Obtaining TIW certificates from Rubadue Wire company? - Page 1
Forum section: electronics / general

author: hanakp
author_rank: Regular Contributor
timestamp: April 30, 2023, 12:15:36 pm
content: I know it's a long shot, but I have to try...From time to time,I assist with design and/or debug of small SMPSfor medical, industrial, scientific or other specialised uses. In the consumer sector, transformer safety is usually accomplished with triple insulated wires (TIW) that conform to EN 60950. Last year, I noticed that american companyRubadue Wire offers some TIWsthat allegedly have medical (EN 60601) and laboratory (EN 61010) certificates. The important word here is "allegedly." We needed a copy of the certificate, otherwise local safety authorities wouldn't approve the SMPS. But when we tried to obtain them from Rubadue ortheir european distributor, their reaction can be only be described as stonewalling. Over the last 2 years, we tried this twice with prospective buyers, first with a small local company, now with an american multinational corporation that has >$500 million annual revenue. But... nothing, no answer. We even tried calling them, but the manager always seemed to be busy. All we got was one e-mail from the distributor with Rubadue product listing, then they stopped answering too. So my questions are:1. Do you happen to know whether Rubadue actually has the EN 61010 certificates? Or is it "first order 200 km of the wire and then maybe we can talk about making the certificate" type of deal? Alternatively, do you know somebody there who would be more... forthcoming with such information?2. Do you know about some other company that makes TIWs certified for EN 61010? My Google searches come up empty.Thanks!(I searched the forum and noticed that TIWs and their use are a bit touchy subject here. But my problem is regulatory and communication one, not technical one. We already practically verified that TIW would be an improvement that justifies the cost. And a few years back, when we asked Totoku for their EN 60950 TIW certificate, we got it the next day.)

author: hanakp
author_rank: Regular Contributor
timestamp: May 04, 2023, 06:05:41 pm
content: IDK whether it's just a concidence, but we finally got an answer from Rubadue. It was actually a quite complex discussion and I'm not at liberty to post it here. The main point is that currently it's not possible to certify TIWs according to EN 61010, the standard simply doesn't account for their existence. Rubadue doesn't lie about EN 61010 in their catalog, though. Becasue at least some (presumably american) testing institutes will rubber-stamp a subset of EN 61010 equipment if the TIWs have medical EN 60601 certificate. What subset exactly is not clear, but in my case it's also irrelevant: a local testing institute flatly rejected such possibility. If the TIW doesn't have actual EN 61010 certificate, they won't rubber-stamp the SMPS, end of the story.Oh well, I wanted to know, so now I know...

author: f4eru
author_rank: Super Contributor
timestamp: May 04, 2023, 08:34:58 pm
content: The 60601 is a norm for medical equipment or itßs subsystems, not really for materials used in it.It requires certain guarantees and conditions, especially on insulation.Material and part vendors often tout compliance, but what they in fact mean is rather:"we made all the checks, and have the documentation ready, so your product using our part will easily pass the checks concerning our part."

author: TimNJ
author_rank: Super Contributor
timestamp: May 05, 2023, 06:50:25 pm
content: That sounds about right. I think it's possible for a wire manufacturer to get an IEC60601-1 report since the requirementsarelisted in Annex L of IEC60601-1. On the other hand, Annex L of IEC60601-1 is exactly the same as Annex U of IEC60950-1, and UL2353 is derived directly from Annex U of IEC60950-1. So it looks a bit like this?A UL cert for TIW is tested to UL2353, so if it says "reinforced" on the cert, this should be "importable" to any other standard which uses UL2353/IEC6950-1 Annex U as a basis.https://iq.ulprospector.com/en/profile?e=209784https://iq.ul.com/ul/cert.aspx?ULID=102519990IEC61010 does not actually include the requirements (as noted) so there's not really a way to show compliance since the requirements are not there.

author: jonpaul
author_rank: Super Contributor
timestamp: May 06, 2023, 07:19:28 am
content: In many decades of PSU/EBU /PFC design, we never resorted to TIW, nor any litz.For SELV, Medical, and other high isolation V requirements, a split bobbin or conventional tape insulation (3M56) were most cost effective and available for production designs.Besides Rubidue, MWS and the Yougoslavian wire vendors can make anyting you need but at a MOQ, and cost/lead time penalty.Bon ChanceJon

author: TimNJ
author_rank: Super Contributor
timestamp: May 06, 2023, 12:17:37 pm
content: Quote from: jonpaul on May 06, 2023, 07:19:28 amI think this is outdated advice. Sure, it worked for you at some point in time. That does not mean that it is still sufficient in today’s world, with various new requirements on efficiency and so forth. TIW certainly has helped achieve higher power densities, especially in small switchmode transformers where margin tape thickness or other barriers constitute a relative large portion of the available winding window.If it is available to you and makes sense to use, use it. Same applies to litz. Depends where you are making it and in what quantities, but litz, TIW, and TIW litz are not speciality items these days. They have very wide usage, and at low cost. Probably Rubadue is dumb expensive because there’s not much option in the US, if you want to buy local. But plenty of options in Japan and China if you can source from them.

author: Faringdon
author_rank: Super Contributor
timestamp: May 07, 2023, 11:51:42 am
content: TIW?....tryed TEX-ELZ from Furukawa?Or TEX-E?I am sure that has certs.

author: jonpaul
author_rank: Super Contributor
timestamp: May 08, 2023, 08:36:31 am
content: Tim NJ: Many thanks for the intersting comments: " I think this is outdated advice. ....does not mean that it is still sufficient in today’s world, ..... small switchmode transformers ..tape thickness ... relative large portion of the available winding window.....Same applies to litz. "So, this thread and questions re TIWhave mixed two different issues:1/Use of Triple insulation wire for safety compliance P-S2/ Use of Litz wire.My experiences extended to work in recent times, 40 kHz to 500 kHz, resonant, double fwd, or other soft switching, power 20W ..750W for production SMPS/EBU/HF Soldering (Metcal)1/ Insulation: Our designs had passed compliance including medical equioment thru use of solid HF, HPTZ, HPN mgnet wire.The insulation barrier was 3M 56 tape one or several layers.We also used bobbins with split flanges or concentric double bobbins desinged for SELV or medical transformers.2/ Wire for HF use; We saw that Litz is costly and hard to terminate in production.we used:a/ bunched wire (several smaller solid strands wound multifilar) ,b/ copper foil (with insulation tape pre applied by a tae fab house) orc/ solid CuThe Pcu losses were largley resistive and rather than dominated by skin or prox effects.Bigger issue was Pfe so core material choice for Pfe vs F and Thotspot was much more important.Thus we avoided TIW/Litz even though it was available since decades.Hope this old Dinosaur of an EE (1968!) can still pass on some bits of knowledge in my closing chapters...YOU HAVE AN ABSOLUTELY FANTASTIC DAY!JonPSOT OT OT !!! attached recent historic reconstruction 1942....

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 08, 2023, 01:34:00 pm
content: I've also seen TIW on CMCs, to remove the separator/spacer and pack just a little more into it. You could even do twisted pair/bifilar, though you'll probably need a DMC separately if that's the case; so there's still some value in having the windings separated (split bobbin / sectoral wound toroid), not overlapping.Conversely, if you need a DMCanyway(as with some CCM PFCs, say?), might as well save some space on the CMC, eh? If space is at a premium, that is.Working on a high efficiency design right now, which looks like it's going to need litz in multiple locations. (Not necessarily TIW AND litz, at least.) There's absolutely no other way to get Q high enough for BCM/QR and LLC type converters. Solid foil/sheet is possible to use, but sparingly, like, low voltage secondaries only.Tried planar design in the LLC transformer, it sucked -- you can't exactly get multiple layers of foil out of such a transformer, and wire them together all in parallel. There's no current path that way, either it goes sideways through interleaved contacts (stacked stitching vias?) with considerable crowding, or it does edgewise around the foil (even worse). The best seems to be duplicating the output rectifier per layer [foil sheet]: tedious and probably expensive, not to mention a thermal mess.Did a comparison of TIW/conventional on its aux/standby supply; being able to push fill factor is well worth the slightly increased diameter of TIW, especially if shields are required. This example isn't hugely significant, as it's not a highly optimized transformer -- it has to be big because it has multiple windings (and maybe shields, we'll see, hasn't been to EMC yet) and a high aspect ratio, not because of power.That said, I have seen plenty of modern compact (low power) designs that look to be using TIW to optimize their transformer. Like, what else would you even do, in a transformer that's so small that, using margin tape, you'd be left with literally zero winding area at all? Phone chargers (as we know them) practically couldn't exist!Tim

author: uer166
author_rank: Super Contributor
timestamp: May 08, 2023, 07:14:33 pm
content: Quote from: jonpaul on May 08, 2023, 08:36:31 amWhat was the efficiency?When you need 98%+ efficiency at 40kW, I'd love to see a design of a reasonable size thatdoesn'tuse Litz. Horses for courses, both Litz and TIW (and both together) have a place.

author: jonpaul
author_rank: Super Contributor
timestamp: May 09, 2023, 05:57:54 am
content: Uer166:Our work and experience was not at 40 kW, nor did we make precice efficiency tests.A SMPS efficieny will depend on many losses in addition to the transformer Pcu, Pfe. The Pcu will be reduced by litz but use of TIW may reduce the fill factor of the bobbin.A 40 kW HF supply will very likey use multiple transformers and foil at least on the secondaries.Jon

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 09, 2023, 03:24:15 pm
content: Heh, last 40kW design I was involved in, we used lots of litz... since the alternative was water cooled tubing. Managed to avoid that on the transformers (air/conduction cooled wire; a water-cooled heatsink band around the toroid cores). Efficiency was more or less N/A, as we didn't have a way to measure the (HF) output directly, and the load is much worse anyway (induction heating). Would've been in the 90s % range; think the thermal calculation was something like 300W at full load, per 5kW inverter module (with one transformer per module, secondaries wired in series, hence the modularity).Tim