Transformer markings ... - Page 1
Forum section: electronics / beginners

author: Phyvel
author_rank: Newbie
timestamp: August 31, 2014, 11:17:12 am
content: Ok ... So I'm a tad new to this electrical engineering thing. Alright, alright; I'm still in university. Anyway, I'm tearing down some electronics (flouro-lamps, power supplies, et cætera), and I'm coming across a lot of transformers, with little or no markings on them. Obviously, finding the ratings of the ones which aren't marked can be impossible, without testing them. However, the one's which are marked, I'm not sure how to read. IE, 4.0(118)1.4. Can anybody help me with this? Puh-leeeeeeeeeeeease?

author: German_EE
author_rank: Super Contributor
timestamp: August 31, 2014, 12:03:31 pm
content: Without a manufacturers datasheet you can only make an inspired guess, especially when it comes to switched mode transformers. As a rough guide the bigger the core and/or the thicker the winding on the secondary the higher the deliverable current.For a 50/60 Hz transformer there are formulas that help you get an approximate figure:S = 1,1 x ((VA)^2)S = core section in cm2VA = power in Volt x Ampereor VA = (S / 1,1 ) ^2example S = 2 cm X 3 cm = 6 sq cm(6/1,1)^2 = 30VA

author: Phyvel
author_rank: Newbie
timestamp: August 31, 2014, 04:50:35 pm
content: QuoteI was really hoping I would only need to dissect the ones with no markings. I was hoping, even farther, that those markings actually meant something, on the ones which had them.I've attached a picture of a few, with which I am currently dealing. The ballast is from a fluorescent eco-bulb. the others (if I remember correctly) came from a laptop power supply, and a power inverter for el-wire/tape (9 to 12 —Vin -> 110 ~Vout).Lucky for me, "Electrical Machines" was one of my strong topics ... Unfortunately, though, we didn't cover transformers in great detail.

author: IanB
author_rank: Super Contributor
timestamp: August 31, 2014, 05:48:02 pm
content: Transformers like that most likely have been custom designed for that particular application. They probably are not generic items out of a catalog.The best way to characterize unknown parts is to measure them. If you unsolder transformers from the circuit then with the right instrumentation and knowledge you should be able to determine various properties like turns ratio, inductance, core saturation and so on.

author: Phyvel
author_rank: Newbie
timestamp: August 31, 2014, 06:15:37 pm
content: Maybe I should have asked the question a little differently. I am in university, for electrical engineering, I understand how to test/characterize most things electrical/electronic, but I do not currently have the tools (at home) to characterize unknown trafos, without counting turns by eye, and measuring wire diameters, air-gaps, et cætera, with my calipers. My question is; Is there a way to tell, from the markings, with what values I am dealing? I have about 100 such trafos, and would like to save time. The don't teach how to read factory markings on machines, in my university (save for motors and generators). Kay? Good.

author: IanB
author_rank: Super Contributor
timestamp: August 31, 2014, 06:31:54 pm
content: Quote from: Phyvel on August 31, 2014, 06:15:37 pmShort answer: no.The parts are bought to spec, to do a precise job. They are not generic.Even if you could find out who the manufacturer was, the specification would be confidential and proprietary between the purchaser and the supplier.

author: Phyvel
author_rank: Newbie
timestamp: August 31, 2014, 06:37:00 pm
content: QuoteI was somewhat afraid of that answer. I guess I need more/better equipment at home. Otherwise, the university is going to be reeeeeeeeeal tired of seeing me in the lab, doing private tests. They're kinda nazis about that stuff here, at Politechnika.Thanks for the advice, at any rate.

author: bktemp
author_rank: Super Contributor
timestamp: September 01, 2014, 12:26:07 pm
content: From the parts in your picture only the yellow one on the right side is a transformer. The toriod core one is a common mode filter (2 inductors on the same core), the yellow part in the ballast is an inductor.To measure the transformers/inductors you need a LCR meter or a signalgenerator and a scope. Otherwise you can only guess from the size and the number of turns visible.

author: Phyvel
author_rank: Newbie
timestamp: September 01, 2014, 02:22:03 pm
content: Quote from: bktemp on September 01, 2014, 12:26:07 pmOkay, I'm assuming you can tell the one on the ballast is an inductor, due to it's use. How are you able to tell the difference, otherwise? I mean, with further inspection, you are correct. On the one from the ballast, from looking at the through-holes, there are only two leads on it. While the one on the right, has what one might expect from a trafo. The black, toroidal one, was my stupid mistake. I must have been drunk, when picking out which ones to picture.

author: bktemp
author_rank: Super Contributor
timestamp: September 01, 2014, 03:31:17 pm
content: Quote from: Phyvel on September 01, 2014, 02:22:03 pmHaving only the transformer without a circuit around it, it is almost impossible to tell what it is good for by only looking at it. You have to measure its values.With the circuit around it, it is much easier. One example: If it is a power supply, it will have capacitors. From their voltage rating you can estimate the ration of the windings. From the current rating of the rectifier diodes you can estimate the current. Looking at the circuit around the transformer and you can tell if it is a transformer for full or half brigde converter (2 or 4 transistors at the primary side, additional inductor after the rectifier at the secondary side) or a flyback converter (single transistor at the primary, only diodes at the secondary side). Depending on the switching power supply topology the transformer will have different properties.

author: Phyvel
author_rank: Newbie
timestamp: September 01, 2014, 03:46:55 pm
content: Quote from: bktemp on September 01, 2014, 03:31:17 pmSo what you're saying is, I really need to learn hownotto tear things apart right away. Thank you for the helpful advice.I should have learned that from watching Dave's videos, but somehow ... Didn't.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 01, 2014, 04:31:46 pm
content: IME, it is rare for a commercial product to use a "stock" transformer. Because of economics, virtually ALL of them are (AmEnglish) custom or (BrEnglish) bespoke and will carry OEM numbers that mean NOTHING at all to anyone except the maker and the buyer. ESPECIALLY with inductors,context is everything.Once removed from their original circuits they become nearly impossible to decipher. Even if you measure them and discover the basic specs, it is almost impossible to work back to what circuit they were designed for.

author: Phyvel
author_rank: Newbie
timestamp: September 01, 2014, 04:42:31 pm
content: Quote from: Richard Crowley on September 01, 2014, 04:31:46 pmI might be pissing up the rope, to find out for what circuit they were intended; Am I doing the same, to figure out howIcould use them?

author: bktemp
author_rank: Super Contributor
timestamp: September 01, 2014, 05:37:52 pm
content: The easiest way to use a transformer: Use the same parts that were used in the original circuit.From my experience: Most of the salvaged transformers are not useful because the output voltages are application specific. Only single output transformers or other more common types like from pc power supplies are quite usable.If you want to use an inductor or transformer in your own circuit you need to know 3 values: Inductance, max. rms current and saturation current.Inductance can be measures using an LCR meter or a scope and some driving circuit.Rms current rating can be guessed from dc resistance and size. The saturation current can be measured with a circuit like this:http://elm-chan.org/works/lchk/report.htmlThis also allows inductance measurments.When you know the inductance and saturation current, you can calculate the amount of energy the inductor can store. This is necessary for transformers used in flyback converters to design the circuit around it.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 01, 2014, 06:05:27 pm
content: Virtually ALL of those small OEM transformers are made for a SPECIFIC circuit, and you would need considerable circuit development skills to re-use it in a different circuit. If you have to ask, assume you can NOT re-use them for a different circuit. I certainly don't have the skills (or the time, given the very low value of the components) to re-use transformers like that. And for that reason, I consider those small transformers to be non-reusable and not worth salvaging. I suspect many (most?) others here have the same attitude about them. Simple (2-terminal) inductors are one thing, but those small OEM transformers are pretty much the LEAST recyclable/reusable of all electronic components. That includes RF transformers, IME.