Litz wire for use in Boost PFC inductor winding?....informative datasheets available?

[zenerbjt]

Hi,
Does Anybody know of any off-the-shelf vendors of Litz wire for winding of Boost PFC inductors? (We need Litz as the coil will be near a gap in the ferrite and exposed to the fringing field)

We know of Furukawa TEX-ELZ, but we don’t need the triple insulation, and would like more strands than the seven that TEX-ELZ gives….

TEX-ELW TIW Litz:
https://www.furukawa.co.jp/tex-e/en/product/texelz.html

Other than Furukawa, none of the Litz wire vendors offer a Litz wire datasheet with sufficient info on it for you to decide if the wires were suitable or not (eg, they don’t give the insulation rating, don’t say if its solderable, don’t give the overall max outer diameter, etc etc).

Power integrations recommend “served Litz Wire” (anything from 40 to 60 strands of AWG38) in all of their PFC Application notes eg DER-484. I contacted Power integrations for the part number, and they just gave me two company names, “mwswire.com” and “newenglandwire.com”. However, I contacted mwswire.com, and they just emailed me back and told me to ask Power integrations which Litz wire part number they were referring to.

Does anybody know of any Litz datasheets for offtheshelf Litz wire that we can look at?

We need an insulation test rating of 500VAC for 1 minute at <500uA.

 

[Easy peasy]

google it - there are plenty - also EBAY for small quantities ...

--- Updated Dec 27, 2020 ---

work out the mm^2 you need, choose a wire size for the litz based on freq etc, e.g. 38 AWG, then divide to get the No. of strands, then choose a litz near to this ....

 

[zenerbjt]

Thanks, as you know, googling reveals millions of Litz vendors, but nobody has anything offtheshelf for gerneral inductor winding with a datasheet which indicates insulation rating, overall max diameter, and whether the coating is "solderable through".
We've emailed a few vendors and asked for eg 60*AWG#38.
For the insulation rating, we asked for "500VAC for 1 minute and 1mA"
Is that the right way to specify wire insulation for a PFC inductor on 240VAC?

I am guessing that we are going to have to have this Litz custom made?

 

[Easy peasy]

good searching skills are essential for the modern engineer - there are such things as filtering and narrowing search criteria

for example:

10m ( 33ft) litz wire 300/38, 0.1mm x 300 strands | eBay

Find many great new & used options and get the best deals for 10m ( 33ft) litz wire 300/38, 0.1mm x 300 strands at the best online prices at eBay! Free shipping for many products!

www.ebay.com

custom litz starts at GBP 5000 and goes up from there ....

--- Updated Dec 30, 2020 ---

Litz wire 170/40 for High-frequency Equiment coil, Single layer insulation, 100' | eBay

When you pull out the litz wire from the paper spool, the paper spool can rotate freely on the screw rod, and the litz wire will not be twisted and knotted. We have hundreds of sizes of Litz wire for sale.

www.ebay.com

 

[zenerbjt]

Thanks, those are the best we've seen yet.
They say they are "nylon coated", but we still feel a little nervy putting that in offline transformers and inductors.
We'd like to see some statement about insulation rating in a datasheet.
We could of course buy it in and test it with our insulation tester...but then we couldnt be sure the next batch would be the same.
One says its made up of "individually insulated enameled copper wires", but we'd like to see a formal insulation rating statement.
(Sorry, but We fear that some middle man might have bought up some cheap Chinese stocks and be re-selling them on ebay?)

Ive just had a company come back to me for a quote for custom build of Litz, where we can specify, but there is a 305 metre MOQ.

In fact, what we are looking for is a datasheet like the following, but for multi strand Litz wire....

https://www.farnell.com/datasheets/3170015.pdf

...this gives maximum outer diameter, insulation rating, temperature rating, whether its square or circular xsection, even maximum DC resistance.

We cant find any Multi strand Litz with this kind of datasheet.

 

[FvM]

Nice datasheet, 7 kV breakdown voltage is just unrealistic for class 2 polyurethane insulation.

Most litz wires available on the market have solderable (155 °C rating) PU insulation, some have additional coating or textil/foil wrapping.

I have no idea how you want to perform a 500 VAC/1min test with an inductor, except possibly for winding to core. I expect that regular enamelled magnet wire and also unserved litz wire would pass the test. But it's no appropriate test voltage for 240 VAC 50 Hz and not at all for high frequent voltage. If you don't want to rely on special litz wire qualities, why not apply standard layer insulation for the inductor?

 

[Easy peasy]

teflon coated litz is avail - even up to 3 layers of teflon coating -

RUPALIT® high-frequency litz wires

RUPALIT® high-frequency litz wires are constructed from RUPOL®, RUPEX® or RUTHERM® enamelled copper wires. (aluminium wires on request)

www.packlitzwire.com