Transformers

Basics

Calculating Number of Turns, Core Size, and Wire Needed

N&V 2020-5. Tech Forum, there are some equations and a chart. See the example given. Also consider starting with an existing transformer, keeping the primary and rewinding only the secondary.

Tips/Techniques

Measuring Capacitance between Windings

There are expected values. Consider the capacitance may differ based on frequency per Capacitors. See: https://www.eevblog.com/forum/chat/custom-r-core-transformers-on-ebay/ This thread also links to a few places where you can buy custom made ones.

Hi Pot testing

breakdown voltage of the windings. For 120V mains transformers it's around 1200Vrms (maybe i think 1500V). See https://www.youtube.com/watch?v=NhWkxIBGkCM Lots of youtube videos on hi pot testing. /archive /2023_03.

Faraday Shields

They can be built different ways, connected to different windings

• https://canadatransformers.com/faraday-shield
• http://web.archive.org/web/20240228180910/https://canadatransformers.com/faraday-shield/

Disassembly Should Not Destroy Them

separating them, then reassembling should not destroy them if done properly. Use a proper measuring tool (calipers, micrometer) to get the before disassembly and after disassembly distance between the cores.

• https://www.eevblog.com/forum/projects/heated-ferrite-useless-ferrite/
• https://electronics.stackexchange.com/questions/497489/temperature-degradation-of-ferrite-cores

Mention of diodes gone wild. When in doubt of the before / after performance, make some measurements.