Component questions

[lovelacetx]

I'm finally getting around to making a DRSSTC.

A while ago I purhcased some new snubber capacitor boards from Ebay. They are filled with some capacitors that I think are quite usable but I'm missing some important data and welcome any comments/suggestions.

1. Electronic Concepts, 5MP1/2 Series, Metallized Polypropylene, 5uF, 1000V, 900A peak


2. Hitachi, WMTB-P Series, Metallized Polypropylene, 1uF, 1200V, ?? peak current. I cannot find any peak current data. Any guess as to a reasonable value?


3. United Chemi-con, DFDA Series, 0.47uF, 1000V, ?? peak current, again a lack of data, any help here?


Finally, I also came across several new CM100DY-12H IGBT bricks. Can these devices be used reasonably well in a DRSSTC?
I'm placing a link here to the CM100DY-12H data sheet https://drive.google.com/file/d/1S4M61G2dM0PF5QNSRJjkG5tBogCfzLxx/view?usp=sharing

[Mads Barnkob]

Hi lovelacetx and welcome to HVF

Are you asking about those capacitors for MMC or snubber application in the DRSSTC? Without having looked at the datasheets my initial comment is that 1 has too high capacitance to make a reasonable MMC without using too many capacitors. 2 is the most fitting just from the capacitance. 3 is unfit from a very bad dissipation factor it will most likely die from heat sooner than the others.

The square/rounded or should we call them flat-rounded MKP capacitors are a older type of snubber capacitors with worse specifications than modern pulse MKP capacitors, so if you are just going to use them for inverter snubbering, use one 5uF and one 1uF in parallel for a wider range of snubbering.

From others experiences (see bottom table of following link), a CM100 would properly be good for 500A+ primary peak current, you can do the math with your dream operating parameters and see if the heat dissipation fits the desired resonant frequency: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

[lovelacetx]

Thanks for the feedback.

The snubber boards that I picked up for $8 each had 1x 5uF, 3x 1uF and 5x 0.47uF caps.



The 1uF caps look like good candidates for the MMC.

It looks like the CM100DY-12H IGBTs will work at 100kHz without a problem.

[Mads Barnkob]

I seem to recall that some of these "oval" film capacitors had a rather bad ESR rating, try and see if you can find a datasheet or some more information about them, maybe we can calculate the rest of the specifications if needed.

[T3sl4co1l]

Think I remember seeing EC caps in some induction heaters... maybe they were GE or something completely different, it's been a while.

Hey, they have an assembly diagram online!
http://www.ppstinc.com/download/25kW_HF_Spare_Parts_List.pdf
3-11 is a radial (screw mount!) cap that handles inverter supply ripple.  I think it was white, but maybe it was yellow...

3-18 is a big array of bypass caps, I think I still have a few laying around, GE 40L3221, 2.2uF 400V.  Good ripple, maybe not suitable for full wave resonant purposes though.

And yes, those are gate driver boards, screw mounted.  Don't get excited, they're little more than a driver chip on a board.  The whole machine is... very labor intensive.

May be cheap to find spares though, would be a good enough start for a fair sized coil.

Tim

[lovelacetx]

I can't find the exact data for these caps. The EC cap is a 5MP series, which is a very good cap, but at 5uF, too large to be useful in an MMC. The 1uF caps are Hitachi AIC
WMTB-P caps, but I can't find any meaningful data as I can for the Cornell Dubilier or EC caps.

So, I broke down and bought some CD 942C20P15K caps. Found them for ~$4.90 each (including tax and shipping) from TTI, not too bad compared prices I saw elsewhere.

[Mads Barnkob]

Hitachi AIC WMTB-P might be useful for a MMC, but we can not know for sure. It is a little weird that they brand it as a high frequency, high current capacitor for snubbers and give no data on it. Datasheet: https://4donline.ihs.com/images/VipMasterCap/Capacitor/HITJ/HITJS03140/HITJS03140-1.pdf

Maybe you can calculate some of the properties from their general film capacitor catalogue data: https://www.aic-components.com/app/download/14952484922/Plastic%20Film%20Katalog%202018%20EMail.pdf?t=1529920956

CDE942C capacitors are a legend in Tesla coiling, works fine for smaller DRSSTCs, but if you are going to need anywhere near 0.5uF or above, its starting to get too expensive and big GTO snubber capacitors is a cheaper alternative.