Surprise package ! - Page 1
Forum section: electronics / general

author: Fryguy
author_rank: Regular Contributor
timestamp: June 27, 2013, 03:51:05 pm
content: A week ago i asked a friend if he's got some power diodes in his junkbox - all i wanted was a set of diodes to build a 10A+ bridge rectifier for a PSU powerstage . . .4 days later he called me and said he's got a set of power diodes for me - so i payed him a visit and he gave me 4 nice tiny diodes .Each one 22cm long , 32mm thick and weighing 250 g !They can handle up to 1200V and 500A . . .What am i supposed to do with that kind of hardware ?At this point i'm open for suggestions .I'll admit that i own a set of 4 450A power mosfets in one of my junkboxes - they should work nicely together with these diodes . . .

author: Unknown
author_rank: Unknown
timestamp: June 27, 2013, 03:57:08 pm
content: Make a bridge rectifier for photonicinduction?

author: SeanB
author_rank: Super Contributor
timestamp: June 27, 2013, 06:19:14 pm
content: Make a bridge out of them, you will not need a heatsink at 10A though those, just the case alone will do.

author: poorchava
author_rank: Super Contributor
timestamp: June 28, 2013, 06:22:06 am
content: Connect in parallel and short railway traction to groundOr one really huge inverter welder.

author: Unknown
author_rank: Unknown
timestamp: June 28, 2013, 06:26:34 am
content: 1200V at 500A... that's 300 megawatts?Or is it up to 1200V or 500A?

author: c4757p
author_rank: Super Contributor
timestamp: June 28, 2013, 06:30:09 am
content: Well, they are diodes... They're rated to either conduct 500A (at whatever VFis) or block 1200V. I suppose that means that they're rated for use in a maximum 300 MW circuit, but not dissipating 300 MW themselves!Out of curiosity, what is VFon a monster like that?

author: Unknown
author_rank: Unknown
timestamp: June 28, 2013, 06:41:01 am
content: Oh, that makes sense. That didn't sound right.Pardon the occasional stupidity, my mind has its fuzzy moments.

author: Kremmen
author_rank: Super Contributor
timestamp: June 28, 2013, 08:02:37 am
content: Quote from: Fryguy on June 27, 2013, 03:51:05 pmAh, brings back memories from way back when i was working with power electronics...Medium size diodes like these usually come in 2 varieties, at least those made by IR and Semikron do; one with anode in the body side and one with cathode. From the picture one can see that 1 of the diodes is the former. If you happen to have 2 each then it is very simple to build a robust rectifier by bolting 2 each to a heat sink and connect the cable ends to AC 2 and 2, thus creating an ordinary rect bridge. That is how it is always done and the gizmo will handle all of your rectification needs.Quote from: c4757p on June 28, 2013, 06:30:09 amJust the normal PN junction threshold; less than 2 V anyway, but usually something like 1.2 - 1.5V.These babies are simple to apply, just bolt them to a suitable heat sink. Not so the real high power devices where currents can exceed 5 kA. The semiconductor die inside the puck can be like 7 cm (nearly 3") in diameter and proper cooling requires compression between heat sink radiators of several tens of kN. I remember we spent quite some time to develop an easily assembled, properly isolated clamping system which didn't need sophisticated tooling on the plant floor. The biggest rectifiers we made using those were 500 kA continuous current. You can imagine the installations were nothing like ordinary electrical supply cabinets

author: peter.mitchell
author_rank: Super Contributor
timestamp: June 28, 2013, 08:33:29 am
content: use em on your car as jump leads, you'll never get it around the wrong way if you make a bridge!

author: miceuz
author_rank: Frequent Contributor
timestamp: June 28, 2013, 04:24:53 pm
content: We used those for a makeshift car battery charger

author: SeanB
author_rank: Super Contributor
timestamp: June 28, 2013, 08:47:47 pm
content: Kremmen, just how many Belleville washers did you use per stud and how many studs per package assembly.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 29, 2013, 12:45:45 pm
content: If you're going to build your own electric car, those diodes would work great in the charger.

author: Kremmen
author_rank: Super Contributor
timestamp: June 30, 2013, 06:51:38 am
content: Quote from: SeanB on June 28, 2013, 08:47:47 pmSorry, it was too long ago to remember exactly. But we did it with these conical washers that apparently are also called Belleville.The idea of the assembly was this:- there was a more or less symmetrical heat sink element on both sides of the semiconductor puck.- the halves were clamped using hardened steel bar yokes. At each end the yokes were joined by a tightening bolt going through holes drilled through the heat sinks, isloated using a custom cast Ryton sleeve to avoid short circuiting the assembly.- At the centerline between the heat sink and the steel yoke was a stack of these conical washers on each side.- also on the centerline was a tightening gauge screw. It measured the compression by a simple dial scale pressed on one of the yokes. When the washers were flattened by compression, the gauge screw bottomed at different points on the scale. There was a calibration chart showing what reading to aim for to get the desired compression. It wasn't terribly accurate but served well enough.If memory serves there were several washers on each side, say 6-8 but i cannot recall better after all this time.P.S. these assemblies were for individual diodes or thyristors. Those were then further combined into various types of bridges with 6, 12 or 36 thyristors, the latter in big cycloconverters. The basic module was (is) a 6 thyristor/diode unit, rack mounted in a cabinet with a big cooling fan on the roof. You can then stack these on top of each other like you do pizza box serves these days. Connect everything with heavy copper bus bars and you're done.

author: SeanB
author_rank: Super Contributor
timestamp: June 30, 2013, 10:14:58 am
content: I use 5/8 ones on a form fill and seal machine, they are used as springs in a blow mould and in a sealer assembly these, as they have a better fatigue life than springs and have a very short stroke on them as well. 48 per section in 4 stacks on the slides. Replacing them is rather expensive, as I have to special order them from my local bearing supplier, they are not a common stock item for them, but they do have a stock. Normally they lose tension and go flat after a few years in the sealer, so the new ones go in the form side and the old ones move to the heater for final finishing off. IIRC they were $10 each last time I did them.

author: Psi
author_rank: Super Contributor
timestamp: June 30, 2013, 10:25:29 am
content: Use them in your project but make a feature out of themMight be a little tricky if they are carrying 230V but yeah

author: G7PSK
author_rank: Super Contributor
timestamp: July 01, 2013, 02:40:37 pm
content: I had some diodes like that, I made a DC pack to go on a 350 amp oil cooled welder and then paired them up with an old spark gap HF generator for tig welding aluminium, have since sold the set up and replaced it with a modern tig set but it worked for me over about ten years.

author: lemmegraphdat
author_rank: Frequent Contributor
timestamp: July 01, 2013, 11:15:45 pm
content: Quote from: G7PSK on July 01, 2013, 02:40:37 pmHow did you cool the torch?

author: lewis
author_rank: Frequent Contributor
timestamp: July 01, 2013, 11:53:31 pm
content: Quote from: duskglow on June 28, 2013, 06:26:34 amWhere did 300MW come from?

author: Unknown
author_rank: Unknown
timestamp: July 01, 2013, 11:55:48 pm
content: Me not understanding the difference between reverse breakdown voltage and forward voltage.

author: c4757p
author_rank: Super Contributor
timestamp: July 01, 2013, 11:56:25 pm
content: Quote from: duskglow on July 01, 2013, 11:55:48 pmWell yes, but also, you squared the current. Power is VI, not VI2!600kW is still a shitload of power.

author: Unknown
author_rank: Unknown
timestamp: July 02, 2013, 12:07:33 am
content: Oh, I got ie and i squared r mixed up. Sigh.