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Example of Quality High Power HVPS

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LutzH

Fri Aug 07 2009, 09:31PM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

I just picked this FuG 30KV 55ma unit up on ebay, I just wanted to share a picture of the inside because they used clear silicon insulation potting.

This is interesting because now you can see all of the encapsulated components in the high voltage doubler in the output section, in addition the the HFHV 20KHz transformer which drives it. The transformers ferrite core has about an 2cm x 2cm cross section. This gives you an idea on how much power these things can handle!!! This transformer is quit a bit smaller than the 60KV one, which I am selling on ebay to finance this purchase, it closes on Sunday if you want it :)

One thing that is interesting about the circuit in this FuG HVPS is; the protective features in the multilier section. To review the overall supply works like this:

1. Input 480V is rectified to about 600VDC
2. It is inverted with a half bridge IGBT to about 300V at 20KHz
3. It is stepped up to a maximum of about 8KV at 20KHz by the big ferrite core transformer.
4. It is multiplied to 30KV max, and filtered.

Fore safety the multiplier diodes are doubled up for increased current, and surge resistance. Each one is actualy 4 diodes: consisting of 2 x ( 2 diodes in series) connected in parallel.

There are HV resistors in series with the VM capacitors, they rated so that they keep any current surge under the HV diodes single cycle surge rating. Last there is a final output resistor which does the same thing.

I just wanted to share this design, if anyone knows anything about the HV clear silicon encapsulating material I would be interested in learning more about it. This seems like cool stuff, maybe of use with Tesla coils etc. One cool thing about silicon HV grease is that it does not form conductive carbon if any arcing occurs. I am assuming that the same is true for this clear rubber product which may make it an ideal insulation for HV coils?

To close I am still working on the high power 50KV Hf transformer, I will share the progress and information as it becomes available. Thank you all for your help with this!!!

Aloha....Lutz

...

Fri Aug 07 2009, 10:02PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

That is a pretty nice power supply, and shows you how big a core is needed for a reliable 1.5kw supply fed from a half bridge

The clear stuff looks like ordinary silicone (probably the non-acidic variety), which I have found to work well as a hv potting compound, and used in several of my hv supplies (

and

) to pot the windings of the hv transformer. It also seems to hold up quite well to the ozone formed in the supply

MinorityCarrier

Sat Aug 08 2009, 12:45AM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

RTV12 is excellent for potting high voltage subassemblies and is relatively inexpensive.

One thing you MUST do however is degas it after mixing by putting the mixing pot in a vacuum chamber and run it down to sub 1-Torr vacuum for 20 minutes or so, before pouring into the subassembly casting. Failure to do this will leave entrapped gas (air) bubbles suspended in the liquid which lowers the dielectric strength (400V/mil).

LutzH

Sat Aug 08 2009, 12:49AM

Registered Member #1721 Joined: Sat Sept 27 2008, 08:44PM
Location:
Posts: 136

Thanks for the info on the silicone, yes I agree you would have to use an acid free version. Plus I hate the smell of that sh%^#. I do however just love the smell of fresh HV silicon rubber insulated wire, it has a nice pleasent, almond like smell, kind of like the new car smell, ya I know its probably toxic, but come on let me have my fun :)

One thing that this unit has me doing is, seriously re-considering the half bridge driver for HFHV work. I had pretty much given up on the half-bridge due to the lower voltage, and to be honest just following the herd so to say, because the FW H bridge was what everyone else was doing. Now however we have fast 1200V, and 1700V HUGE IGBT'S all over ebay.

The half-bridge does have some very attractive features, like simplified driver design, easyer and more compact construction etc. As far as the H bridge having a power advantage goes, I mean does it really matter? I mean, come on, where do you need this? When you can get a new 1200V double IGBT module, which can handle 200-600 amps for 50-60 bucks on ebay, where can you possibly need more power? Unless of course you own your very own electrical distribution substation, and you can pull more than 100,000 W from the line!!!

I have even seen factory finished IGBT driver boards suitable for a half bridge, go for about $60.00 So why not build a bullet proof, 100KW rated IGBT half-bridge, and let it idle along at 10-20 amps max, instead of a stressed H bridge, with thumbnail size units? At this level of de-rating it should last a lifetime, or at least as long as the electrolytic caps in the driver.

I may contact FuG to find out just which silicon product that they used. FuG in Germany goes way above and beyond, in terms of customer service, and in supporting its products. They emailed me the complete schematics on this unit, and even offered technical assistance in doing the 480V 3 phase, to 480V single phase conversion. I was honest with them from the start in letting them know that I am not a commercial user, or company ect. I tried the same thing with Spellman, and another US based manufacturer a while back,and they would not give me the time of day. Everything was "Propriatary and Confidential" Come on, the darn thing was almost 15 years old, I am sure half of China has reverse engineered it by now. Take Care....Lutz

kerver

Sat Aug 08 2009, 07:54AM

Registered Member #522 Joined: Thu Feb 15 2007, 01:04AM
Location: The Netherlands
Posts: 33

hello

Would you pleasu post the schematics

thanks man sg3535 circuits it looks great

Steve Conner

Sat Aug 08 2009, 10:13AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

LutzH wrote ...

So why not build a bullet proof, 100KW rated IGBT half-bridge, and let it idle along at 10-20 amps max, instead of a stressed H bridge, with thumbnail size units?

Switching losses.

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