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120kv 10-20mA SMPS

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Fabi

Thu Aug 25 2011, 08:48PM

Registered Member #3510 Joined: Mon Dec 13 2010, 08:31AM
Location: western germany
Posts: 19

I will insert my Setup into oil. It isolates up to 12kV/mm.

btw. on the attachment you can see my setup.

Linas

Thu Aug 25 2011, 09:00PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

well, idea is same as mine right now, just i will use one primary and 7x20KV transformers on single core, and will have at least 240kV insulation between core and windings and around 120kv between core and primary.
just a heads up, you will have high voltage difference between primary and secondary, if you use 6 transformer in parallel, and if that is FBT from TV, it will be killed instantly

Fabi

Thu Aug 25 2011, 09:07PM

Registered Member #3510 Joined: Mon Dec 13 2010, 08:31AM
Location: western germany
Posts: 19

No I won't use flybacks.

I've got parts and the schematic from an other x-ray device.
So all these parts were used togeter in a C-arm for 110 kV 10mA continuously.
Those transformera have layer-insulation and are inserted in oil too

Linas

Thu Aug 25 2011, 09:14PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Today i tested my idea of HV transformer.
i used simple secondary with no insulation ( well, distance is insulator here ) and i was able to get around 10-15kv.
so by using 2x more thicker wire (2x thicker insulation) and epoxy in between, i should get 120KV with no problems.
right now making files for laser cuter, and Monday i should have secondary ready for windings (wire is 0,18mm)
after that, it will be filled with epoxy, and that is end of story.
but now i need diodes for that.
i don't have enough BYV26E for that, and also solder 500 old ones is quite hard.
i need 4x160KV 40mA 50-100ns diodes, i can trade it for my old HV tube or water cooled diffraction tubes
what are disadvantages of connecting diodes in series and then in parallel ?
( for each string i will use 500-1k resistor for balancing)

Fabi

Sun Aug 28 2011, 04:46PM

Registered Member #3510 Joined: Mon Dec 13 2010, 08:31AM
Location: western germany
Posts: 19

I think that parallel diodes aren't quite a good idea (because of the tolerances)

If one diode gets warm/hot (and this will happen) then you'll get a kind of avalanche-effect or chain-reaction.

If you're wnat to be on the safer side, use higer current approx. 40mA (Anode current) rated diodes.

If you're "crazy" build a vacuum-tube rectifier. But it will bring some problems

...

Linas

Sun Aug 28 2011, 05:35PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

well, i need at lest 10x in parallel to stand continuous current, and because it's full wave rectifier, 20mA output give just 10mA on string, mean that diodes will operate at 50% max average power, and one string can stand 10x rated power for shot amount of time.
where is no way any diode will get hot, not even warm.
idea right now use 16 in parallel, that will give peak power 5x more than single 40mA diode from ebay
and just 20% CW rated power
that sounds good, but also it at least 8-12h soldering

Adam Munich

Sun Aug 28 2011, 08:50PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

It doesn't matter how many you //. The one with the lowest forward voltage will explode, then the next one will explode... and the next...

...until there are no more diodes.

Fabi

Sun Aug 28 2011, 11:01PM

Registered Member #3510 Joined: Mon Dec 13 2010, 08:31AM
Location: western germany
Posts: 19

It doesn't matter how many you //. The one with the lowest forward voltage will explode, then the next one will explode... and the next...

...until there are no more diodes.

exactly.

The forward current of a single diode has to be even or greater than the anode/tube current...

Linas

Mon Aug 29 2011, 05:13PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Hell, i was so busy for making calculations for my transformer that i forgot that i have limited space, and now transformer can fit with no place for rectifier, that's sucks

anyway, all i have to do make bigger box for CT scanner, and that will cost 30$ again

and here is part for HV transformer, it looks quite big right now

Adam Munich

Mon Aug 29 2011, 05:15PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Use pvc cement to bond the plexiglass

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