DC sounds good. But there is probably a voltage drop issue involved.
What about supercaps? They are compact, no voids. Need to use several in series and a potential equalizer, though.
Gunnar Englund
www.gke.org
RE: metallized polypropylene capacitors for DC supply
There are reflectors on the marker guaranted to 6000 m
with glass lens - see at <www.deepsea.com/sa_hmi.html>
-- so it is possible to build a case for 5000m.
Plesae read FAQ240-1032
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RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
I agree with nbucksa that the rest of the electronics will need some help to survive this pressure. One technique used in CSMU's is to contain the electronics in a titanium container filled with silicon gel. I don't know of any small metal pol capacitors though and so the suggestion of a 3 phase supply has a lot of merit as the filtering requirements are a lot less. 400Hz would simplify things even more but you will need to treat the 15,000 ft cable as a transmission line to control the losses which would otherwise be large. There are a few challenges here.
RE: metallized polypropylene capacitors for DC supply
For use under pressure (downhole), the lid had a hole in it and the cavity was filled with silicone oil of some kind.
RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
Are you tied to 28V AC? If this is for a production part have you considered a hybrid as a power converter? They can be packaged to suit just about any environment.
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I don't suffer from insanity. I enjoy it...
RE: metallized polypropylene capacitors for DC supply
2.) At 400 Hz the 15,000 ft is .006 lambda - no reason to
handle it as tr. line.
3.) BRIAN: if the Ti container carries the pressure the Si gel is only for heat xfer.
4.) What about the communication signals, connectors, cables? Fiber optics or Cu ?
5) I submit that each component must be evaluated for the
pressure and the design is far from trivial...
Plesae read FAQ240-1032
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RE: metallized polypropylene capacitors for DC supply
Have to agree with all you say although wrt the CSMU the other specs it must pass include 2 hr @ 1,100 degC + 9 hr @ 260 degC + absolutely huge shock and vib so the silicon in that case is not for heat transfer but impact protection and heat blocking. Virtually no internal heat is generated anyway.
RE: metallized polypropylene capacitors for DC supply
at 1100 C Au,Al,Cu are molten and there is no polypropylene
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RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
all of these are interesting but mostly irrelevant --
they just show what careful design can do...
Fuse:
FYI: <www.sensotec.com> has .5" to 4" displacement sensors
for undersea application up to 3500 PSI.
Plesae read FAQ240-1032
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RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
RE: metallized polypropylene capacitors for DC supply
I can see aluminum electrolytics having the void issues you mentioned but what about a tantalum? I am not 100% sure but their construction might be void free. However they have other issues and failures in them are not generally pretty. I am assuming that you have already considered these and decided they don't fit the application.
Given that it might be worthwhile to consider some other more off the wall type solutions.
You could look at an assembly with ceramic caps. Surface mount cermaics with 1uF capacitance in 1206 packages are very common. Using double sided boards with vias under pads and internal planes it should be possible to get 1000uF down to about a 4x6x2 package. Still not small but less than what I think you will find with poly caps. Some creative board layout or >1uF caps might get this considerably smaller.
You might also consider putting some aluminum electrolytic capacitors under oil and pulling a deep vacuum to remove voids. Not sure if this would work but it might. You would need to be sure that the oil you are using is compatible with the oil the cap manufacturer uses. Also, aluminum electrolytics do vent as they age and I am not sure if they produce gas internally. That might be a problem. Information nn their aging should be readily availble from a cap manufacturer or someone more familiar with their aging process.
Just some thoughts. Sounds like a tough issue. Good luck.