transformer selection for 250w  inverter - Page 1
Forum section: electronics / projects

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 03, 2020, 01:57:26 am
content: i want to get an ei transformer for a hbridge driven invertermy doubt is for 250w 9,0v to 220v transformer what current needed?for centertap design i understand 1/2 *(250/9)x0.15Amp is approximate current.1/2 because twocoils in CT.So for HBridge invi with one coil,what is current needed assume15% loss.also why there are many voltages in Ups trandformerslike 190 ,220,230

author: Zero999
author_rank: Super Contributor
timestamp: February 03, 2020, 10:57:31 am
content: Please provide more information. What's an ei transformer?The losses in transformers are primarily voltage, rather than current. The fully-loaded secondary voltage is lower, than the turns ratio, because of the voltage drop associated with the resistance of both primary and secondary windings. The current loss is an extra current being drawn due to the eddy and hysteresis losses and is relatively small.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 03, 2020, 01:23:25 pm
content: E I iron core.not ferrite . so to get a good performancewhat will be amp rating if we use 0-9v highcurrent side

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 03, 2020, 01:32:33 pm
content: Pretty much every inverter transformer I have come across was custom made for the application.Quote from: dave_j_fan on February 03, 2020, 01:23:25 pmYou won't be able to use a particularly high PWM frequency with laminated iron cores, there's a reason every modern 250W inverter uses ferrite cores. There's also powdered iron cores and amorphous iron cores, but there's no savings using those for a 250W inverter.

author: Zero999
author_rank: Super Contributor
timestamp: February 03, 2020, 04:47:27 pm
content: Oh, I see, the all lowercase confused me.I believe he wants to use a low frequency power transformer, like an old school inverter. The problem is he also wants it to be cheap. A low frequency transformer is not a cheap option, which is to use a high frequency ferrite transformer, running at a much higher frequency and a rectifier and filter, to make a DC:DC converter, followed by an H-bridge to make an inverter. The extra cost of the more complex electronics will be outweighed by the smaller, lightweight transformer.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 04, 2020, 03:28:53 am
content: i get in 9$ for EI transformer 600vaeconomics is worked upon .i want tomake old style inverter .made circuit in 2$ tested onunknown transformer(current unknown)no high freq as we are not yeat expertin ferrite.can any one give approx current rating

author: Zero999
author_rank: Super Contributor
timestamp: February 04, 2020, 02:01:17 pm
content: Quote from: dave_j_fan on February 04, 2020, 03:28:53 amIs that a, new genuine 600VA continuously rated transformer or secondhand/fake/stolen?A genuine mains frequency 600VA transformer weighs around 8kg. The cost of the raw materials, which typically make up 50% of the price, is more than 9USD. I could probably get more than that, per non-working 600VA transformer, if I took a large quantity of to a scrapyard.https://www.copper.org/environment/sustainable-energy/transformers/case-studies/transformer_manufacturer_a6100.htmlhttps://www.lme.com/en-gb/metals/non-ferrous/copper/#tabIndex=0https://docs.rs-online.com/9bd6/0900766b81546529.pdfQuoteFerrite will be cheaper: less copper and steel.I doubt you'll find an off the shelf transformer which will meet your requirements. You'll get just half the rated power for a centre tapped transformer and you won't find a 9V-0V-9V unit rated at 400VA.If labour is cheap, then it might be worthwhile rewinding ferrite transformers from old computer power supplies and using a DC:DC converter and H-bridge, as mentioned before.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 04, 2020, 05:11:29 pm
content: it all depends on where u livehere Ups with 600va is just 18$(please i have supplier he will do as per my need, kindly i request not to suggest me on ferrite or smps rewindingplease please please 😑)now please dont suggest buy ups and go home .if respected person knows current rating for 250w pleasesay with some approximationor there is no use here😓😓😓attached an image 2.5inx4inch transformer i got for 8$freshly made.it is Ct.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 04, 2020, 05:16:38 pm
content: Quote from: NiHaoMike on February 03, 2020, 01:32:33 pmiknow but dont want to go into experimental circuit.i have very nice working HBridge circuit.this year i willmake couple of EI transformers.with real small circuit.the High freq model i wilmake later.my fabricator is free for few days so need info immediately.once he gets big orders he willnot make smaller qty.

author: Zero999
author_rank: Super Contributor
timestamp: February 04, 2020, 10:07:44 pm
content: Quote from: dave_j_fan on February 04, 2020, 05:11:29 pmWhilst the price of labour varies widely, raw materials not so much. Copper and steel will be a similar price in India, to any ware else. If you happen to be near a smelting plant, then they might be a little cheaper, but not much.QuoteThat's because it will use a ferrite transformer!And it will probably not be rated for 600VA continuously.QuoteWhy don't you ask your supplier?You need a 250VA transformer, with a 9-0-9V primaryQuoteThat won't be rated to 600VA. It'll be useful for 60VA maximum, continuous rating.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: February 05, 2020, 07:07:49 am
content: i got it.. someone will makeme go 😇😇i will wait till some sincere member will answerme on the query.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: March 01, 2020, 02:11:14 pm
content: i have got the transformer with 45Amp winding220v winding is copper45Amp is aluminum alloy.matches economics.cost was 9$