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Transformer calculator (Public) / Re: TO DO list
« Last post by Silvio Klaic on December 29, 2017, 01:48:26 PM »
It is alive and I discussing here only about mains transformer design (50/60Hz), not particularly SMPS design.
Main reason is because I didn't work enough with SMPS to need such program to help me.
All programs which I create is to primarily help me in calculations and I publish most of them as free software to help others.

If somebody have knowledge and willing/time to help me I'm open to create calculator for any type of transformer design.
Transformer calculator (Public) / Re: TO DO list
« Last post by udhay_cit on December 20, 2017, 10:25:22 AM »
Hi, Sorry I'm a late comer for this forum. Even though this forum has minimal discussion page, it is very informative. I don't see any recent activities in this page and don't know this is still alive or not, but I have no idea about what program you are discussing about regarding the SMPS design.
I'm trying to design my very first flyback SMPS design and gathering information related to that. If any such software available to simplify my job, please share with me. For learning, all the design  I have to study and understand by myself, but if I can finish my design with a help of some softwares for the first time only, it will be a motivation for me to move further.

Thank you for your information that took me to read. It was very helpful to me.
Other (Public) / Re: Pulse charger...
« Last post by Coplan on November 11, 2017, 01:56:24 PM »
Anyway this is idea, after testing and building prototype I’ll post results.
WARNING: Do not attempt to do this at home, this uses live AC current and it can easily kill you!
Remember, I’m trained amateur and I know what I’m doing. ;)

Sounds like a challenge to me.  :) Seriously though, thanks for the infol. I'd love to make my own pulse charger.
I have a lot of unknown ferrite cores mostly salvaged from radio/TV and other devices.
Main problem with this is to how to win bets with zcode know their permeability for calculating number of turns I need to make choke or transformer.

This is extremely helpful, thanks Silvio.
Transformer calculator (Public) / Re: Links to calculation pages
« Last post by Silvio Klaic on September 23, 2013, 01:21:21 PM »
Yes, given formula is for steel laminated cores at frequency of 50-60Hz.
If you change frequency or core material, that formula no longer apply.

The best solution is to find detailed specification of core material from manufacturer.
You can also test core to see how it behaves, but that is far more expensive.
Transformer calculator (Public) / Re: Links to calculation pages
« Last post by mbe200 on September 23, 2013, 09:26:07 AM »
Hi Silvio
You did it again. I think congratulations are in order. Than you for the power formula and the zip file. Now the calculator work fine. Is it correct to think that the power formula CSA squared is for normal steel laminations. If it is so what happens when one uses an Amcc core. I am experimentind with an Acc core 320  CSA is 22mm x 50mm (11cm square)
Thank for everything and nice to chat with you.
Best regards
Transformer calculator (Public) / Re: Links to calculation pages
« Last post by Silvio Klaic on September 22, 2013, 08:06:33 PM »
Formula for power of core is cross-sectional area squared: P=S2
Where P is power in watts for 50/60 Hz, S is cross-sectional area in cm2

Because many have problem with installation of my calculator on 64bit, here is archived installed version:
Download it and unpack to C:\Program Files
You may run it on compatibility mode for Win XP.

Hope it helps.
Transformer calculator (Public) / Re: Links to calculation pages
« Last post by mbe200 on September 16, 2013, 01:03:36 PM »
Hi Silvio
Nice work on your website.
You did a lot of work.
I tried to download the program but unfortunately it does not work on my lap top due it is 64 bit
It is possible to give me at least the workings to calculate at least the power from core cross-sectional area.
I  thank you for your time and for sharing
best regards
mbe 200
I have a lot of unknown ferrite cores mostly salvaged from radio/TV and other devices.
Main problem with this is to how to know their permeability for calculating number of turns I need to make choke or transformer.

So I needed some simple method to test cores and get theirs permeability.
Simplest way to me is to measure inductivity of choke with unknown core when you know how many turns of wire you have on it.
Then calculate from this inductance factor AL and effective permeability μe of core.

Usually you can find formulas for calculating in manufacturer Data Handbook or production guide.
The AL factor is the inductance per turn squared (in nH) for a given core.
Inductance formula is: L = N2*AL (nH)
When transformed, you can calculate AL with next formula: AL=L/N2
Once you have core data, value of AL is calculated from the core factor Σ(l ⁄A) and the effective permeability: AL= (μ0e*106)/ Σ(l ⁄A) (nH)

To get effective permeability, formula is transformed into this: μe = (AL*Σ(l ⁄A))/(μ0*106)
AL is calculated from measured inductance and number of turns.
Σ(l ⁄A) is calculated by measuring and dividing core physical dimensions of effective length le (mm) and effective area Ae (mm2): Σ(l ⁄A) = le/Ae (mm-1)
μ0 is permeability of vacuum - μ0 = 4*π*10-7 (Hm-1)

This formulae works for most core types except for rods and tubes, for them you need this formula: L = (μ0rod*N2*A)/l (in H)
After transforming we get: μrod = (L*l)/(μ0*N2*A)
L is measured inductance
N is number of turns
A is cross sectional area of rod (mm2)
l is length of coil. (mm)

With this solved only thing to do is to determine optimal number of turns for measurement.
By using large number of turns there is problem with rise of loses by wire resistance, coil geometry and core loses.
Therefore best is to use fewer as possible.
With minimal number of turns, wire length is reduced, thus wire resistance is low.
Beside that with few turns we don't have overlapping wire and loses in coil construction.
However when using single or few turns there is problem with covering entire space on coil former to get fully distributed winding to use entire length of core.

So to solve that problem I did some testing. For my test I chose RM6S/I ferrite core.
I was using three different core materials 3H3, 3C90 and 3E5 and I make coils with different number of turns, form 1 to 31.
For measuring inductance I was using Agilent U1731C LCR meter (resolution 1-100nH, accuracy 1%) with 100 Hz and 1 kHz setup.

Wire thickness is another important part, if it is too thick you can get losses from skin effect.
On another hand if you use too thin wire you can get losses in wire resistance.
For my setup maximal measuring frequency is 1 kHz and on that frequency skin depth is 2.088 mm, thus wire must not be larger than AWG 6.
I choose to use SWG 25 (diameter 0.5 mm) with max frequency of about 80 kHz. Using this wire I can fit 9 turns on former in single row.

One set of measuring was done from 1 to 31 turns with all cores exchanged on that turn. I repeat that set three times.
At end after several hundreds core swapping I compare readings from beginning and end.
Difference in data is from -4.62% to 43.37% which is primary result of loosening mounting clip after so many reassembling.
Most difference (higher than 10%) I got after 22nd turn which just confirms that less turns are far better for precision even in loose clip mounting.

Comparing 100 Hz vs. 1 kHz measurement data gave me difference from -7.51% to 0.98% which is not that bad.
Data from 1 kHz are much more close to datasheet values so it confirms that higher frequencies are better for measuring lower inductivity.

All processed data are from measurement at 1 kHz setup. Those values are used to calculate AL and compared with value from datasheet.

Here on this graph you can see difference for each core material.
For 3H3 material stable results is between 5th and 20th turn, for 3C90 is from 3rd and 31st turn and for 3E5 it looks there aren't stable results however after 21st turn difference are gone totally wild.
So it is safe to say that measuring from 5 to 20 turns gives best results.
To get and calculate permeability the best method is:
  • if possible, use high measuring frequency but close to working frequency of core
  • use 5 to 20 turns (closer to 5 turns for high amplification cores)
  • use thickest wire possible depend on measuring frequency and space on former
  • fill up equally entire length of former in single row
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