Flyback transformer. No fiddley winding end returns?

[cupoftea]

Hi,

Going to do a 3W hi side supply Flyback transformer. For 2kW Half Bridge (100kHz) LLC off 400Vdc input.
As you know, No need for “standard” isolation constraints, so can you see any problem in winding the E16/8/5 as in the attached? (we don’t want to have to bring “fiddley” return wires back across the former for each winding since there seems no need)

 

[FvM]

Intrawinding insulation is achieved by the magnet wire even in the weakest class, but additional intrawinding insulation is required for 400V with superimposed 100 kHz AC. The picture doesn't show it.

 

[cupoftea]

Intrawinding insulation is achieved by the magnet wire even in the weakest class, but additional intrawinding insulation is required for 400V with superimposed 100 kHz AC. The picture doesn't show it.

Thanks, is that a regulatory thing or will it break over may i ask?

We will certainly use tape between layers....however some of the wire "ends" could still touch each other as they are going out from the former.

Thread 4 of this thread (below) shows a picture showing a Flyback switching node which goes 0 to 500V at 66khz, lying over a 0V enamelled wire.....it seems to be OK.....

https://www.edaboard.com/threads/litz-wire-ok-for-390v-4kw-100khz-llc-transformer.402137/

..but i get your point this is 100kHz. I am just wondering if we can "get away" with this?...as its only a cheap prototype.

 

[FvM]

Thread 4 of this thread (below) shows a picture showing a Flyback switching node which goes 0 to 500V at 66khz, lying over a 0V enamelled wire.....it seems to be OK.....

The application note shows foil insulation between winding start and end, except for point touch near the pin. When you wind primary and secondary above each other without intermediate foil insulation, the risk to hit a defect spot is increased by many orders of magnitude.

 

[cupoftea]

intermediate foil insulation

...Thanks very much...do you mean "tape"...eg polyimide tape?...ie tape between the layers.
Yes we will have a layer of polyimide tape between the layers.
But yes, as you imply, we wont be able to gaurantee having absolutely no touching points between the high dv/dt wire and other wires...