[SOLVED] Litz wire and others questions

[jmx66]

Hi all,

I plan to build one transformer with ETD49 core from Epcos, for a SMPS power supply.
Output: 10 40 V and 20 A continuous, not peak.
Frequency: 50 kHz

Main concern is about litz wire,and how much current allowed.

Power transformer 1:1, after rectifying from transformer RKT80030, chopping and gate driving, then rectifying again.

http://www.reichelt.de/Transformers...=2;ARTICLE=40448;GROUPID=3321;artnr=RKT+80030

1 or 2 layers and 200 x AWG 44:

**broken link removed**

Is it right choice?

Read and googled a lot, and some guys said that under 80 kHz, skin effect has little effect. Right or wrong?

About mean turn length: only mean diameter x 3,1416 ?

If i have 2 or 3 layers : say 3 layers : ( mean diameter of layer 1 + mean diameter of layer 2 + idem for layer 3 )/ 3 ?

It's very basic questions, but i'd like to know results.


Thanks a lot.

jm

 

[FvM]

A 20 A winding must have sufficient wire cross section, ending up in may be 1.5 or 2 mm diameter. Considering 0.3 mm skin depth at 50 kHz, and proximity effect in addition, a massive wire won't be very effective. Stranding multiple enamelled wires of e.g. 0.5 mm diameter would be a good compromise.

I don't understand some points of your post. I would suggest the Epcos Ferrite tool for transformer calculation.

 

[jmx66]

Hi fvM,

First, thanks a lot, as usual your reply is really concise.

In fact, I'm trying to modify this schematic, for a safiest power supply: Range 10 30-40 V 20A continuous not peak value.

https://uzzors2k.4hv.org/index.php?page=benchsmps1

So I plan to add RKT 80030 between mains and filter, in the first rectifying stage.

https://www.reichelt.de/Transformer...46;ARTICLE=40448;GROUPID=3321;artnr=RKT+80030

Replace in first bridge 4 x 400 V 8A by:

https://www.reichelt.de/Rectifiers/...LA=2;ARTICLE=4608;GROUPID=2998;artnr=B125C35A




IRFP450 by a more potent item:

https://www.reichelt.de/Transistors...=2;ARTICLE=41701;GROUPID=2893;artnr=IRFP+260N


My initial post was about the power transformer - initial schematic 1:2.4.

As i added RKT80030, i choose a ratio of 1:1.


Than half wave rectifying last stage - initial schematic 2x 30 CPU04 - replaced by full wave unit.

In this case, where to connect '' Power Ground '' above 0,01 Ohm 5 Watt?


Now i'm going to search for right filter after mains: for EMI or RFI i think.


For skin effect you use: 66 / Sqrt( F) ? F: Hertz

When a stranded cable is say, 5 x 100, it means 100 strands and one is 5 mil in cooper diameter,without insulation, so 25,4 x 0,001 x 5 = 0,127 mm diameter ?


Thanks a lot for your reply.

PS: As this post is a long one, i'm going to draw a schematic to clarify what i really plan to build.


jm

 

[jmx66]

Hi all,

I draw a schematic. -

Two questions:

- where to connect '' Ground power '' above 0,01 Ohm and 9W ?

- for voltage range of 10 to 30-40 V, do i change values or resistors:27 k, 100 k and 6,8 k Ohm to get it?
In short, it's mainly, before using it for general purpose high power supply, to test devices under 12 and 24V, up to 20 A continuous, not peak.

Linear power supplies have really baaaaad efficiency.:-(


Among modifications is full-wave rectifying after main power transformer:

- 4 x MBR2020CT good choice ?

https://www.reichelt.de/index.html?ACTION=3;ARTICLE=41967;SEARCH=MBR

View attachment A100_MBR20200CT_ONS.pdf


15 V is provided by an auxiliary card to build: not afraid about it, already built some and works perfectly.

Idem for 5v power supply.


Thanks to all, and have a nice day.

jm

 

[FvM]

I don't see a purpose of the 50 Hz transformer, I don't understand the voltage levels. The schematic suggests a HV DC bus but the transformer is 230/30V.

 

[jmx66]

Hi FvM,

Initial schematic '' played '' with 220 x 1,444 so 320 AC, then rectified so about 300 V DC.
Then divide 300 / 2 still 150 V DC.
I only want to use lower voltage, to increase safety;my only need is 10 30 40 V and only 20A: use of 230/30 50Hz transformer RKT80030.
I thought it was like '' an isolation transformer '' , not the same of course.

Surely make some mistakes in this schematic but how to get desired voltage,on power transformer?


Thanks a lot.


jm

 

[jmx66]

Hi all,

I've just found this chart on a web site.

View attachment Round_Litz_Catalog.pdf

Hope this helps.

jm

 

[HongSuk Kim]

Hello.

In case of 50khz, 36 or 38 AWG is suitable.
May we know how much quantity do you need per batch ?

We are Korean manufacturer of HF Litz Wire.

Please get more information from our website, www.hflitzwire.com
and email us, info@hflitzwire.com & info@ydkgroup.com

Warm Regards,

HS Kim(Mr.), Marketing Manager