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Is this inductor rated for the voltage it will see in this LLC converter?

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treez

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Hi,
We wish to use two MSS1278T 470uH inductors in series to achieve the L1 component (external magnetising inductor) in this LLC converter. Do you think the MSS1278T inductor is rated for this voltage? (each will see 150V peak maximum).

Datasheet does not tell of voltage rating.

Schem and LTspice of LLC attached

MSS1278T datasheet
https://www.coilcraft.com/pdfs/mss1278t.pdf



(Strangely, only the Wuerth WE-D HV range tell of the voltage rating)
 

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  • LLC 200W.jpg
    LLC 200W.jpg
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  • HB LLC 200W 60V.TXT
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Ask Coilcraft. According to specification of similar competitor products, I won't expect more than 120 or 120 V working voltage. -> not suited for 390 Vdc input.

Besides voltage rating, losses should be evaluated. Coilcraft loss calculator says 741 mW.

1593247768295.png

Würth has a similar series with dedicated HV inductors WE-PD HV. Best fitting 7687709102 gives even 1.5 W AC losses for the intended operation point. -> Too small form factor for the reactive power.

1593249782677.png

Why not integrating Lh with the transformer, using an air gap?
 

Why not integrating Lh with the transformer, using an air gap?
Click to expand...
Thanks yes, at this point we dont want to have to buy a gapped core, or get one gapped, due to unavailability & lead times respectively.
Its a PQ3535, and we find only the smaller cores are widely available offtheshelf in gapped form.
 

I see, but I fear you have to spend more room for an separate L1 component.

Most vendors are applying air gap in inner and outer legs for their prototypes. Grinding the air gap yourself is also possible.
 
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put a small air gap in across all three legs of the PQ => easy ... and keeps any gap length small
 
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