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Rectifier progress

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LAN_403

Ash Small

Sat Jun 11 2011, 03:14PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'm starting to make a bit more progress on my rectifier now, which will be used for mains rectification for my HV H-bridge project. I'll also be using it for DC TIG welding and electro-polishing/electro-chemical processing (I blew my last one up TIG welding)

I've had these 300 Amp (average), 1200 Volt diodes for a while now:

(A bit on the 'overkill' side, but over-engineered is better than under-engineered)

Data sheet here:

and I picked up 26 brand new, unused 120 mm (~5") 47 CFM, 28 dB PC fans this morning that I scored on Ebay for Â£7.50 the lot! (they normally sell for around Â£5 each) part number D12SL-12 (Yate Loon).

Review here:

I'll only be using eight for the rectifier (two for each diode) so I have 18 spare for other projects.

I'm just waiting until I finish some smaller transistor heatsinks before I start on the four BIG heatsinks for this project.

Once the rectifier is finished I'll be starting on the gate driver for the H-bridge itself.

(I'll start a 'project' thread once I've made a bit more progress)

EDIT: I've also got some pretty encouraging results from preliminary tests for fabricated segmented coil formers for the HV transformer, using CD cases (which are made from clear polystyrene) and polystyrene cement:

EDIT EDIT: Some CD cases, which tend to be 'cloudy' or coloured, and which are more flexible, are polypropylene based, but the clear, more brittle ones are polystyrene, which, although not exceptional, does have pretty good insulation/dielectric properties. The polystyrene cement effectively 'welds' it together, thus producing a solid polystyrene bobbin, at least, that's the theory, anyway.)

Nah

Sat Jun 11 2011, 06:19PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Ash, what thappened to the homemade meter thing?

Paul

Ash Small

Sat Jun 11 2011, 06:50PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Nah wrote ...

Ash, what thappened to the homemade meter thing?

Paul

The best magnets I've found so far (of the shape and size I want) are N38, I'm looking for some stronger ones, preferably N52, but N4x wiil be better than N38.

If I've not found any better ones by next week I'll order Â£40 worth of the N38.

I'm planning on using either carbon fibre or graphite pivots. The rest of the design is pretty much finalised.

I've been reading the book that PM linked to on VTVM's, it's fascinating. I'll probably incorporate some VT technology into it eventually.

I only started that project as a challenge, for a bit of fun, and I don't want to stop work on my other projects while I'm working on it, but it has become quite interesting.

I was after eight identical 120 mm fans for my rectifier project and the ones I picked up this morning are exactly what I wanted at a very good price. I do have a few other projects underway as well as the moving coil meter. (RF and microwave ion source/plasma projects, mostly).

I should be posting some more progress on the meter project within the next couple of weeks.

Nah

Sat Jun 11 2011, 11:15PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

I could sell you a vtvm kit.

I bought an eico 221 vtvm, and took it apart, and repainted it and polished it. However, I never had the time it put it back together. It just needs a cap or two, and a 6SN7 tube, a common one.

Ash Small

Sat Jun 11 2011, 11:34PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Nah wrote ...

I could sell you a vtvm kit.

I bought an eico 221 vtvm, and took it apart, and repainted it and polished it. However, I never had the time it put it back together. It just needs a cap or two, and a 6SN7 tube, a common one.

I'll certainly consider it, Paul.

I've downloaded the manual and schematic. I was planning to start from scratch, but a lot of the parts should come in useful.

Any idea what shipping would be to UK, and how much you want for it?

Nah

Sun Jun 12 2011, 03:38AM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

ash,

Could you give me your address?

PM me and we'll work something out

Ash Small

Wed Jun 22 2011, 11:30PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

As I was given a quote today of nearly Â£1,000 for necessary welding on my truck, it looks like I may well be finishing my Mk II rectifier sooner than expected, so that I can do the welding myself.

I'm also looking at a 500 mile round trip to collect the rest of my TIG welding kit, which went into storage when I moved house last year.

The alternative is paying someone else to do the welding, or hiring/buying a MIG welder, so I figure now is the time to get my TIG welder 'up and running' again.

I'll still need to obtain some more aluminium for the heatsinks for the rectifier diodes, and fabricate them, which is a pretty labour intensive process.

It will also mean getting some argon, so I'll also be able to start doing some of the plasma experiments that I've been planning.

I'll also be able to post more details about my HF TIG welder, which I built before the days of 4HV.

Unfortunalely, I may have to put other projects 'on hold' for a few weeks.

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