Offline flyback SMPS transformer has "gappy" shield windings 1

[waveboy]

Hi,
Just doing an Offline Flyback transformer for 13.7V and 3A output. VAC input is 240VAC.
We are doing it sandwiched [Pri1 – Bias - Shield1 – SEC – Shield2 -Pri2]
I found it impossible to wind the shield without “gaps” (as attached) between the coils, due to the uneven winding surface. (due to my club-handed winding) Do you think that it will still be OK? The shields are connected to Primary side (post rectifier bridge) GND.

You can see the blue tape between the coil turns due to the gaps
All coils are using Enamelled copper wire as we cant source TEX-ELZ (TIW) cheaply and at short lead time.

Shield winding as on page 8...

https://ac-dc.power.com/sites/default/files/product-docs/an18.pdf

 

[MacGyverS2000]

Shields are never perfect... but gaps can be filled in with some extra turns in the area of need. If this is for a prototype, I would just pay attention to any EMI you get from it... if it's low enough, move on with the real work.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[waveboy]

Thanks,
The thing is, as you know, the shield coil will have a voltage which alters polarity every switching cycle.
Shield1 also lies virtually alongside Primary1 (first half of primary coil). As such, we would like to have adjacent ends of shield1 and primary1 coils both positive and both negative at the same time. The thing is, if you receive a consignment of wound transformers from a winding company, then how, (without powering it up in a flyback), can you tell that they have correctly phased the shield windings?