Talk:Transformer/Archive 3

message: I have no doubt that high voltage transmission development continues, and I suspect that transformer development continues in that area, but I don't think the sentence that has been questioned fits very well or contributes much to the introduction. I think that I will offer an alternative. --C J Cowie 19:20, 16 January 2006 (UTC)
replies: text: The article use to say that transformers were essential in the continuing development of the high voltage network. I dont think there is much development going on now in high voltage networks, and that that is, is not depending on transformers, but on advanced forms of switchgear automation, telecontrol, condition monitoring of plant etc.--Light current 23:19, 16 January 2006 (UTC)
replies: text: Please sign comments. You are misinformed, high-voltage networks are ongoing topics of research, construction continues to expand high-voltage transmission, and transformers are critical elements in that expansion.  Please keep up with the literature, (for example, publications of the IEEE Power Engineering Society, abstracts are available online) before making such a huge generalization.  --Wtshymanski 23:09, 16 January 2006 (UTC)

text: I am not sure that you are asking about what I wrote in the intro or what Wtshymanski wrote above. What I wrote refers to "tricks" with transformers to reduce harmonics introduced in power systems by nonlinear electronic circuits and in motors by electronic motor controls. I suspect there are other examples. --C J Cowie 23:49, 16 January 2006 (UTC)

text:  The article used to say "the transformer has played a substantial role in the development of electrical networks". --BillC 22:23, 16 January 2006 (UTC)

text:  Indiana REMC Powering Customers With Soy and Envirotemp® FR3™ Fire-Resistant Fluid are a couple of examples of recent improvements to transformer oil. Maybe it would be hard to get more efficient, but environmental issues, safety and reduced costs are always being researched. (not that it needs to be in the introduction) --Dual Freq 22:32, 16 January 2006 (UTC)

text: I was actually thinking of this revision when I said it was not  accurate.--Light current 22:59, 16 January 2006 (UTC)

text: This is agreed as a good point. I was not aware it had been removed. Can we put it back to wherever it came from.?--Light current 00:54, 17 January 2006 (UTC)
replies: text:  I removed it because a) it's not generally true - usually it's cheaper to bring coal to a power plant than to transmit power from a remote plant and b) the article is about transformers, not about electric power transmission, which has its own article and is a mouse-click away. Gotta make room for all the gearboxes. I'm also unhappy with the format of the "electrical laws" section - which I think is wordy, though at least accurate.  --Wtshymanski 02:35, 17 January 2006 (UTC)

text: I agree with Wtshymanski. Power stations are located as close as practicable to points of demand considering such factors as the price and availability of large plots of real estate in urban areas, environmental concerns, and locations of rail lines etc. for coal access. High voltage transmission is essential, but the economic picture shouldn't be explained here. --C J Cowie 02:55, 17 January 2006 (UTC)

text: Not over here (UK) they're not. Theye located very near coal fields and sources of water. Nuclear ones almost always on the coast.--Light current 03:08, 17 January 2006 (UTC)
thread_title: Introduction

message: I have proposed a merger of Tap (transformer) and Tap changer. Comments should be posted here: Talk:Tap (transformer). BillC 21:02, 17 January 2006 (UTC)
thread_title:  Transformer tap articles 

message: http://en.wikipedia.org/w/index.php?title=Transformer&curid=30906&diff=36038301&oldid=36037749
i'm sure at least in PA type setups the tap changers on the transformers (which are usually driven from a 100V line source) are used to set the power of the individual speakers.... Plugwash 02:39, 21 January 2006 (UTC)
replies: text: Well it may alter the power slightly but thats only because of impedance matching/ mismatching. On 100V line I think the o/p Z is normally higher than your home hi-fi for max efficiency and to avoid losses on the long leads that are used.--Light current 02:42, 21 January 2006 (UTC)
replies: text:  You are misinformed. I've usually seen it as 70 volt distribution systems.  Consider two speakers on a PA system. You need a 50-watt speaker for the auditorium, and a 1 watt speaker for the janitor's office. Instead of calculating impedances all over the place and having a different impedance for every single speaker rating (and system power rating), you step up the output of the main PA to 70 volts (or 100 volts), and run that all over the building.  Each speaker, be it 4, 8 or 16 ohms impedance, gets its own transformer which will have taps on it, marked "10 watts", or "1 watt" or what have you. It alters the power delivered to the speaker a great deal, which is kind of the point. Do the math and you'll appreciate the ingenuity of the system. 
--Wtshymanski 02:53, 21 January 2006 (UTC)

text: Well, if you've seen the actual markings on the transformers, I guess that settles it. But over here systems are normally 100V line and used outside in the open air with highish Z horn speakers for PA. Im not sure if transformers are actually used at the speaker end or just at the amp o/p.--Light current 03:00, 21 January 2006 (UTC)
replies: text:  See , for example, and about 2 million other Google hits on "70 Volt PA system".--Wtshymanski 03:08, 21 January 2006 (UTC)

text: Ah I see the speakers at that link have their own built in transformer (which puts the price up I suppose). Those speakers are different fron the ones I was thinking of.--Light current 03:12, 21 January 2006 (UTC)
replies: text: Another thing to remember, not all amplifier output stages are designed for impedance matching as such. if your using a single transistor pulling against a resistor then sure matching may make sense, if you are using a push pull output stage with negative feedback taken from its output then the output impedance of your system can be very low indeed. but if you matched the load to that impedance you'd fry the transistors! Plugwash 03:28, 21 January 2006 (UTC)

text: It does appear that the same system is used over here also (but 100v line is more common here) for PA in hotels, large buildings etc. The system works by making the speaker look like lower or higher impedance depending on the power you want (or can handle) at each speaker. Saves using Hi Z exp horns!--Light current 03:32, 21 January 2006 (UTC)

text: Well i was originally assuming that the discussion was about domestic radio speakers fed from a valve amplifier in which case any tappings on the output transformer would be to match the Hi o/p Z of the valve stage to the much lower Z of the speaker.--Light current 03:38, 21 January 2006 (UTC)
thread_title:  speaker transformers 

message: In an ideal transformer,  mag flux is not needed and is in fact equal to zero. Discuss in less than 100 words (10 marks)--Light current 01:15, 24 January 2006 (UTC)
replies: text: I think you have confused flux with ampere-turns. The flux is the energy-coupling mechanism between primary and secondary. Without it, there is no transformer. An ideal transformer requires neglible ampere-turns to set up the flux, but it does not produce zero flux. Secondly, I have to agree with Wtshymanski, an image caption is not the place for point-making. That diagram is to show an ideal transformer, around which the arguments in the surrounding text develop. BillC 01:23, 24 January 2006 (UTC)

text: Not necessarily. The ideal core material does not exhibit saturation. An ideal transformer has no leakage, no winding resistance and no magnetic losses. Loss-free does not demand zero reluctance in the magnetic path. BillC 01:43, 24 January 2006 (UTC)
thread_title:  Whats the good of flux? 

message: Caption gives wrong impression that an ideal transformer needs flux. It doesnt!--Light current 01:19, 24 January 2006 (UTC)
replies: text: Can you provide a reference that supports the statement that there is no flux inside an ideal transformer? You are confusing magnetomotive force in the magnetic circuit, which is affected by the presence of a current in the secondary, with flux, which is not. See, for example  BillC 02:04, 24 January 2006 (UTC)
replies: text: Wtshymanski beat me to it. The argument presented there is invalid because it is dealing with a mathematical singularity: there is an inherent division by zero (the reluctance of the magnetic path) in that equation. The fact is that an ideal transformer with zero losses, perfect coupling and no reluctance is not merely physically unrealisable with practical materials, it is in fact mathematically impossible, implying as it does that there is an energy transfer from primary to secondary with no energy storage in the intervening medium and that there is a flux density B which exists without a flux Φ. The reluctance of an ideal transformer may tend towards zero, but it may not actually be zero. As a side issue, consider what the voltage induced on an open-circuit tertiary winding would be if the secondary is put on load. Zero, or non-zero? BillC 17:10, 24 January 2006 (UTC)

text: But your book doesn't say the flux is zero, does it?  If there was no flux, there'd be nothing linking the primary and secondary windings and no way to transfer energy. What your book *probably* says is that if the permeability of the core material is infinite, it requires negligable *current* to establish the flux. You must have flux - by definition of a transformer. Do a Google search on "ideal transformer infinite permeability" and you'll soon hit about a thousand sets of lecture notes that discuss this. Primary and secondary MMF (magnemotive force, ampere-turns) must sum to near zero in the ideal case - an ampere-turn in the secondary must be offset by an ampere-turn in the primary. Your reference may not be wrong, but you may be reading it in an entirely idiosyncratic way not accepted by the rest of the world. --Wtshymanski 22:54, 25 January 2006 (UTC)

text: Here's an analogy for you.  A transformer without flux is like a gearbox without teeth (though I can think of at least one example of a toothless "gear" box so the analogy isn't perfect). --Wtshymanski 18:57, 26 January 2006 (UTC)
replies: text: I think you're probably right, LC, but please leave the caption alone.  Every physically realizable transformer has flux in the core.  That's how they work.  For people trying to find basic information on transformers, it would be misleading to imply that there is no flux.  The image in question is idealized, even if it's not actually an ideal transformer, because only the flux in the core is shown.  Ideal transformers can pass DC, too, and do lots of other weird things that the article says they can't, but talking about this here would jsut be confusing.  Pfalstad 01:50, 27 January 2006 (UTC)
replies: text: Ok, well the new caption as it stands seems fine to me, except that you misspelled magnetizing. :)  Pfalstad 02:11, 27 January 2006 (UTC)
thread_title:  Transformer diagram caption 

message: No, the paradox is due to our simplified model.  In a real transformer, among other issues, the secondary does not instantaneously resist changes to the flux.  There is speed of light delay.  With a time-varying primary current, there must be some flux even if there is no leakage.  Pfalstad 04:13, 28 January 2006 (UTC)
replies: text: How much delay do you get when pushing a wall?--Light current 04:17, 28 January 2006 (UTC)

text: Im saying your delay thing is a bout as relevant to the delay in pushing a wall. Its irrelevant--Light current 04:24, 28 January 2006 (UTC)

text: Well they probably are TLs, but Im not going to get into that one just yet! (Just remebered - transmission line transformers are in fact TLs! How strange!)--Light current 23:01, 28 January 2006 (UTC)
thread_title:  Relativistic transformers? 

message: Just found this analogy in your link!
The step-up/step-down effect of coil turn ratios in a transformer is analogous to gear tooth ratios in mechanical gear systems, transforming values of speed and torque in much the same way:
So Im not the only one who thinks that gears are a good description of transformer action!--Light current 02:58, 24 January 2006 (UTC)
thread_title:  Analogies: 

message: Although transformer windings usually heve considerable inductance (of the order of henries), only that portion due to leakage flux that does not couple both primary and secondary windings, contributes to the series impedance of the transformer.
however the rest would surely appear as paralell impedance which would still draw VArs out of the supply. Plugwash 02:47, 25 January 2006 (UTC)
thread_title:  inductance 

message: I think it is necessary that a transformer have high inductance in order to work; the higher the inductance of the primary of a (lossless) transformer, the more ideal it is.  An ideal transformer has infinite input impedance, and a large inductance approximates that.  Pfalstad 03:07, 27 January 2006 (UTC)
replies: text: Some high frequency  (RF) transformers (like transmission line transformers) have very low winding inductances. It all depends how low in frequency you want to go!--Light current 03:13, 27 January 2006 (UTC)

text: Agreed--Light current 03:38, 27 January 2006 (UTC)
thread_title:  Importance of High Inductance