Differences in Capacitors

[john_g]

Hi

I have a question about capacitors. I am comparing 2 capacitors:
Cap #1 Arcotronics MKP C.4G, 10uf +-5% 600v
Cap #2 Vishay MKT1813 10uf, +-10% 250v

Using a quad filer coil, windings arranged as: 1 winding used as the coil power, the other 3 winding are joined together, one end connected to a capacitor via a single diode, the other end to the other side of the capacitor.

To pump up the caps I make and break the circuit through the single windings, 10.v vdc and can observe on a voltmeter the voltage rising.

What I have noticed is that when charging the capacitors up to say 200v, I get an impressive flash discharge from Cap #1, but at the same voltage a tiny spark from Cap#2. Sorry if this is obvious but why is this?

Kind regards

John

[Farmhand]

Hi John, I have noticed similar things and read of similar also and putting aside a defective cap I can think of 4 possible reasons.

1- The caps may have a different actual value than what is "advertised".
2- Cap 2 failed to receive all the energy you presented to it.
3- The caps have different discharge characteristics.
4- The caps legs are made from a different material or different coatings to each other.

or a combination.

Cheers

P.S. For some reason I couldn't find a datasheet for those caps.

[john_g]

Hi John, I have noticed similar things and read of similar also and putting aside a defective cap I can think of 4 possible reasons.

1- The caps may have a different actual value than what is "advertised".
2- Cap 2 failed to receive all the energy you presented to it.
3- The caps have different discharge characteristics.
4- The caps legs are made from a different material or different coatings to each other.

or a combination.

Cheers

P.S. For some reason I couldn't find a datasheet for those caps.

Farmand

Thanks for that. I have checked both via a DMM for capacitance and both are about the same - so they would appear to be working. The caps not working so well, I have a few of, and all perform the same. As they build up the voltage ok I suspect there is some clue in your points 3 and 4, I will see if I can find some spec sheets. Maybe this explains why some people have no luck with cap charging batteries.

Regards

John

[Farmhand]

No problem John,

I did assume though that the caps are both the same type. I've had mixed results myself capacitor charging, with a radiant source I prefer to use a direct output with no cap. I'm having trouble getting my cap discharge setup to discharge at a lower frequency than my SSG, i'm starting to think a timed charge is better than what i'm doing now.

[john_g]

Data sheets

Hi farmhand

I have found links to data sheets, though I am not really sure what I sould be looking for to see a difference, links below:

http://www.vishay.com/docs/26013/mkt1813.pdf

http://www.digikey.com/Web%20Export/...lectronics.pdf

Regards

John

[gyula]

Hi John,

The difference must be in their differing ESR values. (ESR=Equivalent Series Resistance, see the Figure and explanation at the bottom of this link: Loss tangent - Wikipedia, the free encyclopedia

For the Arcotronics MKP C4G type the Dissipation Factor (tangent of loss angle) is less than 5*10^-4 at 1kHz (Page 17, in Technical Data tabelle)
while for the Vishay MKT1813 type this value is given as 100*10^-4 at 1kHz (Page 2, in Specific Reference Data).

The reciprocal value of these factors gives the Q, the quality factor for these capacitors, which is higher than 2000 for the MKP type and about 100 only for the MKT type. A 20 times difference and this is what you can see in the differing sparkings when they are discharged.

The ESR value is given for the MKP as 5.3 milliOhm at 100kHz (Page 20 for the 600V C4GAHUD5100AA3J if you have this type) while this data is missing for the Vishay cap, this also means the selected Arcotronics (now Kemet) type is better, they dare to specify it at even 100kHz.

rgds, Gyula

PS: Whenever you wish to use capacitors, try to study their data sheet for their ESR and / or Dissipation Factor and choose accordingly. Even for electrolytic caps there are low ESR types (but not really over 160-200V DC working voltage ratings but lower).

[john_g]

Hi John,

The difference must be in their differing ESR values. (ESR=Equivalent Series Resistance, see the Figure and explanation at the bottom of this link: Loss tangent - Wikipedia, the free encyclopedia

For the Arcotronics MKP C4G type the Dissipation Factor (tangent of loss angle) is less than 5*10^-4 at 1kHz (Page 17, in Technical Data tabelle)
while for the Vishay MKT1813 type this value is given as 100*10^-4 at 1kHz (Page 2, in Specific Reference Data).

The reciprocal value of these factors gives the Q, the quality factor for these capacitors, which is higher than 2000 for the MKP type and about 100 only for the MKT type. A 20 times difference and this is what you can see in the differing sparkings when they are discharged.

The ESR value is given for the MKP as 5.3 milliOhm at 100kHz (Page 20 for the 600V C4GAHUD5100AA3J if you have this type) while this data is missing for the Vishay cap, this also means the selected Arcotronics (now Kemet) type is better, they dare to specify it at even 100kHz.

rgds, Gyula

PS: Whenever you wish to use capacitors, try to study their data sheet for their ESR and / or Dissipation Factor and choose accordingly. Even for electrolytic caps there are low ESR types (but not really over 160-200V DC working voltage ratings but lower).

Gyula

Many thanks for that. Learn a little bit more each day! Not sure of the spec that John Bedini uses (they are yellow) however I have found as has Farmhand that there is a difference between caps that appear to be the same - ESR, the way forward - check.

Again thanks.

Regards

John

[greenliving]

Hi John,

The difference must be in their differing ESR values. (ESR=Equivalent Series Resistance, see the Figure and explanation at the bottom of this link: Loss tangent - Wikipedia, the free encyclopedia

For the Arcotronics MKP C4G type the Dissipation Factor (tangent of loss angle) is less than 5*10^-4 at 1kHz (Page 17, in Technical Data tabelle)
while for the Vishay MKT1813 type this value is given as 100*10^-4 at 1kHz (Page 2, in Specific Reference Data).

The reciprocal value of these factors gives the Q, the quality factor for these capacitors, which is higher than 2000 for the MKP type and about 100 only for the MKT type. A 20 times difference and this is what you can see in the differing sparkings when they are discharged.

The ESR value is given for the MKP as 5.3 milliOhm at 100kHz (Page 20 for the 600V C4GAHUD5100AA3J if you have this type) while this data is missing for the Vishay cap, this also means the selected Arcotronics (now Kemet) type is better, they dare to specify it at even 100kHz.

rgds, Gyula

PS: Whenever you wish to use capacitors, try to study their data sheet for their ESR and / or Dissipation Factor and choose accordingly. Even for electrolytic caps there are low ESR types (but not really over 160-200V DC working voltage ratings but lower).

Very nice points. Also try to reconsider your wiring. Study if you are giving lot of power to that capacitor then it can't send power to the next capacitor, so the power is stock in there, that makes it burn.

[Farmhand]

Yellow Caps

Hi all, That is very handy information. So the ESR affects the discharge rate or causes energy wastage when charging or both?

I have a 15 MFD yellow cap that I can't find a data sheet for, it makes nice pretty sparks when discharged, I don't have much luck with capacitor datasheets for some reason.

Written on the cap is,

931C4W15-1K
15MFD +/- 10%
400VDC 85*c
CDET. LC

Is the C4 part significant? I see it for the MKP type John has as well as for mine.

Cheers

[gyula]

Hi all, That is very handy information. So the ESR affects the discharge rate or causes energy wastage when charging or both?

I have a 15 MFD yellow cap that I can't find a data sheet for, it makes nice pretty sparks when discharged, I don't have much luck with capacitor datasheets for some reason.

Written on the cap is,

931C4W15-1K
15MFD +/- 10%
400VDC 85*c
CDET. LC

Is the C4 part significant? I see it for the MKP type John has as well as for mine.

Cheers

Hi,

You can consider ESR as if you were to connect a normal resistor in series with the capacitor, the value of the resistor is being the ESR, it is definitely a loss. So the answer to your first question above is yes, both.

You 15uF capacitor most likely was manufactured by Cornell Dubilier but strangely enough the series 931 is left out from their range now, see here:
Capacitors by Series/Type - Aluminum, Film, Mica, High Voltage, Ceramic, Tantalum & more - CDE.com

The best shot near to it is 932C4W15J-F, see Page 2 here:
http://www.cde.com/catalogs/932C.pdf and it has a 3.1 milliOhm ESR at 100kHz frequency.

So I do not think it is a Kemet type where the C4 series has several members designated with letters but the 'C4W' is not included among them.
You may wish to write a letter to Cornell Dubilier asking for possible data sheet on 931C4W15-1K or its substitution part, Contact Us - Directory By Department - CDE.com

By the way, it is good to know that ESR gets reduced if several capacitors are connected in parallel. Just like for normal paralleled resistors the result is always lower than any one of the members in the paralleled group.

Gyula

[Farmhand]

Thank you very much gyula, Yes it is a good cap though it's not much use on it's own.

By the way, it is good to know that ESR gets reduced if several capacitors are connected in parallel. Just like for normal paralleled resistors the result is always lower than any one of the members in the paralleled group.

Regards