Datasheet

AN3180 Measuring transformer and coupled inductor parameters
Doc ID 17273 Rev 1 37/39
Figure 30. Winding connections: aiding flux (left), opposing flux (right)
It is always L
A
> L
O
, therefore, as already mentioned:
Equation 32
The advantage of this method is its low sensitivity to winding resistance and to the
impedance of the wire used for connecting the windings. It is not recommended for low
values of k because in that case it would be given by the difference of two similar quantities,
and the error might be high.
Whichever method has been used, the parameters of the equivalent circuit of
Figure 25 (a =
n, assuming n is known) can be readily calculated from the third group of Figure 26 with
obvious symbolism change:
Equation 33
The parameters of the equivalent circuit of Figure 26 (a = n
e
, useful in case n is not known)
are given by
Figure 28, here re-written for convenience:
Equation 34
!-V
/ //0
$  


/

/

0
/

/

0
/ //0
2 
21
OAOA
LL4
LL
k
4
LL
M
−
=⇒
−
=
⎪
⎪
⎪
⎩
⎪
⎪
⎪
⎨
⎧
−=−=
−=−=
=
MLLnLL
M
LLLL
M
L
2M
2
22
1M11
M
n
n
n
l
l
(
)
()
⎪
⎩
⎪
⎨
⎧
=
−=
=
−=
μ
1
2
2b
1
1a
L
L
with,
Lk1L
LkL
Lk1L
e
n