Electronic – (How) can I determine the characteristics of an unidentified SMPS transformer?


I have torn down a crappy Antec Neo HE power supply that would turn on randomly only. It's rated 430W, amongst these 3.3V/22A, 5V/14A, 3 x 12V/16A.

I'm planning to use it for parts in a home made power supply project. There is an unidentified transformer (marked VRL35W015 on its top, SBI 4.2 E150436 C on its side) which I'd like to know how I can check its features, e.g. frequency range, max current, voltage and whatnot. The SBI 4.2 marker lead me to a Taiwanese company that does unfortunately not publish the specification for that transformer type.

Apparently the transformer has two primary and two secondary windings.
How can I check the characteristics of this transformer? Is there a typical circuitry I can build to check it out?

EDIT: Actually the only code that is specific to this transformer is VRL35W015. SBI 4.2 and E150436 seem to be reference model or something similar. There is a small transformer next to this one, both share the same SBI 4.2 and E150436 but the smaller one has a different identifier: VEE19FRC9.

This transformer also has 6 pins on the secondary, wired together in adjacent pairs on the PCB, the primary four pins, independently connected. The document pointed to by Andy Aka seems to confirm, like the hinted thread, the fact that this transformer has been specifically designed for this Antec Neo HE. Not any reason to ditch this transformer, to me of course.

I will observe (frequency, voltages and apparent ratios) with my oscilloscope how the transformer behaves. This will hopefully give me basic information, which I'll further use in my "quest". Lot of fun ahead.

Best Answer

Yes it's possible to extract the characteristics of an unknown flyback transformer. But as @FakeMoustache said, it can be an expensive proposition. Basically you need a network analyzer. Here is a tutorial on using one to determine the lumped-element characteristic of an "unknown" flyback xfmr. Note that they still assume known the turns ratio... and the model they get is still not quite matching the xfrm at very high frequencies.

You might also want to read chapter 21 of Transformers: Analysis, Design, and Measurement on ways to basically do all those measurements separately. There are a lot of parameters to determine.

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