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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Lets say I have a transformer on a flyback core with for example 25 primary and 1000 secondary turns, windings opposite each other, no airgap. How do I calculate the primary leakage inductance (with sec. shorted)? Can anyone provide at least a ballpark figure, I don't have a LCR meter to check it.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
You need to know the permeability of the core so that you can determine its reluctance. From there you can figure out the coupling coefficient. But, without knowing the permeability spec on your core, there is no hope, and from what ive experienced the leakage inductance can vary to a large degree depending on the type of ferrite.
Do you have a scope? You can get creative and drive the primary with a pulse generator and look at the primary current (shorted secondary) and use the relation that V = L*di/dt. You know V (or can measure it) and it should be constant. L is assumed constant too, so you *should* see a linear rise in current (di/dt = constant). This is provided you dont saturate the core (at which point L is not linear), and that your secondary reflected impedance isnt too capacitive.
You should find the di/dt is much larger as you open the core's gap.
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Leakage inductance
