Where to find 230V - 24V transformer - Page 1
Forum section: electronics / beginners

author: chiken
author_rank: Contributor
timestamp: March 25, 2019, 09:41:40 pm
content: What do you guys where i could find 24V (min. 3A) transformer,i've been salvaging quite a bit and repairing some stuff,but i did not really encounter a 24V transformer, or am i missing something?(EUROPE)

author: james_s
author_rank: Super Contributor
timestamp: March 25, 2019, 09:48:04 pm
content: 24V is often used in industrial controls. Sometimes you might find a 12V transformer with dual secondaries you can wire in series. If you're willing to buy new then 24V is readily available, guy could also look on eBay for local items.

author: xavier60
author_rank: Super Contributor
timestamp: March 25, 2019, 10:02:28 pm
content: For my current bench supply project, I bought this transformer from a local Jaycar store. The same thing might be available in your country also.https://www.ebay.com.au/itm/12V-30V-100VA-6A-Multi-Tapped-Dual-Type-2170-Transformer/254143529997?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20140106155344%26meid%3Dc3c31df6399e4f6e8fdfd27c9fc3d5da%26pid%3D100005%26rk%3D2%26rkt%3D7%26sd%3D391912226691%26itm%3D254143529997&_trksid=p2047675.c100005.m1851Although it can be configured for 24VAC, I'm relay switching the secondaries for parallel 15VAC or series 30VAC.Keep in mind that a derating factor needs to be applied when the secondary output is rectified and filtered. I'm expecting that my project will safely supply 4 amps on its low voltage range and 2 amps on the high voltage range.EDIT: I just realized that the primary is 240VAC for this transformer.

author: Jwillis
author_rank: Super Contributor
timestamp: March 25, 2019, 10:10:44 pm
content: Transformers are quickly being replaced by Switch mode power supplies.Especially in Europe (as I understand) because their not as efficient as a SMPS. So finding them In the junk pile is getting harder.

author: Benta
author_rank: Super Contributor
timestamp: March 25, 2019, 10:38:46 pm
content: I cannot imagine anyone having a problem finding a 230/24 V, 3 A transformer. It's one of the most common sizes around, plentiful everywhere.You're looking in the wrong places.

author: Zero999
author_rank: Super Contributor
timestamp: March 25, 2019, 10:54:36 pm
content: https://hr.rsdelivers.com/product/rs-pro/st190553/2-output-toroidal-transformer-120va-24v/1176056

author: Cliff Matthews
author_rank: Unknown
timestamp: March 25, 2019, 11:02:44 pm
content: http://www.trafox.hr/Funny, I had never seen Google hide just one house before (or is it a business?)

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 25, 2019, 11:30:10 pm
content: If you can get to Hobart AUI have 10 of what you probably want. Just saved them from the tip 30 minutes ago.

author: soldar
author_rank: Super Contributor
timestamp: March 26, 2019, 08:43:17 am
content: Quote from: chiken on March 25, 2019, 09:41:40 pmEurope is quite big. In my part of Europe there were a lot of 12V halogen lights which are now being replaced with LEDs and the old transformers can be found for free. I have built a power supply using two of these connected in series.Other than that, as has been said, 24 V is extremely common and available pretty much anywhere.Quote from: Cliff Matthews on March 25, 2019, 11:02:44 pmYou only have to ask them and they will do it.

author: Zero999
author_rank: Super Contributor
timestamp: March 26, 2019, 10:00:49 am
content: Quote from: soldar on March 26, 2019, 08:43:17 amBe careful, some are electronic halogen lamp transformers, work at a much higher frequency, than the mains. They consist of a Royer oscillator driving a small ferrite core transformer and are completely unsuitable for most electronic projects. Connecting two 12V units in series will probably not give 12V, more likely smoke.http://electronix.org.ru/datasheet/Motorola/mos/ar609rev0.pdfAs far as LED lighting is concerned: there's no need to rip-out the transformers, as 12V LED lamps which retrofit halogen ones are widely available and some are even compatible with electronic transformers. Here's some information about them and how they work.http://www.p4c.philips.com/files/8/871829112829800/871829112829800_col_eng.pdfhttp://www.ti.com/lit/ug/snvu112/snvu112.pdfhttps://datasheets.maximintegrated.com/en/ds/MAX16840.pdf

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2019, 11:38:28 am
content: If OP can find a couple of MOT's, knock out secondary and series-wire primaries for a little extra PSU grunt (cool running too). Just grab some wire and wind-in whatever secondary you need..

author: soldar
author_rank: Super Contributor
timestamp: March 26, 2019, 11:39:46 am
content: Quote from: Zero999 on March 26, 2019, 10:00:49 amBe careful? Who? Because I assume someone who is looking for a mains transformer knows what a mains transformer looks like and can tell the difference between a mains transformer and, say, a can of tuna.But, OK, I will add a disclaimer to my previous post: Do not go looking for mains transformers if you cannot tell the difference between a mains transformer and a can of tuna.

author: Zero999
author_rank: Super Contributor
timestamp: March 26, 2019, 11:51:42 am
content: Quote from: soldar on March 26, 2019, 11:39:46 amNot you of course, but the original poster. Someone who can't find a 24V transformer, might not know what one looks like. Don't forget this is the beginners section!

author: mariush
author_rank: Super Contributor
timestamp: March 26, 2019, 12:17:50 pm
content: There'sFarnell :https://uk.farnell.com/c/transformers- filter further by Isolation Transformers and Toroidal Power TransformersNote that there's an "official distributor" for Croatia : Altpro D.O.O - seehttps://export.farnell.com/export-portalor just tryhttps://export.farnell.com/RS Components - they have a Croatia sub-site:https://hr.rsdelivers.com/Seehttps://uk.rs-online.com/web/c/power-supplies-transformers/transformers/- filter further by PCB transformers , chassis, toroidal ...TME.eu - good Polish company, should ship to Croatia :https://www.tme.eu/en/katalog/transformers-and-ferrite-cores_100440/Also, should be more clear about exactly what you need.Do you need 24v AC or 24v DC (after rectification using a bridge rectifier, linear regulator etc) ?Transformers have a VA rating ...IF you need 24v AC , like for example to light a 75w incandescent lightbulb, then you could go for a 75VA transformer.if you want to convert output to DC by using a bridge rectifier, then you can approximate the DC voltage and DC current with the formulas:Vdc peak = sqrt(2) x Vac - 2 x Vdiode = ~ 1.414 x Vac - 1.5vCurrent DC = ~ 0.62 x Current ACCapacitance required = Current / 2 x AC frequency x [V dc peak - Vdc min]So for example, if you have a 24v AC transformer with a 100VA rating ( 100VA / 24v = 4.16A) then you'll get a DC voltage with a peak close to 1.414 x 24 - 1.5 = 32v peak and current would be ~ 0.62x4.16 = ~ 2.6AYou'd need C = 2.6 / 2 x 60Hz x (32v - 24v) = 2.6/960 = 0.002708 Farads or ~ 2700uF 50v minimum to keep the DC voltage above 24v at all times.So if you want a voltage up to 32V DC (depending on how big your smoothing capacitor would be) and up to 3A, you'll need more than 100VA...

author: exe
author_rank: Unknown
timestamp: March 26, 2019, 01:00:02 pm
content: If you go with a transformer, be sure to de-rate it properly (for capacitive load it's about 50% derating is comonly accepted), and take into account mains voltage variation.

author: chiken
author_rank: Contributor
timestamp: March 26, 2019, 10:17:39 pm
content: Thanks everyone for response,No need for worrying about safety, i know it allI dont need it urgently, so i just asked here if anyone is sure that know where i could find transformer so i dont have to go around and salvage everything and nothing...Well i thought if nothing, i will modify my microwave transformer, even thought it would be an overkill, but if no other solution...But i was bored and tried to connect microwave transformer backwards(mains on secondary-high voltage), and guess what, output is now 24V... who would thought hehe, but SECONDARY windingsresistance in OHS is 200 OHM, unfortunately dont have inductance-meter, so cannot calculate impedance,And since i did not have too much experience with transformers, what do you guys think?

author: Cliff Matthews
author_rank: Unknown
timestamp: March 26, 2019, 10:45:37 pm
content: Ha, last time I knew that much was 40-years ago..

author: chiken
author_rank: Contributor
timestamp: March 26, 2019, 10:48:51 pm
content: Forgot to say, does anyone know what could be inductance of secondary coil, so i could calculate impedance?

author: soldar
author_rank: Super Contributor
timestamp: March 27, 2019, 12:32:27 pm
content: Quote from: chiken on March 26, 2019, 10:48:51 pmThat is very basic to measure and compute. Connect direct to the mains and measure current. Now connect it with a resistor in series and measure voltage and current. Now take a sheet of paper, scratch your head and start to compute.