# What is the meaning of below notations in flyback/forward transformer datasheets?  Flyback / Forward transformer datasheet

How can I decipher the above diagrams?

1. Does the inductance value represent magnetizing inductance?
2. Why are there 2 windings (1-3 and 2-4) at primary side of flyback converter? What is meant by turns ratio 1.14? Which winding does it denote?

Does the inductance value represent magnetizing inductance?

The primary inductance value does represent the magnetization inductance.

Why are there 2 windings (1-3 and 2-4) at primary side of flyback converter?

This gives you the option of them being in series or being in parallel thus making the transformer suit wider primary voltage applications. When wired in parallel, the net inductance of the two windings remains the same as for a single winding (assuming near 100% flux coupling) but the $$\I^2R\$$ losses will be less. When wired in series, in effect the turns are doubled and, as per standard inductance calculations where flux is strongly coupled to all turns, the inductance will quadruple.

What is meant by turns ratio 1.14?

An example might be 57 turns on the primary with only 50 turns on the secondary because 57 divided by 50 = 1.14. But, 1.14 might just be rounded up or down and the actual turns are lower such as 8:7. This latter scenario is more likely but, it's difficult to tell without more data on the core.

• Iam assuming both primary windings have identical turns and turns ratio is defined for individual primary winding. If secondary ( marked as 1.0) is having x turns, each primary winding will have 1.14x turns, correct? Feb 14 at 9:41
• @DivyaK.S when you see two primary windings like this they have to be identical else, when you wire them in parallel you get an almighty problem; the excess windings on one effectively gets shorted out. Yes, marking one of the windings as "1.0" is fairly standard convention but, it needn't be the secondary; the primary(s) could be marked 1.0 and the secondary could be marked 0.877 for instance. Feb 14 at 9:44