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which has the biggest leakage inductance as seen from the primary?
thanks, I will try, but the primary carries 20 Amps of current, so it wont be easy to twist, but it seems a good idea.Are you willing to twist both sides like that ?
The loop spanned by the primary conductor definitely matters. Lack of the return path creates a partly unspecified geometry in your drawing.I presume that the fact to do not twist the wire right after the winding, this would produce a most significant leakage inductance if compared to other effects nearby the core.
andre_luis wasn't talking about this point at all. In my view, the left uneven winding geometry gives a slightly higher leakage inductance. The right evenly spaced winding is better but not necessarily optimal. As previously mentioned, a single turn is asymmetrical by nature (unless you have a coaxial return). As a result, you'll get the lowest leakage with the secondary winding concentrated under the primary loop.so I believe you are implying that to reduce leakage, the secondary must be evenly spread right round the whole torroid circumference?
the loop of the primary is the mosfet loop of the boost pfc stage.....the CST is in the drain connection of the boost pfc fet, so the loop of the primary is through the input capacitor (1uF) , then through the boost inductor, then through the CST primary, then through the fet, then back to the input capacitor. Is this going to mean loads of leakage unless I put in the twist as shown by Andre Luis?The loop spanned by the primary conductor definitely matters. Lack of the return path creates a partly unspecified geometry in your drawing.
Is this going to mean loads of leakage unless I put in the twist
Would you agree that it is too risky to get SMPS current sense transformers wound onto ETD type bobbins? After all, if the winders forget to actually cross the primary wire back over itself then the primary may have zero coupling with the secondary, as the attached shows.
As you know, this can't happen with toroid cores since the winding is taken through the centre of the toroid, and therefore, there is always a completed turn of primary coupling up with the secondary.
So do you agree that its best not to wind current sense transformers on ETD type bobbins?
In the attachement, the winder has wound the primary round the bobbin in both cases, but in one picture, it doesn't end up forming a whole turn round the bobbin, which is bad.
Basically yes. Presumedly you can't "twist" the primary circuit completely, but reducing the area spanned between forward and return current path is essential for a low inductance design. Implementing the wiring as superimposed PCB planes, or even as a sandwich of multiple interleaved planes are examples how at least part of the circuit can be made with very low inductance.the loop of the primary is the mosfet loop of the boost pfc stage.....the CST is in the drain connection of the boost pfc fet, so the loop of the primary is through the input capacitor (1uF) , then through the boost inductor, then through the CST primary, then through the fet, then back to the input capacitor. Is this going to mean loads of leakage unless I put in the twist as shown by Andre Luis?
..at first we just need a few prototypes, and no manufacturer will do such low volume for us, we have to do it ourselves, there is nothing "in stock" off the shelf at this high current level (39 Amps peak, 26 Amps average)For a mature transformer factory, they shoud have mature manufacture technology, e.g. test turns and inductance value and Q value, they can find the faliure part by these testing proceses, so no problem
As such, in the attached diagram, which Current sense transformer (CST) has the most leakage inductance, as seen from the primary?
-thanks, I agree that the stray wiring inductance of the picture on the Left hand side is greater than in the right hand side one. However, which one has the most transformer leakage inductance, as seen from the primary?the first picture would produce a higher stray inductance along the wire pair
Still incomplete drawings. Where's the return path?which Current sense transformer (CST) has the most leakage inductance, as seen from the primary?
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