EBAY FS (Germany) : Medical Isolation transformers, 230V, 150VA, 54EUR - Page 1
Forum section: electronics / general

author: Falkra
author_rank: Regular Contributor
timestamp: August 04, 2016, 09:50:44 am
content: Hello,I recently bought two of these isolation transformers from this ebay seller (nitram39).Theye were like new, with original packaging, and shipped quickly.I posted the link in the latest purchase topic, and another forum member bought one.Here is the link :http://www.ebay.fr/itm/322215543868The seller already has sold 3, and his ebay sales are for two at a time.When two isolation transformers are sold, he sells 2 more, later, so the link changes but you can find them from the user name.3 attached pictures.Just for sharing, if anyone is interested. These are not my auctions/sales.54 Eur seems to be a good price (IMO), shipping was 12EUR (to Europe).

author: neslekkim
author_rank: Super Contributor
timestamp: August 04, 2016, 11:33:12 am
content: Oh.. hope he can ship to Norway also.. have asked so hopefully they aren't sold before I get an answer

author: Falkra
author_rank: Regular Contributor
timestamp: August 04, 2016, 12:31:00 pm
content: I hope you can get it.The seller didn't answer instantly but I got a good contact with him (in english... my german is very bad).Good luck, don't hesitate to post your feedback when you get the transormer, if everything is ok.

author: Falkra
author_rank: Regular Contributor
timestamp: August 04, 2016, 03:22:30 pm
content: I see both have been sold. I'll update the link in the first post if the seller has more.

author: neslekkim
author_rank: Super Contributor
timestamp: August 04, 2016, 06:44:57 pm
content: Quote from: Falkra on August 04, 2016, 03:22:30 pmHope they will work as expected

author: Falkra
author_rank: Regular Contributor
timestamp: August 04, 2016, 07:24:10 pm
content: I hope so.Mine were ok, like new.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 07, 2016, 05:04:40 pm
content: I messaged the seller and found that he does not have more of these, so if anyone thinks one is enough I'd like to buy the other one

author: Iwanushka
author_rank: Frequent Contributor
timestamp: August 07, 2016, 06:48:48 pm
content: Quote from: PA0PBZ on August 07, 2016, 05:04:40 pmLooking for one too!

author: HighVoltage
author_rank: Super Contributor
timestamp: August 07, 2016, 09:03:57 pm
content: What is so special about a "medical' insulation transformer?Just better quality and higher reliable transformer?

author: electr_peter
author_rank: Unknown
timestamp: August 07, 2016, 09:38:53 pm
content: Quote from: HighVoltage on August 07, 2016, 09:03:57 pmNothing too special - mostly quality and piece of mind. These medical tranformers in particular:have low leakage current (both input and output)have multiple protection from over-current/over-temperatureare insulation tested to 4kV AC RMShave shielding between input/output windingsIn other words, having this thing in one's lab should not increase risk of fire.Before usage as true isolation transformer, be aware of actual wiring inside:Input live/neutral is isolated from output live/neutral (obviously)Input/output earth is not connected to any winding (check to be sure, some medical transformers have output neutral and earth connected).Input earth is carried through to output earth (!!!) - one may have to take this into account in some situations or make modifications as needed. Having carried through earth may compromise "isolation" in some measurement situations.

author: neslekkim
author_rank: Super Contributor
timestamp: August 07, 2016, 09:59:08 pm
content: Quote from: electr_peter on August 07, 2016, 09:38:53 pmAre you saying that this one have earth carried throuhg?, or that one in general should check that on such transformers?For me the issue is the earth, want to use it on the occasions where I don't want to blow up the scopeMedical or not, that was not so big issue, the point was to finally get one that would isolate 230v - 230v..

author: Monkeh
author_rank: Super Contributor
timestamp: August 07, 2016, 10:19:32 pm
content: Quote from: electr_peter on August 07, 2016, 09:38:53 pmIf there is no earthed wire there is no neutral.

author: TopLoser
author_rank: Unknown
timestamp: August 07, 2016, 10:51:07 pm
content: "Output floating, Neutral not grounded"From pics on the first post.

author: Monkeh
author_rank: Super Contributor
timestamp: August 07, 2016, 10:53:41 pm
content: Quote from: TopLoser on August 07, 2016, 10:51:07 pmSadly even the manufacturers can't get simple terminology correct.

author: nctnico
author_rank: Super Contributor
timestamp: August 07, 2016, 10:54:19 pm
content: Quote from: neslekkim on August 07, 2016, 09:59:08 pmThe usage for a isolation transformer in medical equipment is (probably) to add some extra security in case one of the mains wires get lose and touches the casing (fire/shock hazard). Either way medical equipment is grounded using thick ground straps and most certainly not floating.Using an isolation transformer to float a circuit or test equipment is bad practise and should not be done because there are numerous way this can lead to potentially deadly situations without being obvious to the operator. People will probably disagree with this but then again there are those who say smoking isn't bad for your health.

author: electr_peter
author_rank: Unknown
timestamp: August 07, 2016, 11:12:35 pm
content: Quote from: neslekkim on August 07, 2016, 09:59:08 pmTo my knowledge, earth is carried though almost always. I consider carried earth default setup for any transformer unless stated otherwise. I strongly suggest to test for continuity on all isolation transformers before use - text labels and indications may be misleading.As to transformer in question, Noratel IMEDe150, see page 15 from manufacturer's brochureIMED medical PSUsAlso, as can be seen in picturesQuote from: TopLoser on August 07, 2016, 10:51:07 pmThus, my best guess is that input/output windings are completely isolated from earth. Earth itself is carried through.Anyway, I will have a real thing to test and use soon. I will make modification inside transformer or make special cable to break earth on output.Quote from: Monkeh on August 07, 2016, 10:19:32 pmTrue in literal term usage, but that is only nomenclature. "Neutral" can kill you, so why is it called "neutral"? I consider "neutral" equal to "live", because both comes from same transformer. Let's not go to linguistics of L vs N.I was referring more to IEC C13 and C14 plugs/sockets - these have small letters L/N/E on them. Letters allows to identify and name wires w.r.t. IEC socket/plug.My point is that these IEC connectors are "polarised" at least with naming convention L/N/E - irrespective of what is connected to actual pins.

author: electr_peter
author_rank: Unknown
timestamp: August 07, 2016, 11:43:25 pm
content: Quote from: nctnico on August 07, 2016, 10:54:19 pmI agree that isolation transformer can be very dangerous. But where does this "danger" comes from? It comes from the fact that isolated output may be connected to mains referenced circuit in some way (via oscilloscope GND, for example) making it not-isolated once again !!! User of isolation transformer must take this into acount.As mentioned, use of isolation transformer is considered a bad practise in cases when other methods are available. I personally use isolated HV probes for mains stuff.However, sometimes you need to have equipment 100% isolated from mains. For DC power one can use batteries, but for AC power the best solution is isolation transformer. And isolation transformer which carries earth through is only "half isolated" - that means isolation may or will be breached in some non-obvious way.You need fully isolated transformer - meaning no physical contact between any of L/N/E wires. Disconnecting output earth will guarantee this in above case."Earth" as such is meaningless term for single local isolated voltage source and single load. "Earth" wire that is not even connected to secondary winding (but connected to mains earth) has no business on output wiring for isolation purposes in a lab.

author: neslekkim
author_rank: Super Contributor
timestamp: August 08, 2016, 06:20:09 am
content: Quote from: electr_peter on August 07, 2016, 11:43:25 pmNot going to do mains stuff, but this kicked me off:

author: HighVoltage
author_rank: Super Contributor
timestamp: August 08, 2016, 08:47:33 am
content: Good explanation, guys!Thanks, that is what I expected.I have a huge 5 kW insulation transformer in my lab.It has the earth connected from the input to the outputBut line and neutral are floating.And yes, insulation transformers can be very dangerous.

author: Falkra
author_rank: Regular Contributor
timestamp: August 08, 2016, 04:03:13 pm
content: Hi, I'm not at home for 2 weeks, so I can't do some testing.Quote from: electr_peter on August 07, 2016, 11:12:35 pmI think you bought one, if I remember well. If you make any modifications, please show us in this topic, as it is always interesting stuff.

author: electr_peter
author_rank: Unknown
timestamp: August 09, 2016, 07:03:57 pm
content: Quote from: Falkra on August 08, 2016, 04:03:13 pmCheck my post hereteardown-and-modification-of-noratel-imed-e-150-isolation-transformer

author: Falkra
author_rank: Regular Contributor
timestamp: August 10, 2016, 07:27:39 am
content: Thanks, I will read !

author: neslekkim
author_rank: Super Contributor
timestamp: August 12, 2016, 07:54:08 pm
content: Got mine today, looks very good, thanks!

author: Falkra
author_rank: Regular Contributor
timestamp: August 13, 2016, 08:12:03 am
content: Great, have "fun".