I have chosen a transformer from We-online type 750032051-1 and I am working on a project that input voltage 1000 vDC and output voltage 24 vDc. I have some inquiries about this transformer: 1- how is it connected? 2- What are the inductance values of all three windings? 3- What is the coupling factor?

If i am not mistaken, the secondary side winding are connected in parallel and the values for praimary winding is 10mH and secondary winding 100µH each. K= coupling factor is 0.994 but I am not sure

  • \$\begingroup\$ How did you choose a part for a flyback converter without knowing the inductance? Link to a datasheet? The numbers you have look wrong (10uH for each primary and 1mH for the secondary). but the -1 is not explained. \$\endgroup\$ Sep 4, 2015 at 21:04
  • \$\begingroup\$ actually i know the inductance before which L1= 1mH and L2= 10µH, but when I choose this transformer the winding on the secondary side are two. , for the 1- I would connect them with the circuit so should I connect them two winding in parallel or in series katalog.we-online.de/pbs/datasheet/750032051.pdf \$\endgroup\$
    – Fadi
    Sep 4, 2015 at 21:19

1 Answer 1


The ratio is 10:1 for one low voltage winding (or two in parallel) to the high voltage winding. (I'll avoid using "primary"/"secondary" since your definition is the opposite of the datasheet).

You have two choices- 10:1 with windings in parallel and 5:1 with windings in series. You probably want the higher ratio.

I get 0.997 for the coupling coefficent:

\$k = \sqrt{1 - \frac{L_{LEAK}}{L}}\$

The inductance of one low voltage winding (or two in parallel) is 10uH. The inductance of the high voltage winding is \$N^2\$ higher, or 1mH.

  • \$\begingroup\$ Thank you for your reply, so for the inductance of one low voltage winding is 10µH, and for two winding in parallel are 10µH (each) ? \$\endgroup\$
    – Fadi
    Sep 5, 2015 at 11:10
  • \$\begingroup\$ Two windings in parallel will also be 10uH (or about 0 depending on how they are connected). \$\endgroup\$ Sep 5, 2015 at 11:16
  • \$\begingroup\$ sorry for lots of question just to be clear i will connect them in parallel so each one has 10µH not both of them have 10µH. \$\endgroup\$
    – Fadi
    Sep 5, 2015 at 12:07
  • \$\begingroup\$ Individually or in parallel they're 10uH. When they're in parallel they're coupled to each other just as if you wound two strands of wire side-by-side. The DC resistance is half. \$\endgroup\$ Sep 5, 2015 at 12:29

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