Power Supply Transformer Markings

[tedstruk]

I scrapped a powersupply and one of the transformers in it has 4 pins.
assuming it is a buck converter(probably wrong) I examined it very closely...
the red dot on top signifies the output side, I think? and the other end has 2 letters on each side of the coil(maybe mould stamps what ever) S and W.

Am I right about the red dot?
What does the S and W mean?
what is the function to test the input output(is measuring the power in and out of it, the right way to discover the transformers capabilities?)

 

[kellys_eye]

Post pics please.

It's never wise to assume anything about transformers like this - it's always prudent to make measurements to clarify things.

With only four connections we might assume a single winding for both the primary and secondary so you can do a simple continuity check to determine which pins are related to which winding.

To properly reuse the transformer you would need to know its turns-ratio and the specification of the ferrite core - it's 'reluctance'. I'm only assuming this is a ferrite cored transformer from your statement that it came from a buck converter.

Many such transformers are based on industry standard cores and can be deduced from the core measurements (width, height, air gap etc) but sometimes stripping the coil is the only way.

If you do that then you can test for the coil reluctance by applying a known signal level through a known number of turns and go from there.

 

[tedstruk]

heres the pics.

 

[tedstruk]

this one was on the board also....
pesky 9 pinner
SEE THE W on the second pic....
what does S and W mean?

 

[tedstruk]

Here is the pinout for the bottom one... using the cheapest atmega328 capacitor tester...the first reading at A-B is .5 ohms not .04ohms. sorry

 

[ramussons]

Can you give a nice photo of that power supply board - both sides?

 

[73's de Edd]

Sir tedstruk . .
. . .
More importantly, can you give the BRAND and MODEL number of the power supply itself.
I got a blurred pic and no size referencing . . such as to an Amerikanski penny . . .but my bet is that the TALLER transformer is being your standby voltage . . . .power supply transformer.
The smaller transformer being the POWER FET s driver transformer.
( From an oooooooolde 1999 vintage power supply.)

73's de Edd

 

[davenn]

heres the pics.

View attachment 35137

View attachment 35136

OK I'm suspecting that you have pulled apart a switch mode PSU

the inductor above isn't a transformer, rather it is the filter choke out of the mains input section


this one below looks like the main switching transformer

this one was on the board also....
pesky 9 pinner


View attachment 35139

View attachment 35138

 

[kellys_eye]

I concur with the above.

The 'white' transformer is a common-mode choke - filtering the incoming supply.

The 'black' transformer is the actual Switching one - it will have the usual primary (possibly centre-tapped), the secondaries - and there can be multiples of them and (possibly) a feedback winding.

It's usually quite easy to figure out what's what from the pictures of the board it came from (top and bottom please), estimate its power handling capabilities and offer potential re-use value.

Building your own SMPS is a great way to understand them and opens the door to making your own supplies for 'any occasion' but, as usual, technology advances very quickly these days and the ease-of-availabilty buck/boost modules often makes building your own supply a pointless task - other than the valuable learning curve of course.

 

[73's de Edd]

Sir tedstruck . . . .
Looking at the very first photo and at the left front foreground.
The wire terminal has about 22 gauge wire wrapped around it to make connection to it .
If you find the same gauge wire on the other three connections, there should be two like isolated windings that are wound so as to be 180 degree phase inverted.
I see that you did not do an inductance check on that transformers two windings , should you now do so, I expect them to be practically identical inductance windings .
An educated guess . . . as for the Red dot marking is of the unit having passed HIPOT testing. ( H I voltage breakdown testing.)
It's still a toss up on the other transformer, in not having any physical size referencing.
I perceive of it being smaller than a typical main powered transformer, as well, most main transformers are using LITZ wire windings.
Usually there is the hefty main transformer and the separate standby transformer that is usually 1/2 to 1/3 the mains size, and usually taller than you would expect it to be.

73's de Edd

 

[davenn]

Sir tedstruck . . . .
Looking at the very first photo and at the left front foreground.
The wire terminal has about 22 gauge wire wrapped around it to make connection to it .
If you find the same gauge wire on the other three connections, there should be two like isolated windings that are wound so as to be 180 degree phase inverted.
I see that you did not do an inductance check on that transformers two windings , should you now do so, I expect them to be practically identical inductance windings .
An educated guess . . . as for the Red dot marking is of the unit having passed HIPOT testing. ( H I voltage breakdown testing.)
It's still a toss up on the other transformer, in not having any physical size referencing.
I perceive of it being smaller than a typical main powered transformer, as well, most main transformers are using LITZ wire windings.
Usually there is the hefty main transformer and the separate standby transformer that is usually 1/2 to 1/3 the mains size, and usually taller than you would expect it to be.

73's de Edd

I cant even begin to agree with that

maybe you didn't read my and Kellys eye's posts ??

 

[tedstruk]

here are the choke pinout readings...

the other transformer has an center tapped inductor that reads 1.68mH and different center tapped inductor that reads .68mH. Am I to assume that if I put a low power into the .68mH coil, that the 1.68mH coil will be higher in power? I am trying to learn how to use transformers...

 

[davenn]

Am I to assume that if I put a low power into the .68mH coil, that the 1.68mH coil will be higher in power? I am trying to learn how to use transformers...

Ted,
you haven't picked normal transformers to learn transformer basics from

as I said in an earlier post ... you have parts from a switch mode PSU. the AC used in these transformers ( referring to the one in post #4) operates at high frequency
above 40 kHz and often up to several 100 kHz. They are NOT DESIGNED for low freq mains voltage