Ethernet transformwer with 4kV isolation

is there such a beast?

My ethernet circuit floats at ~ 240AC mains and I'd like to use the Ethernet transformer for Isolation.

Most I have seen is 1kV

Or should I look else where to put my Isolation barrier.

Regs Joe

Reply to
Joe G (Home)
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This just screams "fiber."

Reply to
robertwessel2

This just screams "fiber."

==> Joe ==> Can you suggest low cost fiber solution?

What key word should I be search in Google for?

Regards joe

Reply to
Joe G (Home)

"ethernet optical transciever"

If you can live with fast Ethernet, something like an Avago AFBR-5803AQZ is about $30 in small quantities. Or Gb Ethernet with something like an AFBR-53D5Z is about $50. I think you can probably find fast Ethernet parts down to about $20 (but don't put too much stock in that - in either direction).

If you have just one or two problematic installations, an external copper-to-fiber converter ($100-$200 each for GigE) or two is a simple way to deal with the problem.

Reply to
robertwessel2

Are you saying that you have one ethernet phy at earth potential, a second at ~240VAC and the cable floats? Can you use a gas tube surge suppressor on the cable pairs to earth ground?

Reply to
Jim Stewart

Surely you've heard of Ethernet over Power?

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mac the naïf
Reply to
mac

No, but I've heard of Power over Ethernet. That's only 48VDC though...

Reply to
Grant Edwards

Forgot the ;)

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mac the naïf
Reply to
mac

You can get medical grade isolation transformers for Ethernet. Not sure how much this one costs but they are usually well north of $100:

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You'd have to ask them where they can be bought in Australia. Or maybe you guys have local suppliers for such transformers. The IT department of a large hospital might know.

But I am not sure your 240VAC floating setup is legit in the first place.

--
Regards, Joerg

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Reply to
Joerg

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IMHO, I don't think it would pass UL, CE or CSA without approved high side components and creepage distances.

Then there's the issue of the cable and connector insulation and touch distances...

Reply to
Jim Stewart

What so special about that ?

AC/DC radios for 220/240 V mains had series capacitors on the antenna and antenna ground terminals rated at 3750 Vdc.

Tube televisions for 220/240 V mains used a half wave rectifier and hence the internal chassis was either at the neutral potential or riding at full phase voltage (220/240 V). For this reason, the number of external interfaces was very limited. On the antenna side it was quite easy to have sufficient isolation with heavily insulated wires on different holes on the ferrite core. The external loudspeaker was also quite easy to arrange, since an audio output transformer was needed anyway.

Feeding early computer games or teletext into the video chain of such AC/DC receiver required some optoisolators (4N25 etc.).

Various standards require 1500 V or 2500 V (typically DC for at least a minute). The reason for such high voltages (compared to the RMS voltage) is that such peak voltages really exists in a typical mains powered circuit.

A steep pulse current in the live conductor will generate also a significant voltage drop in the neutral connector due to the neutral wire inductane/impedance and hence the voltage can be significantly higher than any grounded potential.

For the OP, the simplest thing would be to use some standard Ethernet/fibre converters and use 0.1 - 1 m of fiber between the grounded electronics and the other system riding on 240 V mains.

Reply to
upsidedown

Yep, It's all about how you interpret the safety standard.

I was attacking it from the point of view that there is already a transformer so lets just a high isolated one.

There other places in the circuit where the safety barrier can be out.

By the way are you in OZ

Joe from Melb.

Reply to
Joe G (Home)

If you are making a low volume product and intend to sell it all over the world, in practice, the simplest thing is to do some "overenginering" and in this case use some fiber, even if you could get rid of simple optoisolators in a particular market.

Nope, sorry too disappoint you, but your guess is off by nearly 20000 km :-).

Reply to
upsidedown

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Obviously, it has passed:

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Quote: "The MI 1005 is approved to following standards: DIN EN / IEC

60601-1:2007 (3rd Ed), DIN EN / IEC 60601-1-2:2007, UL 60601-1"

If in doubt about the cert of a part ask the vendor for a copy. I always got that upon request.

Well, yeah, of course your installation is not supposed to compromise the isolation provided by the device. The same goes for just about any part with a test certificate.

--
Regards, Joerg

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Reply to
Joerg

The part needs to be rated for that purpose. It probably is, but if it goes into a product I would not release it without written confirmation by the vendor that it's ok. This goes for all parts, including the supply to that device.

I've repaired a lot of those. Not all had that rating on the caps. But I bet the mfgs all had copies of the certs for all parts that crossed that barrier, locked away in steel cabinets :-)

There you said it, for one minute. Huge difference, as HV barriers can "age" with application of HV over time. Some do, some don't. Therefore, I can only repeat my advice: Get it in writing.

Fiber is one of the safest method. But can get expensive.

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Regards, Joerg

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Reply to
Joerg

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Sorry I wasn't clear. I'm not questioning the approval of the medical grade transformers, just the 240VAC floating setup. Even with the medical grade transformers, I question whether you could get the design approved by any safety standard.

Reply to
Jim Stewart

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Yes, that's why I pointed out that the OP should investigate whether the

240V floating setup is legit in the first place.

In the end you usually need a "whole system" approval anyhow.

[...]
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Regards, Joerg

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Reply to
Joerg

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