I have shorted all secondary windings at a single point. When measured from primary it was around 45uH with a gap of 0.57mm. However when I removed the gap and then measured, it was around only 15uH. So which one is true leakage inductance?You would short all three outputs to measure the input leakage inductance.
They can all be shorted to the same point or shorted separately, but all be shorted at the same time.
If they are not all shorted than you may see a somewhat higher primary leakage inductance.
Not sure how the gap will affect the leakage inductance, but I would expect to be less.
I agree that the values sound surprizing. Either it's an effect of a special winding geometry or the LCR meter has problems. Can you show a sketch of the winding geometry?I still wonder then why my LCR meter is measuring leakage as 45uH with gap and only 15uH without gap when measured from primary side.
I'm using,I agree that the values sound surprizing. Either it's an effect of a special winding geometry or the LCR meter has problems. Can you show a sketch of the winding geometry?
@cupoftea & @FvM plz attached here find the transformer winding geometry that I used.Can you just do a simple diagram, that will show whether you have whole layers or not?.....or do you have one coil on the RHS, and the other coil on the LHS, like in a sectioned bobbin?
What is your upper resonant frequency in the LLC?......short the secs, then hit the primary with a square wave of that frequency, then tune the capacitance till you get max amplitude.....then you are on resonance.......then you can calc the leakage inductance, and you are doing so at exactly your intended switching frequency, so it cannot possibly be a wrong value....that is the best measurement of leakage inductance that you will get.
Page 10 (AKA page 12) of this shows leakage inductance vs gap length for an llc transformer with the shown winding geometry.
Typically Ls decreases with increased air gap, also in the linked Onsemi LLC application note. With unusual winding geometry, the relation can be different. The reported 45 uH versus 15 uH relation doesn't sound reasonable and might indicate a measurement artifact...i dont think anybody disagrees that leakage inductance increases with air gap...it does..
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?