Continuum

[Kizmo]

Multi kJ over 100m/s disk launching from 2015-2016





It has been a wild ride over these years. I was clearing old junk from my hobby corner and came up with my induction launcher coils and disks.

Looking at my old posts at the 4hv im second guessing myself


Last build was limited by ESR and voltage of electrolytics, SCR switching as well as coupling between coil and the disk. Maybe we should remove all of these limitations?

[Kizmo]

Junkyard AC capacitors, total of 1100 µF at 3300 VAC. Should take 5 to 10 kV DC without too much problems.

In past i have even shrunk coins with similar capacitors without any trouble.

[Mads Barnkob]

Great to see you back at posting Kizmo! I only waited 5 years

What does the test voltage say about those AC output/PFC capacitors? Some AC capacitors have T-T and T-C test voltage ratings for 60 seconds specified.

[Kizmo]

It has been a while indeed.

I know very little about these capacitors.

The grey one is

TPC
BATCM286A
3 x 80 µF
Un 3,3 kV
Utc 10 kVrms

Stainless steel ones are

Montena
CDAR8210
3 x 80 µF
Un 3,3 kV
Ut 4,1 kV
Ui 10 kV

Montena
CDAR0239
3x 210 µF
Un 2,3 kV
Ut 2,9 kV
Ui 10 kV


I know someone who works with AC capacitors like these and he told me that their internal R&D DC testing voltage was 4,3 times the rated Vrms for 10 minutes.

I will have them in parallel and see what happens. Would love to be able to get around 8kV DC.

Failure can be violent due to the parallel connection though... face shield and protective clothing is must have.

[klugesmith]

Good to see you, Kizmo.

On last point, I guess it's like using microwave oven capacitors far above their voltage ratings.
Hobbyists probe the margins in products made to serve safely for many years.
Literally millions of capacitor-years for your type. Billions for MO capacitors.

[davekni]

I've heard that line-frequency capacitors such as these last about 100-150 shots of coin-shrinking before failure.  That may be plenty depending on your planned use.