PWM'ing thousands of amps - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: February 23, 2024, 02:52:56 pm
content: Hi,I know this is common activity widespread all over the place, and no industrial secret, so if you have say a 10V battery, and you want 10kA's through a 1 milliohm load, (for 100ms) you turn an IGBT on and thats that.But say you want 5000A's (on average) from the same battery and load, do you then like to simply PWM the IGBT on and off at a frequency of a 1kHz or so?(Add inductive filters to stop the di/dt being so high etc etc)

author: Andy Chee
author_rank: Super Contributor
timestamp: February 23, 2024, 04:15:01 pm
content: Maybe on a related note, I've always wondered what the power supply of an aluminum smelter looks like (5V DC @ 200kA).I doubt they use PWM or any fancy switch mode voltage regulation, they probably just switch taps on a giant transformer or something.But the diodes must surely beefy monsters! And what did they use for rectification before semiconductors? Did they make mercury arc rectifiers that big?

author: Faringdon
author_rank: Super Contributor
timestamp: February 23, 2024, 07:36:04 pm
content: Thanks, we are making an RF jammer, so we need to switch thousands of amps on and off.The load is just the very low inductance coil, which has say a milliOhm of resistance.Sometimes we just want to switch on and pulse the load for say 100ms with 14000 Amps or so.The device is also believed to be useful in activating (or indeed deactivating) land mines.A friend of mine built one in his garage...used to just pulse away from a big cap bank.When i worked in the security cash box industry we made such a 14000 Amp pulse power supply in a few weeks. We were seeing if it would "gouge" the internal electronicsand open the cash box. So i know this sort of thing is very very common. What say you to a spot of PWM with a 5000 Amps source?....you know, turning it on and off with a duty cycle so you get on average 2500 Amps.

author: Zero999
author_rank: Super Contributor
timestamp: February 23, 2024, 08:16:41 pm
content: Is that even legal? I thought radio jamming was against the law.Why not use a super capacitor and a coil?Does this have to be reusable or is it a single use item?

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2024, 08:23:54 pm
content: Whoops! Fire that up anywhere remotely near anyone important and OFCOM can throw you in jail for two years, and/or fine you so much you'll be paying it off for the next fifty years. If the lads with no sense of humour from three letter agencies take an interest and decide its terrorism related, your future will be even worse, with the possibility of being handed over to the yanks to throw into gitmo!The only thing that's going to save your ass, is that I doubt you are competent to build a circuit to pulse even 100A well enough not to meltdown within a few milliseconds of first power up!

author: Gyro
author_rank: Super Contributor
timestamp: February 23, 2024, 08:37:47 pm
content: Yay, it's the weekend again.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 23, 2024, 08:54:14 pm
content: This is as real as the billions he made importing and selling cheap stuff made in China. That was just a few years ago. Is this why his "client" requires him to have a business name?

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2024, 09:03:05 pm
content: Doesn't have to be real, just a realistic threat. The donut knows all, the donut monitors all!

author: tggzzz
author_rank: Super Contributor
timestamp: February 23, 2024, 09:06:48 pm
content: Quote from: Ian.M on February 23, 2024, 08:23:54 pmSush.'Nuff said.

author: tggzzz
author_rank: Super Contributor
timestamp: February 23, 2024, 09:09:57 pm
content: Quote from: Faringdon on February 23, 2024, 07:36:04 pmNoted, so he can't ease history and hide the evidenc e.Well, two posts to one of his threads ought to increase my "Thanks" count by two.

author: tggzzz
author_rank: Super Contributor
timestamp: February 23, 2024, 09:16:07 pm
content: Quote from: Faringdon on February 23, 2024, 07:36:04 pmThe world is believed to be flat, and aliens are believed to be kept in Area 51, and my uncle believed he was Edward IX.The first time I personally saw the military investigating clearing land mines was in 1983, after the Falklands. If this concept worked it woul have been invented many many times.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 23, 2024, 09:58:52 pm
content: Sounds like a new and improved "sticky grenade":https://military-history.fandom.com/wiki/Sticky_bomb

author: Zero999
author_rank: Super Contributor
timestamp: February 23, 2024, 10:59:46 pm
content: https://www.wikihow.com/Build-an-EMP-Generator

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 24, 2024, 01:02:57 pm
content: It doesn't sound so much as a radio jammer (although it can certainly do that as a side effect), more like a lightning EMP simulator.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 24, 2024, 01:47:36 pm
content: Quote from: NiHaoMike on February 24, 2024, 01:02:57 pmNah, not at this low dI/dt. Magnetic field if that. I suppose it could pull steel parts out of place, and induce enough voltage to cause problems with wiring or low-level circuitry.Static discharge into a loop or bowtie antenna delivers considerably more EMP -- and that's just standard ESD testing. Do that with a Marx generator and you've got something truly offensive.Quote from: Andy Chee on February 23, 2024, 04:15:01 pmTap changers, maybe; they're normally sited near hydro so the supply may be quite stable anyway. Would imagine they use 12-pulse rectifiers or even more, with whatever they can for rectification. Voltage isn't that bad, recall they use whole chains of them in series. Anything from mercury arc to synchronous (brushed) or motor-generator sets would do, back then. May be regular semiconductors nowadays, just enough puck-style parts in parallel to do the job.Inductance is easy to come by at those currents; it probably acts as a choke-input rectifier (RL load, really) without any special treatment (e.g. loops of bus bar). Core materials wouldn't do much, as field strength at the conductor surface is already ca. 100kA/m, and a mu_eff around 10 is already pretty much saturated. Ripple with a 6N-pulse rectifier will be quite high frequency (6N * mains) and low in amplitude to begin with, anyway.Tim

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 24, 2024, 01:59:25 pm
content: They used mercury arc rectifiers.

author: jonpaul
author_rank: Super Contributor
timestamp: February 25, 2024, 01:00:10 pm
content: "I know this is common activity widespread all over the place"Tipoff ... .just another FTTS clickbait, no project, no goal except to waster time.j

author: Jeroen3
author_rank: Super Contributor
timestamp: February 25, 2024, 02:41:00 pm
content: Quote from: jonpaul on February 25, 2024, 01:00:10 pm* OP identity notice *

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 25, 2024, 03:45:17 pm
content: Quote from: jonpaul on February 25, 2024, 01:00:10 pmSeems like half the posts I see by you are in these very threads; you aren't adding any value here, and only making things worse for yourself and others. You can stop seeing them in your feed, you know?Tim

author: Zero999
author_rank: Super Contributor
timestamp: February 25, 2024, 05:42:13 pm
content: Quote from: T3sl4co1l on February 25, 2024, 03:45:17 pmI think many people reply to these threads because the original poster likes every post. It's appears to be a very effective tactic because he's never short of replies, whether they're useful or otherwise. I don't know whether it's attention seeking, some of it probably is, but there are occasionally some interesting questions.Regarding RF jamming: yes, active jamming is, but building a Faraday cage around a building, to effectively jam cellular phones inside is perfectly legal.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 25, 2024, 06:37:39 pm
content: Quote from: Zero999 on February 23, 2024, 10:59:46 pmThis is an EM P generator.https://en.wikipedia.org/wiki/ATLAS-I

author: Zero999
author_rank: Super Contributor
timestamp: February 25, 2024, 07:42:10 pm
content: Quote from: ahbushnell on February 25, 2024, 06:37:39 pmI had fun reading that article, but it's a bit out of the original poster's budget. It's a shame photonicinduction (a YouTuber who used to blow things up with high voltage) appears to be no longer active. I'm sure he would love this. Perhaps the original poster should contact him?

author: Ian.M
author_rank: Super Contributor
timestamp: February 25, 2024, 08:01:09 pm
content: Quote from: Zero999 on February 25, 2024, 07:42:10 pmWhat has Photonicinduction done to you to deserve *THAT*?

author: coppercone2
author_rank: Super Contributor
timestamp: February 25, 2024, 08:15:42 pm
content: This was caused by an overload in the meson acceleration coil. There is another coil in Pod 2, which you must pass to get to the bridge of the Rickenbacker. If you approach it, the same will happen there. But I have conceived a way to avoid this. Proceed to Engine Nacelle B. There I will provide you the benefits of my omniscience.

author: Faringdon
author_rank: Super Contributor
timestamp: February 26, 2024, 10:17:18 am
content: Thanks, For a single non-isolated, high frequency (eg >500Hz) SMPS, what is the highest current they tend to go up to?How do they manage the ripple current and switching node for those converters?Also, what are the likely switching frequencies for eg a 1000-15000 Amp , single stage SMPS?Also, what type of inductor cores do they use?And also, what kind of noise mitigation measures do they take?For example, a 4000 Amp SMPS, done with a single stage (no paralleling)......what kind of resistance do they get in the inductor?I can't imagine say 1 milliOhm of resistance in such a thing being achievable?.(eg say if it was a PWM Bridge controlled resistive load, with filter inductor.)There are no pictures of these kind of things on the web. Someone gave me a doc, but no real specifics. No detailed circuit diagram or BOM. No pictures.No scope shots.I guess this stuff is deep industrial secret?The following is just called a "rectifier"...so it just rectifys 3 phase?...not an SMPShttps://youtu.be/rjl8Q8WhiTAI am doubtful there are many high frequency SMPS's which do 1000Amp in a single stage?

author: Harrow
author_rank: Regular Contributor
timestamp: February 28, 2024, 12:13:40 pm
content: I visited an aluminium smelter once. The main supply busbar was sitting at waist height and you could walk right up to it and place your hand on it while it was live....amazing. It was something like 2ft x 2ft in cross-section. Oh, and we had to take our watches off before we entered the potlines, otherwise they'd never work again after the internal mechanisms got magnetised. I was also told they could only drive diesel vehicles into the potline hall as the engines for petrol vehicles would stop because the coil would saturate and wouldn't reliably create a spark...something like that.The other interesting thing was the elimination of metal loops in certain areas....all the handrails had non-conductive breaks in them, etc.

author: jonpaul
author_rank: Super Contributor
timestamp: February 28, 2024, 07:07:39 pm
content: FTSS bravo for the imaginaton.Go to LLNL, LBL, CERN, ITER, Fermilab and SLAC.Many fine papers and info on pulksed magnets, beam deflection and thermonuclear experiment coil drivers, with accurate current control, shaped pulses at 1000s to 100,000s A.just onehttps://nationalmaglab.org/user-facilities/pulsed-field/Have fun!j

author: gnif
author_rank: Unknown
timestamp: March 01, 2024, 09:04:36 am
content: QuoteLocked, seehttps://www.eevblog.com/forum/work-wanted/wish-to-setup-a-workshop-building-drones/msg5365403/#msg5365403