# Pulse transformer

#### Coucou80

Joined Apr 7, 2018
59
Is there any material that exist where I can learn how to read marking on pulse transformer?
For example I see a couple of transformers with the “YDD” marking followed with a couple of letters and numbers. What YDD marking stand for to begin with. I’m just looking at understanding the nomenclature so I can start sorting them up. Not knowing their properties is very disapointing and they will most likely end up in the garbage can. Yes I can test for their resonance point with a function gen and oscilloscope, but that doesn’t tell me much on the core properties.
Thank you for the help once again

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#### crutschow

Joined Mar 14, 2008
32,932
Try inputing a pulse or square-wave of various frequencies, pulse width, and amplitude while monitoring the output.
That will tell you the limits for the saturation of the core.

#### Coucou80

Joined Apr 7, 2018
59
…but that is what I’m doing to find out the resonance frequency. Varying frequency until amplitude is at its maximum. How would you find core saturation limit this way?

#### eetech00

Joined Jun 8, 2013
3,430
…but that is what I’m doing to find out the resonance frequency. Varying frequency until amplitude is at its maximum. How would you find core saturation limit this way?
The output waveform will begin to distort and the amplitude will decrease. The output should be under load while testing.

#### Coucou80

Joined Apr 7, 2018
59
So once I have that frequency, how would that give the max flux density of the core for say?

#### crutschow

Joined Mar 14, 2008
32,932
So once I have that frequency, how would that give the max flux density of the core for say?
You would find the saturation V*t (input voltage times time) value before the output is distorted, which is typically how pulse transformers are rated.
Why do you want to know the max flux density?

#### Coucou80

Joined Apr 7, 2018
59
To know the specs of the core and rewind it for something else eventually.

#### Irving

Joined Jan 30, 2016
3,496
The YDD etc is a manufacturers part code... you need to figure out the manufacturer and get the datasheets. Give an example part code...

#### crutschow

Joined Mar 14, 2008
32,932
To know the specs of the core and rewind it for something else eventually.
Then you would need to know (or count) the number of primary turns.

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#### Coucou80

Joined Apr 7, 2018
59
The YDD etc is a manufacturers part code... you need to figure out the manufacturer and get the datasheets. Give an example part code...
As requested.
So how are we suppose to interpret that ?

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#### Coucou80

Joined Apr 7, 2018
59
Anybody can assist in decripting the above nomenclature (aside from the fact that it is made in china…)
The more I read and experiment with pulse transformer, the more I realise that there is alot of approximation and trade offs when designing one. Yes there are formula that provide the amount of turns for the primary winding, such as :
Npri = Vin * 10^8 / ( 4 * F * Bmax * Ae )
but still, finding Bmax is a hell of a challenge from my perspective :/
Thank you.

#### Irving

Joined Jan 30, 2016
3,496
As requested.
So how are we suppose to interpret that ?
With some difficulty... but experience and some Google-Fu suggests this is a custom transformer, possibly designed/manufactured by Shenzhen Elemay Electronics Co. The BCK-80 appears to reference the core size but data isn't readily available. You might be able to get more info from them but I doubt it. The other numbers might be equivalent(s) from other supplier(s) or the end user's internal part # or even the contract #, all are possible.

That specific transformer is listed here as the main SMPS transformer for a Hyundai TV, which backs up my view that its a custom job.

#### Coucou80

Joined Apr 7, 2018
59
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#### Coucou80

Joined Apr 7, 2018
59
With some difficulty... but experience and some Google-Fu suggests this is a custom transformer, possibly designed/manufactured by Shenzhen Elemay Electronics Co. The BCK-80 appears to reference the core size but data isn't readily available. You might be able to get more info from them but I doubt it. The other numbers might be equivalent(s) from other supplier(s) or the end user's internal part # or even the contract #, all are possible.

That specific transformer is listed here as the main SMPS transformer for a Hyundai TV, which backs up my view that its a custom job.
Thank you sir,
So in this case, is worth keeping the core for another project or would that be impossible, because of the unknown data related to the core caracteristics?

#### Coucou80

Joined Apr 7, 2018
59
I just found this catalogue list from Magnetics. It is dated from 2013, but I think it provides good information at the end of the document (page 63 of the document and not the reader) on what to consider when choosing a core depending on the topology. I’m sure some of you have already seen this. I thought I’ll just put it up there.

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#### DickCappels

Joined Aug 21, 2008
10,068
Thank you sir,
So in this case, is worth keeping the core for another project or would that be impossible, because of the unknown data related to the core caracteristics?
That is bordering on being HERETICAL! You never know whether a part you cannot imagine using today won't save your project in a few years (or decades). Any ferrite core has potential future use and for some of the uses, you don't need to know much about the core to make some use of them.

#### Irving

Joined Jan 30, 2016
3,496
Once you have dismantled the existing transformer it should be possible to ascertain key physical parameters. Eg, wind a known number of turns of wire on the core and use an LCR meter to measure the inductance; that, together with the core dimensions will give you an idea of the relative permeability and therefore the material. It should then be possible to compare that info with various manufacturer's published data to identify a core similar to yours, at least near enough to use for design purposes.

Another thing you can do is create a tuned circuit and see how the frequency response, and therefore the inductance, changes with static current in the inductor which tells you something about the core saturation parameters.