Talk:Isolation transformer/Archive 1

Archive 1

Protecting Audio-Video equipment

How do we fully protect the home AV equipment in case of any possible problems in the mains power network (fluctuations, noise, etc)? I read that there are seven types of power problems. So how do we protect our consumer electronics against all these problems, without loosing quality in sound and video? I was informed about two solutions: 1/. On-line UPS or 2/. Isolation transformer and Power Conditioner. But these two solutions, as i was told, affect the quality of the sound. Does anyone know why this happens? What are the advantages and disadvantages of these two solutions? Why is the isolation transformer used in our case, how does it protect? Are there other solutions? Leo67 (talk) 11:00, 28 March 2008 (UTC)

Where does the potential difference come from?

Grounded objects near the device under test (desk, lamp, concrete floor, oscilloscope ground lead, etc.) may be at a hazardous potential difference with respect to that device. By using an isolation transformer, the bonding is eliminated, and the shock hazard is entirely contained within the device.

Why should there be a potential difference between the DUT and objects near the DUT? And if there is a potential difference, shouldn't the earthing system and its circuit breakers prevent bad from happening? Thanks, --Abdull (talk) 20:05, 31 January 2010 (UTC)

As an example, most switching power supplies (such as used in TVs, PCs, etc.) connect a bridge rectifier directly to the AC input. There's about 165VDC (in the US) across the reservoir caps but the negative side of those caps (so-called HOT ground) are about -83V w.r.t. Earth. So, for example, if you forget to use an isolation transformer and you try to connect an oscilloscope ground lead to the HOT ground, you will most likely vaporize some PCB tracks and blow a fuse or three. Alfred Centauri (talk) 23:09, 31 January 2010 (UTC)

Earthing one end and safety

I've inadvertently restored a sentence that had been deleted with comment. I'll let the restoration stand, and justify it here.

The sentence is:

• Earthing one end of the secondary makes an isolation transformer less safe for working on live equipment, as discussed above; but if neutral is connected to earth a fuse will blow or circuit breaker trip (if fitted!) if the transformer fails in certain ways or the live output gets shorted to earth—a desirable and safe outcome.

• The comment: I still think this is redundant...longer, but not clearer.

It's not redundant in the sense of repeating something already said; I don't think this point is addressed at all in the article (I'll recheck, have been known to miss things). I don't think it's redundant in the sense of not needed; noise is often given as the reason for earthing the secondary, but this is relevant and perhaps more important. I haven't given a reference, but would comment that it's fairly obvious that this happens, and that it's a good thing.

Pol098 (talk)

I'm not sure how I'd describe someone who purchases a very expensive isolation transformer and then grounds the secondary. "Dumbass" is the first word that comes to mind, but I've been called cynical. Should we also advise that baring the wires of the transformer leads and wrapping the energized bare ends around the tounge will lead to acute discomfort and perhaps death? Really, do we need to describe all the ways an idiot can go wrong here, or should we confine ourselves to the intended use of an isolation transformer? Since the (primary) neutral is already connnected to earth, the above sentence is wrong anyway. --Wtshymanski (talk) 16:00, 7 July 2010 (UTC)

120:120 instrument transformers are called isolation transformers and their secondaries are almost always connected to the same ground the primary is connected to. This is done for phasor reversal of 180 degrees. Just because an isolating transformer is not designed for human safety and incorporating a big isolation factor design, such a medical operating room usage types, doesn't mean it isn't called an "isolation transformer". The term is used due to not having a step-up or step-down voltage transformation and lack of a better name. These are also called "reversing coil" and "reversing transformer" in the industry. 174.118.142.187 (talk) 13:39, 3 May 2013 (UTC)

With respect to Pol098's comment. I don't like taking out breakers by passing that amount of current through my body when working on equipment. You missed the point of a safety isolating transformer 174.118.142.187 (talk) 13:43, 3 May 2013 (UTC)

Avoiding Ground Loops

I use an isolation transformer in the following setup: - PC (connected to mains) - Device under test (few watts, mains supply plugged in isolation transformer) - USB-based measuring tool (logic analyzer) from PC to DUT

(See https://en.wikipedia.org/wiki/Ground_loop_(electricity)#Solutions) — Preceding unsigned comment added by 188.86.109.11 (talk) 13:59, 3 October 2017 (UTC)

how to link the page to Chinese version of 隔離變壓器(isolation transformer)?

there is the corresponding part of 隔離變壓器(isolation transformer) in the page of 變壓器(transformer) in Chinese, but I don't know technically how to connect this article with the Chinese version. Should I open a new article of 隔離變壓器(isolation transformer), and then link it to this article? — Preceding unsigned comment added by 高達賓 (talk • contribs) 23:27, 13 November 2017 (UTC)

Why would you want to do that? Look at [ https://meta.wikimedia.org/wiki/List_of_Wikipedias ]. it would be a huge job if every article linked to every similar article in another language. --Guy Macon (talk) 20:04, 23 March 2021 (UTC)

Dangers of misunderstanding what constitutes an isolation transformer.

In rejecting changes I made to this subject a few months ago, Mr. Macon said

"Nonsense. There is no safety issue associated with neutral to ground bonding at the secondary.

Please discuss your concerns on the article talk page. See [ https://www.tripplite.com/isolator-series-120v-250w-isolation-transformer-based-power-conditioner-2-outlets~IS250#section-features "

The referenced document from Tripp-Lite does not represent the product as an isolation transformer, rather as an "isolation transformer-based power conditioner".

An appropriate interpretation of that sentence is that the product type is "power conditioner", and "isolation-transformer-based" is a limited description of some aspect of the product.

Their statement that this offers "complete line isolation" is clearly wrong.

Medical Grade isolation transformers and many other types are required NOT to bond either output terminal to ground, to reduce risk of electrocution.

See W0QE: #68: Isolation Transformer Warning! https://www.youtube.com/watch?v=Ek_GrhY7r5A&t=50s

There are many similar warnings from those engaged in electrical product repair citing the dangers of using an isolation transformer that is not correctly isolated. Here is another: "How not to blow up your oscilloscope". https://www.youtube.com/watch?v=xaELqAo4kkQ

Or: Dangers of working on All-American 5 radio; proper use of isolation transformer. https://www.youtube.com/watch?v=mYY-jvyuA5s&t=447s

The topic is sufficiently complicated that misunderstanding the different kind, types and extent of "isolation" would be greatly reduced. It appears to this writer than the waters are muddied mainly by financial incentives of sellers to supply inadequate product.

For these and other reasons, I reject the reversion and change it back. [1]

Fabrice002 (talk) 19:02, 23 April 2021 (UTC)

Here are the edits in question:[2][3]

Fabrice002, Do you have anything other than your original research based on your interpretation of some Youtube videos, none of which directly support your "does not provide the type of isolation needed for safe electronics work" claim?

Dave at EEVblog is a recognized expert and thus is considered a reliable source, and could be used for a claim about where and where not to use the various types of isolation transformers, but certainly not for your overblown "does not provide the type of isolation needed for safe electronics work" claim. --Guy Macon (talk) 22:06, 23 April 2021 (UTC)

Another unsourced claim is "Medical Grade isolation transformers and many other types are required NOT to bond either output terminal to ground". If you have a reliable source for this please post it. In particular the Youtube video you posted , [4] claims that an ECA ECA500-1 extreme isolation transformer as supplied from the factory is dangerous depute being approved by UL, CE, and CSA, and despite being in use in thousands of hospitals (it is even covered by ANSI/AAMI standard ST63-2002: sterilization of health care products). --Guy Macon (talk) 01:26, 24 April 2021 (UTC)

Consider two isolation transformers on hospital carts with patient monitors on them.

One, which I will call "not-to-code", is wired as Fabrice002 suggests.

The other, which I will call "UL/CE/CSA/NEC", has output the neutral connected to ground as seen in the Tripplite, ECA, etc. transformers.

Assume that the isolation transformers can output 15A@120V (the rating of the most common US 120V outlet). Note: In the US it is illegal to fuse the neutral or ground wire so the transformer has a 15A fuse on Hot only.

Plugged into not-to-code and UL/CE/CSA/NEC are patient monitors that are fused at 1A.

Both patient monitors have a fault that connects Hot (after the 1A fuse) to case (which connects to Ground).

The PM plugged into UL/CE/CSA/NEC blows a fuse.

The PM plugged into not-to-code continues operating. Hot and Ground are at 0V relative to the case. Neutral is at 120V relative to the case.

Ah, but these carts have GFCI outlets. The GFCI will interrupt the circuit if there is an extra 6 mA coming in through Hot that doesn't come back through Neutral. (Which means that it is probably going through a human body to ground). This can happen when the human contacts a live wire because of a damaged power cord. And it is super easy to touch the threaded part of a light bulb while changing it, which is why lamps now have polarized cords.

On the UL/CE/CSA/NEC cart the power comes from the 120V Hot, through the human, to the case, and back through the ground wire. (Hot is not connected to case because of the wiring fault -- the blown fuse opened that connection, and Ground is only connected to Neutral upstream of the GFCI). The GFCI senses an imbalance between Hot and Neutral, trips, and a life is saved.

On the not-to-code cart the power comes from the 120V neutral, through the human, to the case, and back through the Hot wire (which is now connected to the case because of the wiring fault). The GFCI senses the same current on Hot and Neutral, doesn't trip, and somebody dies.

An accident investigation shows that Fabrice002 wired it that way -- violating the electrical code -- because some dude on YouTube said it was better that way. :( --Guy Macon (talk) 12:11, 24 April 2021 (UTC)

Untitled

Dear sir please send me details of working of transformer isolated barrier.can i get the ckt diagram that how it will work ?please send urgently. regards Umesh

Ground Fault Isolation We are using 120V commercial grade electronic ballasts, properly grounded, rated at 2Amps to drive two low pressure UV lamps submerged in water rated at 800mA. System requirements are to use GFI barkers with each ballast. This installation in a wastewater treatment plant, where there are motors, pumps and air compressors. GFI’s are randomly tripping at 5mA from ballast electronic current leakage up to 9.2mA. Can we resolve our nuisance GFI tripping by using 120V to 120V isolation transformers between the GFI and electronic ballast?

You've probably got a defective ballast or defective GFCI breaker.

Ivannewman 00:41, 19 June 2007 (UTC)

Wikipedia is not the place for such queries. I don't think that the bit of how-to information about connecting two power transformers symmetrically to create an isolation transformer belongs here either. Eikimart 19:58, 16 August 2007 (UTC)

Wiki Education Foundation-supported course assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 25 January 2021 and 16 May 2021. Further details are available on the course page. Student editor(s): Josepazmino. Peer reviewers: Regulinecoast1.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 09:40, 18 January 2022 (UTC)