I need to identify this component, I suspect it is a capacitor... - Page 1
Forum section: electronics / beginners

author: Greate
author_rank: Contributor
timestamp: March 09, 2012, 10:33:41 pm
content: I need to identify this component, I suspect it is a capacitor, but what is the value? What is it made off?

author: Psi
author_rank: Super Contributor
timestamp: March 09, 2012, 10:38:28 pm
content: It's 8 microfarad at 5000V DCMFD = old way of saying microfaradWVDC = working voltage direct currentThat cap is quite dangerous when charged.Also high voltage caps have a tendency to charge themselves up somewhat, even when not connected. So its a good idea to keep it shorted with some wire. (After you safely confirm it's not charged and discharge it properly)I would post an informative video about highvoltage DC caps but sadly photonicinduction is no more

author: grenert
author_rank: Frequent Contributor
timestamp: March 10, 2012, 02:51:37 am
content: It looks like an old oil capacitor.

author: T4P
author_rank: Super Contributor
timestamp: March 10, 2012, 02:57:51 am
content: 40 millicoulombs and 100 joulesOh dear , that's dangerous .

author: Psi
author_rank: Super Contributor
timestamp: March 10, 2012, 04:07:25 am
content: 100 joules is significant but smallish compared to modern caps of the same physical size.The danger is because it can dump all that energy into a human body very easily due to its high voltage.

author: T4P
author_rank: Super Contributor
timestamp: March 10, 2012, 04:26:53 am
content: Quote from: Psi on March 10, 2012, 04:07:25 amYes .

author: Greate
author_rank: Contributor
timestamp: March 10, 2012, 04:49:42 am
content: Thank you so much for the information, specially mentioning how dangerous it is. What could be it's storage life? How could I test it if it is still in good condition? I don't have any idea how old it is. I have tried to use a capacitance meter and it read 8.07 mF. Just in case it is not good anymore, what could be the proper disposal of this capacitor? I just worry about the chemical used as the dielectric.

author: metalphreak
author_rank: Frequent Contributor
timestamp: March 10, 2012, 05:18:24 am
content: Quote from: Psi on March 09, 2012, 10:38:28 pmThe grounding strap in the photo that's broken was probably serving that exact purpose.

author: T4P
author_rank: Super Contributor
timestamp: March 10, 2012, 05:35:13 am
content: Quote from: Greate on March 10, 2012, 04:49:42 amOHMYLORD , 8mF or 8uF ? I know PCB isn't safe but it's kinda safe to say that because it's insulated . But if it's oil then no problem .

author: Psi
author_rank: Super Contributor
timestamp: March 10, 2012, 06:22:45 am
content: Quote from: Dave.S on March 10, 2012, 05:35:13 amdefinitely 8uf

author: SeanB
author_rank: Super Contributor
timestamp: March 10, 2012, 09:24:17 am
content: Shelf life on these old paper units is essentially forever, or until the case rusts through. This is a paper dielectric capacitor, and most likely the actual insulation is provided by oil. Only issue is the oil will be a PCB compound, so if you smell oil on the unit, or it is leaking oil then you need to handle as hazardous material. If it is not leaking it will be fine, I have never seen these fail other than from physical damage or dead seals, unless you apply more than double the rated voltage ( done for 30s during manufacture) for an extended time, or drive high current through it ( I have a 0.1uF 2kV mica capacitor that is rated for 11A RMS at 30MHz) to overheat it. These were normally used on high power valve transmitters, and are still used, even if the units are getting close to 50 years old, they rarely give problems.

author: T4P
author_rank: Super Contributor
timestamp: March 10, 2012, 03:58:38 pm
content: ^ Nothing like a big fat ol' oil cap to put at the corner of your workshop !But the PCB compound is something substantial to be worried about . (If they do leak)And remember to test if it leaks whether it is a oil or PCB , oils burn when lighted but PCB's don't . Just make sure if you dip the oil in the tissue and it is the oil burning not the tissue .

author: Greate
author_rank: Contributor
timestamp: March 10, 2012, 06:54:23 pm
content: Yes 8 uf. Sorry about the wrong abreaviation above.Sent from my A100 using Tapatalk

author: Greate
author_rank: Contributor
timestamp: March 11, 2012, 02:27:06 am
content: And by the way where doese this capacitor is usually used for?Sent from my A100 using Tapatalk

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2012, 01:44:24 pm
content: Normally used in equipment that has large glass bottles in it, with even larger glass blocks with massive copper fins, all with a big fan for cooling said glassware. Will have a name on the front like Collins, and will have a mains fuse of 30A plus. Normally has more than 100kg of steel panels on the outside.High power AM or FM transmitters if you have never seen the above.

author: tecman
author_rank: Frequent Contributor
timestamp: March 12, 2012, 06:53:40 pm
content: Quote from: Psi on March 10, 2012, 04:07:25 amActually it packs quite a bit more punch. Since joules are 1/2 CV^2, voltage increases by the square. Lower voltage, although higher capacitance, are only a linear increase with capacitance.paul

author: T4P
author_rank: Super Contributor
timestamp: March 12, 2012, 07:43:28 pm
content: Quote from: tecman on March 12, 2012, 06:53:40 pmDoesn't matter , when charged up to 5000V can deliver nearly full current through your body ! ( If you are wet that is )0.5amps if you are wet ... HOLY SHIT !

author: Unknown
author_rank: Unknown
timestamp: March 12, 2012, 11:15:00 pm
content: Quote from: Dave.S on March 12, 2012, 07:43:28 pmThe human body can build up a charge of up to about 10 kV. Shaking someone's hand while touching a grounded surface with your other hand would send 1 A through your chest. Holy shit, I will never shake anybody's hand ever again!There's a difference between electric potential and energy, which is why we survive despite the presence of large electrostatic potentials all around us. The capacitance tends to be extremely tiny, about 100 pF in the case of the human body.

author: westfw
author_rank: Super Contributor
timestamp: March 13, 2012, 01:33:57 am
content: When you start talking about 'static electricity', like you can get by scuffing your leather shoes over the wool rug, you start talking about the energy of the discharges (in Joules) rather than instantaneous currents. A discharge of about 10J is considered potentially fatal (Moore, "Electrostatics.") A human body has a capacitance of about 100pF, so charged to 10kV, you have an energy (0.5*CVV) of about 0.005J; not a problem. This cap, at 8uF and 5000V, has a capacitance 80000 times bigger, and stores 100J. It'll zap you real good!