SMPS Transformer Design

[fethiyeli]

I would like to design a SMPS for inverter. Preferred topology is push pull but ı dont know whether it can handle this high power. I have a E65/32/27 core. Here are the list of the parameters.

Input voltage:30V
Input current:52.17A
Output voltage:311V
Output current:4A
Switching frequency:73kHz (not possible to use lower frequency with this core and this high power.)
Efficiency:80%

I have read this Transformer and Inductor Design Handbook - 3rd Edition and calculated all things ı need according to this book.

The maximum wire size diameter is 0.049cm due to the skin effect. It corresponds to 0.001884cm2 and #25 AWG cable.

Primary turns:1.93
Primary bare wire area:0.270cm2
# of primary strands:143 ( 143 x #25 AWG wire in order to get 0.270cm2 with least skin effect)

Secondary turns:20.1
Secondary bare wire area:0.0207cm2
# of secondary strands:11 ( 11 x #25 AWG wire in order to get 0.0207cm2 with least skin effect)

I need to wind this transformer myself. It is so hard or impossible to wind these 143 cables. How can ı wind this transformer with less cables ? ofc it can be possible but losses will increase with larger cables. So how can ı modify these number and size of cables in order to wind it myself ? Even if I wind it, ı need to remove the isolation of the 143 wires for soldering. You know its so hard ı think.

 

[chuckey]

If you measure the length of the path of the wire, say its X cm. Then add quite a bit , say 10cm. Then cut two bits of hardboard which is X+10 cms wide and say, 30 cms long. Tightly wind 72 turns of your #25 wire on it. Cut the wires top and bottom, along the joint of the two bits of hardboard, gathering the bits of wire as you go. Wrap bits of tape around your bundle to temporarily hold them. Give the bundle a twist and you are good to go.
Years ago I used a wire called "Bicelflux" (SP.?), this was insulated with an insulation that was burnt off by the soldering temperature. For a bundle of this size you must use a big soldering iron, at least an old fashioned 200 w iron with a big copper bit.
There is Litz wire available ( https://www.angelfire.com/electronic2/index1/Litz-Wire-Supplier.html ) in short lengths, but as you have not stated the csa of the conductor, I am not sure which one might be suitable. Proper Litz wire is very difficult to strip and tin, we used a methylated spirit lamp to burn off the insulation.
Frank

 

[goldsmith]

Hi fethiyeli
I think this thread consists many of the good information about what you're looking for . so take a look here please :
https://www.edaboard.com/threads/229615/

Best Wishes
Goldsmith

 

[fethiyeli]

Are all these practical methods for winding ? if yes, ı think it will be better for winding for amateurs =)

 

[goldsmith]

Are all these practical methods for winding ? if yes, ı think it will be better for winding for amateurs =)

Of course ! i guarantee if you read all of that thread precisely , then you'll be able to design many of the magnetic elements , easily ! i've used that way to cover many of the professional designs and all of them were successfully .
Best Luck
Goldsmith

 

[fethiyeli]

thank you so much goldsmith. ı will read them soon and design a transformer for SMPS.