from Hacker News

Practical Transformer Winding (2010)

by bearbin on 12/25/21, 5:50 PM with 36 comments

• by myself248 on 12/27/21, 2:36 PM

  Yesss! This is what I was hoping to find last time I clicked on an HN headline "transformers from scratch", which turned out to be about machine learning: https://news.ycombinator.com/item?id=29280909

  This is great. It gets into the flux density and iron loss calculations that affect the physical size of a transformer core, choosing the wire, and then exquisite detail of actually winding and finishing the thing.

  I need to spend a bunch more time reading this site.

• by hwillis on 12/27/21, 3:36 PM

  Ludens is absolutely legendary. This is part of his micro hydroelectric dam[1], which he uses to power his house, which he of course built himself.

  Far different, but if you enjoyed this you may also enjoy another classic (which does not have explanation), Claude Paillard making a vacuum tube from glass and metal: https://www.youtube.com/watch?v=EzyXMEpq4qw

  [1]: https://ludens.cl/paradise/turbine/turbine.html

• by Isamu on 12/27/21, 4:58 PM

  > Transformer steel is not all born alike. Manufacturers will provide data sheets about their products (often on their web sites), where you can see what they offer. There are usually many grades, with vastly different loss characteristics. At a given flux density and frequency, a good material might have ten times less loss than a cheap material! So it pays to look, investigate, and decide intelligently what to buy. Thinner sheets normally have lower loss, and the rest of the secret lies in the exact alloy.

  Okay this is what I come to HN for, thanks everybody!

• by GnarfGnarf on 12/27/21, 4:00 PM

  I ran a high school science lab in Bolivia in 1968. It was cheaper to get a local guy to hand-wind forty centre-tap transformers, than to order them from Germany or the U.S.

• by VBprogrammer on 12/27/21, 3:39 PM

  There are interesting people on thebackshed.net who have been building whole house inverters, initially repurposing some Chinese inverter chip but more recently an arduino for the brains. Unfortunately a lot of the info is spread across many different build threads but a big part of it is about rewinding toroidal transformers.

• by Animats on 12/27/21, 8:38 PM

  That's so retro. Useful if repairing boat-anchor equipment from the 1950s.

  Here's a more modern video on winding toroids by hand.[1]

  [1] https://youtu.be/sDIWNHOoNh8

• by londons_explore on 12/27/21, 6:13 PM

  Nearly all usecases for a power transformer are now better served by a switched mode power supply.

  They tend to be much smaller, lighter, more efficient, cooler and cheaper. They also have features like adjustable output voltage, current limits, and overheat protection. Some can input and output AC or DC, at a configurable frequency and sometimes waveform. Some offer the same galvanic isolation that a transformer offers too.

  The core of a switched mode supply usually is a transformer, or at least an inductor, but the key difference is that it operates at far higher frequencies than classic uses of transformers, which allows them to be far far smaller, and therefore cheaper for the same power output.

• by aivisol on 12/27/21, 3:05 PM

  Winding your own transformer was one of those things which amazed me as a teenager: you do a simple math by calculating winding ratio and the voltage is changed at the secondary by magic...

• by bserge on 12/27/21, 7:56 PM

  Christ, I still have a welder that I made myself. It uses a round ferromagnetic core I found in a scrapyard.

  I forgot how many windings it has, I think around 300 on the input side and 40 on the output.

  Wiring it was a major pain in the ass, as the core is round, a closed circle.

  And it draws too much current when idle, which means I have not used enough wire on the input side or the core is too small, fuck knows, I was 14 when I made it.

  It does weld well, especially on DC through 4 huge diodes I also found in some scrap.

  Sorry for my English, I'm drunk and tired.