11. HOW TO MEASURE THE LEAKAGE INDUCTANCE
by sam Belkin, MSEE
Leakage inductance Ls1 as well as Ls2 may be measured as shown in Figure 5. Shorting of non-measured coil must be done with thick, low resistance wire, especially for the secondary coil.
Figure 5. The measurement of the leakage inductance Ls.
When the value of leakage inductance is obtained, its resistance can be calculated from a very easy formula:
XLsn = 2 x p x f x Lsn.
Supposed that we measure Ls1 = 22.5 m H = 22.5 x 10-6H. Then its resistance at 60 Hz will be
XLs1 = 2 x p x f x Ls1 = 2 x 3.14 x 60 x 22.5 x 10-6 = 8.48 x 10-3 Ohm.
Definitely, such low leakage inductance resistance XLs1 is negligible in comparison with R1= 444 x 10-3 Ohm of the primary circuit resistance from the previous example. However if the leakage inductance will be about 0.5 mH (5 x 10-4 H), its resistance will be about 0.2 Ohm and certainly will affect the primary current.
© Digiweld 1999