Ferrite materials used for offline Flyback converter

[treez]

Hi,
We are doing the core loss calculation for a 120W Offline BCM Flyback operating at 120VAC input. Its primary peak current is 4.97A. (as attached) This corresponds to a Bpk of 0.368T. (Switching frequency is approx 20kHz at the max load condition and this input volts)

We can see that Ferroxcube 3C92 material is much superior to the 3C90 material (though 3C90 comes with standard gaps)
The TDG TP4E material is said to be equivalent to 3C92 but actually has greater loss.

Can you confirm that the B value in these graphs refers to the peak B (not Bpkpk) with B as a sinusoid)?
Also, since we are using a flyback, then we can divide Bpk by two and then use that value with these graphs (since flyback does not have sinusoidal B , but rather, unipolar B)


Also, can you confirm roughly the cost difference between 3C90 and 3C92?

Ferroxcume 3C92 Ferrite:

https://ferroxcube.home.pl/appl/info/3C92&3C93.pdf

Ferroxcume 3C90 Ferrite:

https://elnamagnetics.com/wp-content/uploads/library/Ferroxcube-Materials/3C90_Material_Specification.pdf

TDG TP4E ferrite (page 38)

https://www.mhw-intl.com/assets/TDG/TDG 2006 MnZn Catalog.pdf

 

[FvM]

Also, since we are using a flyback, then we can divide Bpk by two and then use that value with these graphs (since flyback does not have sinusoidal B , but rather, unipolar B)

Surely not divide by two. You can use Ferroxcube SFDT 2010 tool to calculate losses for non sinusoidal B waveform.

 

[treez]

Thanks, but SFDT 2010 is only available for windows XP on the ferroxcube site
If you go to Frenetic website, you cant download it, but you can book an interview so they can decide how much you'll pay for it.
I then found a free download here...

Ferroxcube Ferrite Cores

ferroxcube.signal.com.tr

....but it wouldnt install...it gets stuck and crashes the computer every time you try.

Surely not divide by two.

I admit it wont be exactly divide by two.......but do you agree the core losses will be significantly less as a flyback is simply unipolar flux?

 

[FvM]

Maybe my fault that I simply ignored the "only Windows XP" comment given with the download at ferroxcube.com Unfortunately the software is just working for me under Windows 10. Otherwise I'd run it in a virtual box.

 

[Velkarn]

there is tool from Epcos - Magnetic Design Tool

 

[Easy peasy]

at full power, if the flux excursion is 0 - 325mT, then yes you can treat the delta-B as half of that each way ( ~ 162mT ) for the purposes of heating calcs due to flux & freq - this is not strictly accurate as, as you approach Bmax and the BH curve starts to roll over a bit - the losses here due to flux excursions are a wee bit higher than for the more linear portions of the BH curve, kind regards,

 

[treez]

Hi,
Soooo, we wish to use an E42/21/15 transformer for an offline BCM flyback at 30kHz f(sw)
We like 3C90 ferrite material but our peak B is 378mT, so we want to look at 3C95 ferrite instead. However, 3C95 graphs show nothing for core loss at 25kHz, whereas 3C90 graphs specify core loss at 25kHz. How does 3C95 core loss at 25kHz compare with that of 3C90 core loss at 25kHz?

3C90 ferrite:

https://elnamagnetics.com/wp-content/uploads/library/Ferroxcube-Materials/3C90_Material_Specification.pdf

3C95 ferrite:

https://elnamagnetics.com/wp-content/uploads/library/Ferroxcube-Materials/3C95_Material_Specification.pdf

 

[Easy peasy]

suggest far better to lower the Bpk

 

[FvM]

Here's the result with SFDT2010. The tool doesn't allow a flux above 360 mT for this material, because it considers it as saturation limit.

 

[Easy peasy]

3C95 -> 300mT abs max, else you are into Lmag falling rapidly scenario - esp at 100 deg C

3C90 -> 250mT abs max for same reasons ...