What could i possibly do with these huge transformers? - Page 1
Forum section: electronics / general

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: November 25, 2018, 09:20:35 pm
content: Hey all!There was a lab liquidation about 6 months ago and i purchased a bunch of transformers and other electronics things. Since this was a auction they packaged everything in large quantities so i ended up buying two pallets of transformers and coils. I ended up giving half to my friends and to a local hackspace.I did however keep more than enough transformers to last a life time and two of witch are the beasts in the images below!What can i possibly do with these?They way ~50Kg are 3 phase and can handle 23.1A on the secondary, i dont have 3-phase power at home and it would probably just blow the fuseId love some suggestions!I added an iPod classic as a reference

author: capt bullshot
author_rank: Super Contributor
timestamp: November 25, 2018, 09:29:11 pm
content: That makes a rather compact boat anchor. All the mass concentrated in one piece of iron and copper

author: DC1MC
author_rank: Super Contributor
timestamp: November 25, 2018, 09:35:11 pm
content: With a bit of electrickery* in shuffling the coils you can make a really excellent separation transformer for the monophasic mains.Cheers,DC1MC* = You really have to know what you're doing, or find somebody who does.

author: Ian.M
author_rank: Super Contributor
timestamp: November 25, 2018, 09:39:34 pm
content: Carefully dremel off the winding on the center leg (to preserve the bobbin) and build the *ultimate* DIY spot welder?

author: IanB
author_rank: Super Contributor
timestamp: November 25, 2018, 10:10:36 pm
content: Before destroying anything, see if it can be dismantled? If you undo the bolts, can the laminations be separated and the bobbins removed, or are they stuck together with resin?I am guessing from the 380 V windings that Sweden has 220 V mains? (380 / sqrt(3) = 220)If you were to apply 220 V mains to any of the 380 V primaries individually it should be fine and should blow no fuses (except for startup current) unless you draw too much power from a secondary.So then you would have a nice former to wind your own secondary onto. You could get high current, low voltage for spot welding or stick welding. Or other voltages for whatever purpose.

author: Brumby
author_rank: Unknown
timestamp: November 26, 2018, 12:14:11 am
content: Quote from: IanB on November 25, 2018, 10:10:36 pmThis would be the biggest issue in using it as is. I would recommend using a multi stage power up procedure where you would switch in increasingly higher powered resistive loads (such as incandescent light globes) connected in series with the primary to get the magnetising current going. The final stage would be to short out these loads so that the transformer is directly connected to the mains.On second thought, for the power this thing can handle, I would probably not use light globes. A couple of bar heater elements would be better.

author: Cyberdragon
author_rank: Super Contributor
timestamp: November 26, 2018, 08:41:40 am
content: Nah, it's only 20 amps, no fancy switching needed. Just get some 35-50 amp thermistors (Ametherm has some good ones).

author: Berni
author_rank: Super Contributor
timestamp: November 26, 2018, 09:03:24 am
content: You can use it as a single phase transformer by hooking up only the center winding and ignoring the two on the sides. It turns it into a normal E core transformer. You could also hook up to both the other coils on the sides in parallel to get a 1:1 isolation transformer.As for the inrush current yes you will likely want a soft start on something this large. Connecting it to the mains with a few kW heating element in series should start it up nicely, once its running you bypass the heater to connect it directly.For disassembly it probably wont fall apart if you take out the bolts because from the first photo it looks like it was varnish dipped.(Tho if it was not hot dipped or vacuum impregnated then you might be still able to get it apart with some force)Another use for it is wrapping a few turns of thick copper wire around one of the legs to make a welding transformer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 26, 2018, 09:16:36 am
content: Would be fine for a power-anything that needs 6kVA behind it. Audio amp (at this power, more like mechanical shaker table or stadium PA), VFD, welder, induction heater, powerful bench supply... or just wired for lower voltage mains circuits (the transformer should be enclosed in a metal box like this,https://www.alfatransformer.com/images/dry_type_transformer_header_image.pngfor a fixed-wired facility installation).Otherwise -- eBay. Should be able to get a little above shipping cost for it. List price of new transformers that size is a few hundred bucks; though you may not be able to find a buyer that will pay as-new for the oddball voltage (and/or without an enclosure).Tim

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 26, 2018, 09:20:12 am
content: Set up a magnet motor and use this to feed your free energy into the Grid.Seriously, I'd advertise on Ebay and various other websites. There may well be industrial buyers.

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: November 26, 2018, 12:19:59 pm
content: Quote from: IanMacdonald on November 26, 2018, 09:20:12 amQuote from: T3sl4co1l on November 26, 2018, 09:16:36 amI did pay 500SEK ($55USD) for the two pallets so I could sell them, it just feels like a waste to not build something cool out of themHow much would these two be worth to the right/wrong seller? I have no idea what big transformers go for...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 26, 2018, 02:10:16 pm
content: Oops, misread the label somehow, edited to reflect that.If you aren't intent on building some kind of project like the sorts of things I listed, then you can list it on eBay with, say, a reserve of $100-200 equivalent, maybe. Don't forget to calculate realistic shipping to whatever area you're selling it to!Tim

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: November 26, 2018, 03:11:28 pm
content: Quote from: T3sl4co1l on November 26, 2018, 02:10:16 pmIt would be amazing to build a powerful audio amp, I’m not an audio file myself but it’s always nice learning some new tricks! Do you have any recommendations?

author: capt bullshot
author_rank: Super Contributor
timestamp: November 26, 2018, 03:23:35 pm
content: Quote from: Sudo_apt-get_install_yum on November 26, 2018, 03:11:28 pmThat's not a high end audio amp, but here's a way to build something from components just for the purpose of using the components. This transformer would make a nice power supply for an extended version:http://wunderkis.de/pwramp3/index.html

author: Berni
author_rank: Super Contributor
timestamp: November 26, 2018, 03:41:17 pm
content: Quote from: capt bullshot on November 26, 2018, 03:23:35 pmNow that is quite the beast of an output transistor and i can certainly see how getting it to work involved a lot of analog headaches. I also wonder how much power will it survive given that the SOA is not specified for DC, these modules are usually built from many smaller transistors inside and love to get into thermal runaway.The voltage sounds about right for a high power amplifier at 150V. This gives you about 210V once rectified so a split supply with that could proabobly generate 400Vpp on the output and that works out to about 140V RMS. Putting that across a 4 Ohm load gives 4.9kW for a sine wave. This being a 6 KVA transformer makes it perfect.I have recently built a 1kW amplifier with +/-150V supply rails, it gets about DC to 600KHz of bandwidth. But it was designed to drive sonar transducers (Hence the high voltage and bandwidth) so its built to operate on a very short duty cycle. The small poorly cooled output transistors would quickly blow up if one tried to get 1kW continuous out of it.

author: r0d3z1
author_rank: Regular Contributor
timestamp: November 26, 2018, 03:48:16 pm
content: you can use it as inductive load to test your motor control board

author: capt bullshot
author_rank: Super Contributor
timestamp: November 26, 2018, 03:58:46 pm
content: Quote from: Berni on November 26, 2018, 03:41:17 pmI tried to open a module, but it is potted the hard way. It has a 1kW power dissipation, and I managed to break a module in that amplifier by running max. output current into a short. For sure, that module broke down due to too high junction temperature, but it took a while, so I don't think of internal thermal runaway but rather general overheating due to insufficient thermal sinking. The datasheet specifies some kind of SOA that covers the whole power dissipation at any combination of voltage / current as far as I remember. These old style modules are too old for the "many transistors" approach, I believe it's rather a single transistor die inside.Regarding your amp: 600kHz BW from 150V rails is impressive, too

author: coppercone2
author_rank: Super Contributor
timestamp: November 26, 2018, 05:48:01 pm
content: Use it as a isolation transformer for a nasty device you build that makes lots of noise. It will limit line surge to like 400a in a short vs the potential 2ka from the pole

author: duak
author_rank: Super Contributor
timestamp: November 26, 2018, 06:45:20 pm
content: I could have used something like that to operate some chinese machinery last year. Shipping it here would probably be too expensive.How about making a magnetizer/demagnetizer? If the core doesn't come apart easily then it would have to be cut to make a gap. I think diamond saw wire works.Cheers,

author: Berni
author_rank: Super Contributor
timestamp: November 26, 2018, 08:25:12 pm
content: Quote from: capt bullshot on November 26, 2018, 03:58:46 pmIts also possible that it handles linear operation better just due to being a BJT. Its the modern MOSFETS with low Rdson and IGBTs that are the most famous for developing hotspots in the die and blowing up under extended periods of linear operation.And yes getting this much bandwidth from it has involved a lot of hair pulling. My first attempt was a BJT output stage design, but at the required currents they simply would not switch fast enough. Many many hours in LT Spice later resulted in a redesign of the whole thing and the use of a MOSFET output stage. It used low gate charge high voltage FETs and a strong gate drive circuitry to make sure it switches fast enough. All in all it ended up being made out of about 30 transistors. The gain stages, current sources, bias generation and gate drive was done with BJT transistors as they are fast enough at low currents. A few more transistors are used to switch the amplifier between standby and active within a few microseconds(Standby reduces power use to near nothing and also floats the output to eliminate the need for a Transmitt/Recieve switch later on)The damn thing loved to oscillate in weird ways with all of that bandwidth. With certain loads at certain output power it would become a 400 MHz oscillator with significant output power even. I would never believe that a big power MOSFET can output a signal this fast. This particular oscillation turned out to be a LC circuit formed by the internal structure and tough hole pins of the MOSFET itself. Adding damping capacitors and ferrites in the right places calmed things down as well as putting ferrite rings on pins of MOSFETs. More LT Spice, cursing, some electrical shocks and exploded components later and eventually the thing was stable with all sorts of loads(Even heavily capacitive or heavily inductive and surviving dead shorts) and worked perfectly.The resulting powerful output of the amplifier once ended up driving a pocketwatch sized lump of piezoelectric element so hard it exploded from the mechanical stresses.

author: Brumby
author_rank: Unknown
timestamp: November 27, 2018, 01:55:23 am
content: QuoteI know just the person to ask....https://www.youtube.com/user/Photonvids(Anybody know how he's going?)

author: MrMobodies
author_rank: Super Contributor
timestamp: November 27, 2018, 02:00:41 am
content: Oh yes the mad electrician.He does a lot of creative things.Look at the washing machine that went bezerk and fell apart when he threw a brick in it.

author: Berni
author_rank: Super Contributor
timestamp: November 27, 2018, 06:41:44 am
content: Ah yes good ol PhotonicInductionHe did have some trouble with other aspects of life lately, no idea what he is up to now. The channel doesn't have all of his videos, he deleted his youtube channel at one point too. Tho these days with the youtube bots taking down videos for stupid reasons, im sure those bots would have a real field day on his videos since nearly all of them involve fire at some point.I know his videos are not exactly creative but it was fun to see various things "cranked up until they pop".

author: GeoffreyF
author_rank: Regular Contributor
timestamp: November 27, 2018, 01:55:19 pm
content: Connect the secondary as the primary, build an interesting 3 phase cockcroft-walton ladder. Of course the voltages would be well past lethal. Think of the Jacobs ladder exhibit or all the things you could ionize (including yourself)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 27, 2018, 02:11:42 pm
content: Quote from: Sudo_apt-get_install_yum on November 26, 2018, 12:19:59 pmYou could probably at least break even on the scrap copper - shouldn't be hard to extract with an angle grinder.

author: Berni
author_rank: Super Contributor
timestamp: November 27, 2018, 05:47:10 pm
content: Quote from: GeoffreyF on November 27, 2018, 01:55:19 pmI wouldn't recommend doing that in the UK. Would be fine in the USA tho.The magnetic field strength in transformers is designed to be pretty close to the saturation of the magnet laminate steel core when run at rated voltage. This allows them to get away with less turns on the coils causing the transformer to have less resistive losses, be lighter and cheaper to make. This also means that if you try to run a lower voltage winding at a significantly higher voltage it causes the core run into saturation, this causes the inductance of the wingdings falls off a cliff, this causes the input current to sharply rise and trips the breakers.Good transformers for producing high voltage at high power are american pole pigs. They have a 110/220V secondary where you can feed your mains into and get a few kV out the high voltage side. They are not too common in 3 phase forms but you can wire 3 of them together into any 3 phase configuration.These pole pig transformers are much more difficult to find in Europe because here its more common to have one large distribution transformer turning 20 to 100 kV down to 230V. Unforcenetly these transformers weigh a few tones and have rated powers in the range of 100kVA to 50 MVA. The magnetizing current on one of these likely exceeds the capability of a typical 3 phase residential service (About 16 to 30A per phase), so even if you could somehow get one you wouldn't be able to turn it on without blowing fuses.

author: coppercone2
author_rank: Super Contributor
timestamp: November 27, 2018, 07:49:13 pm
content: Quote from: Berni on November 26, 2018, 08:25:12 pmdoes anyone else get anxiety imagining themselves having to deal with this?

author: capt bullshot
author_rank: Super Contributor
timestamp: November 27, 2018, 09:09:37 pm
content: Quote from: coppercone2 on November 27, 2018, 07:49:13 pmNo, why should I?Anyway, regarding pole pigs and European distribution transformers, one can acquire "Messwandler" (Potential Transformers) here (e.g. 10kV : 100V), these can make nice jacobs ladders too:http://wunderkis.de/britzel/index.htmlOr simply MOTs (microwave oven transformers), remember ElectroBoom nearly killing himself with one?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 28, 2018, 06:56:13 am
content: A friend has a potential transformer that's very modestly rated... the trick is, because they're intended to sense the potential very accurately, the coupling factor is very high. They're not intended for many VAs, but a high VA capacity is necessary and sufficient for their desired operation. Indeed, they have much lower leakage than a conventional type does, which makes them... very exciting indeed, for high voltage testing!In practical terms, it really just means you need a ballast on the primary side, and then you can use them for whatever you like.Needless to say, the friend has documented just how large of an arc you can get from a residential (US) feed, before the breaker opens the circuit.Tim

author: Berni
author_rank: Super Contributor
timestamp: November 28, 2018, 07:45:28 am
content: Quote from: coppercone2 on November 27, 2018, 07:49:13 pmOh don't worry it was not as violent as if the thing was full of gunpowder or something. It just made a bang and flew apart into chunks. I think most of the bang was due to the silver electrode plating vaporizing due drawing an arc.Most electronics that operate at above hundreds of watts are capable of making some spectacular failure modes that involve bangs, sparks or fire. Also 100V to 200V is a range where voltage is high enough to give you a decent shock, but still low enough that you are not terrified of getting close while running. For something operating at kilovolts at 100s of watts i would certainly not come close until i can see the plug is pulled and caps discharged as a shock there can quickly become deadly.Quote from: capt bullshot on November 27, 2018, 09:09:37 pmAh i didn't know about these measurement transformers. I could imagine something like that can output a good deal of power and transformers can usually be massively overloaded in terms of current for short periods as it takes time for all of that copper to warm up.Yeah MOTs are by far the easiest way to get into the 2kV range. I wouldn't be surprised if someone here of there manages to kill themselves while messing with one, we just don't hear about a lot of the cases.