T
Still incomplete drawings. Where's the return path?
I don't ask for the function of the current transformer, I'm asking for actual geometry.
I don't see what's the point of distinguishing transformer leakage and wiring inductance. Electrically they are indistinguishable.
More a question of principle arrangement than exact layout files. But anyway, this sight "effectively cancels" my ability to continue the discussion.I would have to send the PCB layout file for people to see the full primary current loop. In any case, it is the same in each case of the example pictures, so effectively cancels the requirement to see it exactly.
Well I thank yourself for your opinion stated a few posts back. I am trying to find corroborative literature to this, but cannot. I tend to entirely agree with yourself here though, it just kind of makes good sense.As a result, you'll get the lowest leakage with the secondary winding concentrated under the primary loop.
which of the following two CST's has more leakage inductance, as seen from the primary?...the one with the primary and secondary bunched together, or the one where the secondary is spread evenly around the torroid core?
View attachment 120790
But after this statement, I fear that have made a wrong assumption...I am wondering if the twisting can possibly reduce the leakage inductance seen from the primary of the CST
Twisting a two wires doesn't reduce the wiring inductance as such
It's right. But, in a typical two-wire the wire distance is too low to get a considerable inductance reduction. You get about the same nH/cm number for a twisted or untwisted pair.Therefore, the final inductance as a sum of each field, should be reduced.
That’s not right ?
Twisting the wires is much more effective at reducing mutual inductance between the pair and other circuits at moderate distances away (farther than the twist spacing).
Thing is, if the loop area is large, you are probably stuffed whatever CT you use, high power switcher layout is ALL about minimizing current loop areas.
I recommend picking (or specifying) a part that meets the required spec and not worrying too much about how the part manufacturer gets there as long as they do meet spec.
The nice thing about this approach is that you as the design engineer do not need to be a magnetics design and magnetics DFM guru (Transformer companies have those guys), you can treat the details of core behavior and winding methods the same way you treat the silicon lattice constants when you pick a chip (Interesting, but fundamentally somebody elses problem).
Regards, Dan.
Likely because it's a common mode choke, and uses a very high permeability core with no gap. The same can't be applied to an inductor used for energy storage.In relation to this, if we look at the datasheet for the 81xx-RC series of common mode chokes, (by Bourns) we can see that in actual fact, having primary and secondary totally separated from each other, on either side of a torroid, still gives amazingly good primary to secondary coupling.
In relation to this, if we look at the datasheet for the 81xx-RC series of common mode chokes, (by Bourns) we can see that in actual fact, having primary and secondary totally separated from each other, on either side of a torroid, still gives amazingly good primary to secondary coupling.
The coil inductance is 2.4mH and the leakage is 9.4uH. That's a leakage of 0.998 coupling.I'm afraid the above might be misleading to newbies, amazingly good? what is that? coupling of 0.999? more likely the leakage is 15-20% of the inductance in one coil, this fact is exploited by designers of mains filters to give differential impedance...
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