trafo-wiring....i need a ratio n=30

[Tobbe]

trafo-wiring....

i need a ratio n=30

to achieve optimum efficiency i've read that Pcore = Pwind.. and to achieve this ive used appropiate equations....but the result confuses me..... according to the calculations, Npri should be 31.....seems strange with one turn on secondary side...

if i go up to 60/2 the resistive losses will dominate and i will no longer reach Pcore=Pwind...

what to do?

 

[keith1200rs]

trafo-wiring....

Have you some more details? Power, core etc.

Keith.

 

[Tobbe]

Re: trafo-wiring....

2.5kW
freq= 100khz

ferrite 3c90
core= U93/76/30 (ferroxcube)

 

[keith1200rs]

trafo-wiring....

Currents/voltages?

Keith.

 

[Tobbe]

Re: trafo-wiring....

it is:
400/12 V
8/235 A

 

[FvM]

Re: trafo-wiring....

to achieve optimum efficiency i've read that Pcore = Pwind

In my opinion it's rather a rule of thumb for economic transformer design. You can always increase efficiency by using a
bigger core and more copper. The exact optimal design for each core size can be expected to achieve similar amounts of
core and copper losses, but they are not necessarily equal. As in your example, the result may be different because you
can only realize an integer number of turns.

 

[keith1200rs]

I tried some transformer tools and it came up with the same 1 turn answer for that core (and all other cores it suggested). I think that may be the best solution. I think that the problem is the core isn't physically big enough to fit more windings in. If you reduce the wire diameter to fit 2 turns in then you lose more in DC losses than the improvement in AC losses.

Keith.

 

[Tobbe]

but according to this equation:

N1 = (V1*Ts / Ae*Bpeak)

if i choose larger core and thereby larger effective area, N1 will decrease below 30.. if i then need n=30, it means that N2= 1/2 , 1/4 etc

 

[keith1200rs]

I don't think you can sensibly have less than 1 turn though, so you just have to accept that limit and choose the other winding accordingly.

Keith.

 

[Tobbe]

ive been looking at planar transformers...

tips on webpages for good understanding when it comes to the wiring....

i've understand that Planar transformers use the copper foil of multi-layer pcbs for the windings....

but how do i achieve this kind of winding on the secondary side..

https://www.elecfans.com/article/UploadPic/2009-4/200943014451638.gif

 

[karesz]

Hi,
You can try the (sec.)winding with a metall(practically copper) foil too.
If you will an simmetrical parametric double sec coil, take 2x metall strips in one layer...
K.

 

[Tobbe]

i dont understand...

 

[karesz]

Sorry,
whats here unclear pls: you wish to have a high current secondary coil>> make it from metall foil_you must take only a metall foil, isolate with high-temp. band & wind it turns over turns...
If you will 2x secondary coils with same length(parasitics) , wind both (similar as bifillar wires) next to each other... (it suggest the planar transformer for you too, but the coil is at 90 degre to bent/move to the core...)
K.

 

[FvM]

I don't see what planar transformers would change regarding your original question. They are restricted to integer number
of windings as well. I also don't think that you are able to implement a 2.5 kW transformer with planar technology.

Obviously, secondary and primary windings are build in the same way. But they have to share the available PCB layers. In my opinion, they
are mainly good for low or medium power and low windings count.

 

[Tobbe]

i dont see a problem with 2.5kW level .....or?

according to

https://www.himag.co.uk/docs/E64_Datasheet_-_Feb_2009.pdf

up to 9kW

 

[karesz]

Yea: all things are clear!
With so less imagination capability, but so much knowledge: it will be really not a problem!
Good progress!
K.

 

[FvM]

I agree, that's O.K. to call the himag devices planar transformers because of the 2D windings geometry. But they are not
the kind of planar transformers you mentioned in your post, because they are build from thick (0.5 to 1 mm) discrete
copper sheets instead of a multilayer PCB.

I wonder, if you understand the difference?

P.S.: The high power himag devices are quite interesting. But they probably have problems to implement a 30:1 windings ratio.