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# Core loss for ETD49 Full Bridge SMPS?

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#### cupoftea

Hi,
We are doing Full Bridge SMPS, Split coil sec, 380VDC to 175Vdc, 500W, 70kHz

One uses ETD49, N87 with 34:23 = Np/Ns, gap 0.1mm
Bpk = +/- 0.286T
Pri = 2 strands 7/0.22 TEX-ELZ (2 layers of 17 turns in series for 34 turns, sandwiching the 2 secs)
Sec = 2 strands 7/0.14 TEX-ELZ (1 layer of 23 turns for each sec)

Other One uses ETD54,N87 with with 36:24 = Np/Ns, gap 0.1mm
Bpk = +/- 0.186T
Pri = 2 pllel layers of 36 turns of 7/0.23 TEX-ELZ sandwiching the two secs
Sec = 1 layer of 2 strands of 7/0.15 TEX-ELZ for each sec.

Do you think +/-0.286T is too much for core loss?

hahaha - at 70kHz, +/- 0.3T - the core will heat the wdgs quite nicely - do you have a fan mounted on top of the transformer ? this should cure your ills - say at least a 3W fan
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BTW if you drop the Np from 34T to 36 T - all else being equal the peak B will drop by the same amount

in this case to 0.27 T

at 70kHz, +/- 0.3T - the core will heat the wdgs quite nicely -
Thanks, do you think it will be ok though, as we are using Litz wire, as in the top post?

as lot as you fit the fan you might get away with it ...

Hi,
Along similar lines.....
We now wish to do a 2kW Full Bridge LLC converter off 380Vdc at 100kHz.
We wish to use a PQ5050 core from TDK, with N87 material.

The B in the core is +/-0.137T (21 turn primary, Kapton gapped)

The below shows that this means a power loss in the core of 160kW/m^3. The core volume is 37230e-9 m^3. So that’s a core loss of 6W. Would you agree that this is too much?

N87 ferrtie material:

PQ5050 TDK core set:

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