DRSSTC capacitor
Thomas W, Sun Feb 09 2014, 05:40PMHello,
How good would a capacitor such as this be for DRSSTC use?
It looks fairly good, but im curious if it would be able to deal with the current flowing through it, or even if it is the right type of capacitor
Thanks,
Thomas
Re: DRSSTC capacitor
Antonio, Sun Feb 09 2014, 11:05PM
The capacitance is a bit small (10 nF), and the voltage is unnecessarily high.
Antonio, Sun Feb 09 2014, 11:05PM
The capacitance is a bit small (10 nF), and the voltage is unnecessarily high.
Re: DRSSTC capacitor
Sigurthr, Mon Feb 10 2014, 04:50AM
But, you can still make use of that by using a large inductance primary and long burst lengths. The limiting factor will be dielectric heating, so place a blast shield around it and watch temps remotely.
Sigurthr, Mon Feb 10 2014, 04:50AM
But, you can still make use of that by using a large inductance primary and long burst lengths. The limiting factor will be dielectric heating, so place a blast shield around it and watch temps remotely.
Re: DRSSTC capacitor
Thomas W, Mon Feb 10 2014, 10:44AM
Hmm, in that case, i shall pass on buying it, i had saw it on ebay.
Thomas W, Mon Feb 10 2014, 10:44AM
Hmm, in that case, i shall pass on buying it, i had saw it on ebay.
Re: DRSSTC capacitor
omegalabs, Mon Oct 13 2014, 02:54PM
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
omegalabs, Mon Oct 13 2014, 02:54PM
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
Re: DRSSTC capacitor
Wolfram, Mon Oct 13 2014, 04:39PM
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these
would be much better value for money.
Wolfram, Mon Oct 13 2014, 04:39PM
omegalabs wrote ...
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these
would be much better value for money.Re: DRSSTC capacitor
omegalabs, Mon Oct 13 2014, 06:15PM
This snubber is actually more expensive for the same voltage/capacitance (also any other MMC construction is). I have an idea for an ultra reliable and cheap home made cap (LDPE plates + aluminum strip+silicone oil, it works great), but it needs a good container, and it's pretty big for a DRSSTC. It would be possible to make it better, but I can buy only 1mm thick PE plates here, but actually 0,5mm thickness should be enough for any kind of DRSSTC from PE. Looks like it's better to do it myself.
omegalabs, Mon Oct 13 2014, 06:15PM
Wolfram wrote ...
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these would be much better value for money.
omegalabs wrote ...
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these
would be much better value for money.This snubber is actually more expensive for the same voltage/capacitance (also any other MMC construction is). I have an idea for an ultra reliable and cheap home made cap (LDPE plates + aluminum strip+silicone oil, it works great), but it needs a good container, and it's pretty big for a DRSSTC. It would be possible to make it better, but I can buy only 1mm thick PE plates here, but actually 0,5mm thickness should be enough for any kind of DRSSTC from PE. Looks like it's better to do it myself.
Re: DRSSTC capacitor
Wolfram, Mon Oct 13 2014, 07:37PM
Something is a bit fishy with the cap in the auction. In the eBay picture, the cap is clearly labelled KMOP754, according to the Condenser Products website the KMOP series are "Kraft/Polyester" capacitors intended for "DC filter, limited AC, and pulse discharge applications", even though it's listed as polypropylene on eBay. The peak/RMS voltage rating confusion I mentioned earlier is also a bit suspicious.
Assuming you needed 750nF at 25kV DC (which this capacitor is, assuming the Peak rating stamped on the cap is a DC rating, the actual DC rating might be lower), you would need strings of 25 of the RBPS caps in series. 10 of these strings in parallel would give you 800nF, with an unprecedented RMS current rating of 225 A, for a total cost of 350 dollars. In my experience they accept lower offers as well, so it could end up being even cheaper still.
One problem is that they only have 200 of these caps listed, in two separate auctions. But if you could relax the specifications a bit, you could probably even get by with 100 of them. For example configured as sixteen in series by six in parallel, yielding 750nF at 16kV DC. These capacitors are rated for 530V RMS each, so the bank would be rated for 8.5kV RMS, or 12kV peak, with a very good safety margin. This corresponds to 2800 A peak in the primary, if you're running at 50 kHz.
Wolfram, Mon Oct 13 2014, 07:37PM
omegalabs wrote ...
This snubber is actually more expensive for the same voltage/capacitance (also any other MMC construction is).
Wolfram wrote ...
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these would be much better value for money.
omegalabs wrote ...
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
Has someone any experience with these cap?
Cap
I'm planning a large DRSSTC, and this cap looks almost perfect, but it's too expensive just to order one for testing.
The auction says 25 kV RMS, but the label on the cap in the picture says 25 kV peak, big difference. There's also no stated RMS current rating, considering the considerable cost I would not gamble on using it in a big DRSSTC. Especially since you can get proven caps for a lower price.
Something like a bank of these
would be much better value for money.This snubber is actually more expensive for the same voltage/capacitance (also any other MMC construction is).
Something is a bit fishy with the cap in the auction. In the eBay picture, the cap is clearly labelled KMOP754, according to the Condenser Products website the KMOP series are "Kraft/Polyester" capacitors intended for "DC filter, limited AC, and pulse discharge applications", even though it's listed as polypropylene on eBay. The peak/RMS voltage rating confusion I mentioned earlier is also a bit suspicious.
Assuming you needed 750nF at 25kV DC (which this capacitor is, assuming the Peak rating stamped on the cap is a DC rating, the actual DC rating might be lower), you would need strings of 25 of the RBPS caps in series. 10 of these strings in parallel would give you 800nF, with an unprecedented RMS current rating of 225 A, for a total cost of 350 dollars. In my experience they accept lower offers as well, so it could end up being even cheaper still.
One problem is that they only have 200 of these caps listed, in two separate auctions. But if you could relax the specifications a bit, you could probably even get by with 100 of them. For example configured as sixteen in series by six in parallel, yielding 750nF at 16kV DC. These capacitors are rated for 530V RMS each, so the bank would be rated for 8.5kV RMS, or 12kV peak, with a very good safety margin. This corresponds to 2800 A peak in the primary, if you're running at 50 kHz.
This snubber is actually more expensive for the same voltage/capacitance (also any other MMC construction is). I have an idea for an ultra reliable and cheap home made cap (LDPE plates + aluminum strip+silicone oil, it works great), but it needs a good container, and it's pretty big for a DRSSTC. It would be possible to make it better, but I can buy only 1mm thick PE plates here, but actually 0,5mm thickness should be enough for any kind of DRSSTC from PE. Looks like it's better to do it myself.It's a nice idea, but if I calculated right, you need 37 square meters of 1mm PE to get 750nF.
Re: DRSSTC capacitor
omegalabs, Mon Oct 13 2014, 08:08PM
Oh ok the price is for 50 pieces, I didn't saw that.
16kVDC should be enough for the cap, my plan is a CM600 full bridge around 10kW.
This is why I'm looking for thinner PE sheets, 0,5mm would be the ideal thickness. Half weight, and half the needed surface area, so it would be extremely cheap.
37 square meter is also not a big deal, but it needs a lot of work to assemble hundreds of plates together. It would be big and heavy.
omegalabs, Mon Oct 13 2014, 08:08PM
Oh ok the price is for 50 pieces, I didn't saw that.
16kVDC should be enough for the cap, my plan is a CM600 full bridge around 10kW.
It's a nice idea, but if I calculated right, you need 37 square meters of 1mm PE to get 750nF.Yes, originally I made this cap for spark gap coil, where it works really good in a few 10nF range.
This is why I'm looking for thinner PE sheets, 0,5mm would be the ideal thickness. Half weight, and half the needed surface area, so it would be extremely cheap.
37 square meter is also not a big deal, but it needs a lot of work to assemble hundreds of plates together. It would be big and heavy.
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