Does winding multiple layers on trafo give high leakage inductance?

[grizedale]

Hello,

We are planning to wind a full-bridge transformer for isolated 90-265VAC use.

It has the secondary "sandwiched" between two layers of the primary.

Np = 114
Ns = 72


-First primary section = 3 layers of 19 turns

-Secondary section = 4 layers of 18 turns

-Second primary section = 3 layers of 19 turns


All layers are wound right across the whole bobbin window length.

-Due to the multiple layering, will this mean the transformer has higher than normal leakage inductance?

 

[mtwieg]

No, interleaved winding schemes like that are generally effective at reducing leakage. Beyond that there's not much you can do if your core doesn't have a gap, besides just using a higher permeability core (which doesn't really decrease leakage inductance, but will increase k a bit).

 

[atripathi]

It will have lower leakage inductance, and lower winding capacitance (you have broken primary into two and not only capacitance is reduced for each section, but these are connected in series to further reduce it.)
but you loose isolation between primary and secondary winding.

 

[grizedale]

thankyou mtwieg and Atripathi,

i appreciate that "sandwiching " of the secondary will reduce leakage.

...but what i mean is, the secondary itself is made of multiple layers...surely that will badly affect the transformer and make more leakage?

I mean, i could have used a bigger, more expensive core and just done a single secondary layer surrounded by 2 single primary layers.....would that have meant less leakage?

 

[rvionics]

Multiple Layers will have large leakage (Although you have sandwitched secondry in primary) as the N X I flux cancellation is poor in multiple layers
If you sandwitch your secondary at each layer you can reduce the leakage. for example 19T primary then 12T secandary then 19T Primary again 12T secondary & so on ( 19-12-19-12-19-12-12-19-12-19-12-19) this will give you the best results & very low leakage due to perfect N X I cancellation
this is very labour intense job but your leakage will be less.