Some hobby project uses E or Round type of ferrite transformer which are found in the HV driver circuit. As this is uncommon or a standard type item, i like to know how to self made one, i don't understand why the primary and secondary winding use different wire size ? and how to select the size or shap of the ferrite core for optimal result ?Could any person help me in this. Thanks in advance. Regards
This would be a horrendously challenging project for a newbie. Your best bet would be to find one that you can sacrifice, and dissect it, to see how it's done - this would also yield a core that you know will work at the frequency of interest.
Different current-carrying capability.
This is a whole field of study; even some experts don't know the black magic involved here.
Your best bet would be to go to a library and look for books on transformer design, or maybe google for something similar. I don't know if anyone around here would be willing to take on such a big task as teaching you about ferrites and such, over USENET.
If you're seriously interested in it, signing up for a formal school class would be the way to go.
Good Luck! Rich
It would be helpful if you better described the particular application. These types of transformers are used from audio frequencies thru several hundred MHz.
I don't know what you mean by "round". If you mean torroidal (do-nut shape) then yes they are quite common. You may have to look harder for bars of the material, but I don't really know that for sure. The secret to these things is the composition of the material making them up. They may all look the same, but the materials making them up vary quite a bit. Usually iron powder and other magnetic metals are combined with ceramics in a proprietary mix depending upon the application. Some materials enhance the inductance very little, while some have tremendous effect. Again in RF applications, this makes it possible to create coils for low frequency HF and not have to use hundreds or even thousands of turns of wire. Some core materials have so much inductance that they are pretty much only good for making RF chokes, like you see on monitor cables etc...
It may be for current capacity reasons or space reasons. In RF applications transformers are typically wound with the largest wire that will fit the core to keep resistance to a minimum. This enhances the Q factor of the coil and also reduces self heating. I'm sure there are probably other reasons as well.
Do-nut shaped cores are nice because they are "self shielding". This is nice in RF applications because it keeps the signals where they belong better.
Because the size of the wire is related to the current. If it's a step-up transformer for example, the secondary current is lower than the primary current.
Learning transformer design is not a trivial (easy) task ! Some aspects of it are quite straighforward but the detail is complicated.
Graham
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