Ferrites - question about inductance

[j_writer]

(Please see post #376043 for background info. Thanks.)

1) How do you measure main inductance of a transformer? Secondary open or loaded or does it make a difference?

2) How does this relate to specific inductance AL? Should L = AL*(N squared)?

 

[FvM]

1. If you look at a transformer equivalent circuit, you'll see that open circuit measurement should give the smallest
error in main inductance measurement.
2. Yes.

 

[eem2am]

AL is the "ALlowance".....it is the inverse of "reluctance"

although i think its been adjusted and your equation gives inductance in nH.

 

[FvM]

AL is the "ALlowance"

I rather see the formula sign derived from it's proportionality to Σ(A/l) form factor.

 

[j_writer]

I know this parameter is very important but I cannot find a good definition on the web. Most often it is written A-sub-L. Further questions...

3) What is meant by a summation of area over inductance? (∑ A/l)
4) Are the units of A-sub-L equal to Henrys over turns squared? (If so, this would account for the name specific inductance which I have seen in some papers.)