SMPS Transformer Primary Turns Calculations

[ravs]

hi microsim,

i think you have seen it on ********.yes iam building lukas smps.there also iam looking for help.to confirm that iam going in the right direction
so that my first smps project desent get fail.that calculation is fully based on marty browns
280 watt half bridge example in power supply cookbook and also from practical switching
power supply design example.iam reading these books for around 5-6 months. spending
almost 6-7 hours a day .searching on the net for information.my hard disk space is almost full of
application notes and various smps,audio amplifier schematics.i didnt find the formula
on the net.as i already said iam following marty browns book theres a lot of mistakes in the printing.
the formulas are also messed up even the design examples have errors.i dont have any problem
sharing that stuff here if you allow me.i have seen you have deleted ******** from many posts in this forum.i knew the issues going
on.

i have done a step by step transformer desin procedure.first i stuck on primary turns calcuation
coz it was half bridge my turns were far way off from the originals.again started reading different books
then i found in half bridge input voltae is divided by 2.then again right iam stuck on secondary turns
calculation.iam not sure the formula iam using is right or not.ill post all that stuff here.i have seen
knowledgable people not replying to those who know very little.i keep posting the the stuff i find usefull
over here.how can i comment on the stuff i dont know about.iam trying to gain as muvh as possible from
you people.there are some people willing to help including you.

thanks a lot for all your help.ill post the whole calculation over here
including the schematics and pcb.



best regards

ravs

be a vegeterian

 

[MicrosiM]

hi microsim,

i think you have seen it on ********.yes iam building lukas smps.there also iam looking for help.to confirm that iam going in the right direction
so that my first smps project desent get fail.that calculation is fully based on marty browns
280 watt half bridge example in power supply cookbook and also from practical switching
power supply design example.iam reading these books for around 5-6 months. spending
almost 6-7 hours a day .searching on the net for information.my hard disk space is almost full of
application notes and various smps,audio amplifier schematics.i didnt find the formula
on the net.as i already said iam following marty browns book theres a lot of mistakes in the printing.
the formulas are also messed up even the design examples have errors.i dont have any problem
sharing that stuff here if you allow me.i have seen you have deleted ******** from many posts in this forum.i knew the issues going
on.

i have done a step by step transformer desin procedure.first i stuck on primary turns calcuation
coz it was half bridge my turns were far way off from the originals.again started reading different books
then i found in half bridge input voltae is divided by 2.then again right iam stuck on secondary turns
calculation.iam not sure the formula iam using is right or not.ill post all that stuff here.i have seen
knowledgable people not replying to those who know very little.i keep posting the the stuff i find usefull
over here.how can i comment on the stuff i dont know about.iam trying to gain as muvh as possible from
you people.there are some people willing to help including you.

thanks a lot for all your help.ill post the whole calculation over here
including the schematics and pcb.



best regards

ravs

be a vegeterian

ravs.


I would like to help you, and you already know that.

I gave you formula, and you still confused.

Download it friend, ask here, post screen shots.

I will help you make it.

Best wishes

 

[ravs]

hi microsim,

thanks for your support.i myself confused reading so many books every book has different calculations.

here is the whole step by step calculation i have posted there

half bridge transformer calcultion for 500 watts power .50-0-50 5amp

vin min=180 volts

vin max=270 volts

efficiency=80%

output power=50x5+50x5

=250+250=500watts

estimated input power

pin est=output power/efficiency

=500x80/100

=625 watts

dc input rms voltages

vin low=1.414x180=254 volts

vin high=1.414x270=382 volts

average input current

highest average current=po/vin min

=500/254=1.96 amp

lowest average current=po/vin max

=500/382=1.30 amp

estimaed peak input current

Ipk=2.8xpo/vin low

=2.8x500/254=5.51 ampere

estimating no of primary turns

npri={(vin min/2)x10^8}/4xfxbxac (4=square wave, f=50khz, b=2100 guass, ac=2.11 cm^2 for etd49)

=(254/2)x10^8}/4x50x2100x2.11

=14.33 turns or 15 turns

n sec={1.1(vout+vfd)xnpri}/vin min x dmax { vfd=diode voltage drop dmax=duty cycle=0.95}

nse={1.1(50+1)xnpri}/127x0.95

=6.97 turns or 7 turns

calculating skin effect

sd=6.62/sqrt f cm

=6.62/sqrt 50000 = 0.0296

wire diameter=2xsd=2x0.096

d=0.0592 cm

bare wire area =3.14x(d*2)/4 =3.14x(0.0592^2)/4

=0.0027s cm2

nearest bare wire area is of 23 awg thi is the lowest wire guage that will be used to avoid skin effect
but i will be using swg wires.

awg 23=0.0028 and swg23=0.00298 cm^2

calculate bare primary wire area

Apw=(Iin high x sqrt dmax)/j i=current density 500cirmills/amp dmax=duty cycle

=1.96xsqrt 0.95/500

=0.00382

no of stands required for primary=Awp/0.00298 {swg23 area}

=0.00382/0.00298=1.28 or 2 strands of 23 swg

now
calculate baresec wire area

Asw=(Io x sqrt dmax)/500

=5 x sqrt 0.95/500

=0.0097cm^2

no of strands fo sec =swp/0.00298

= 0.0097/0.00298 =3.25 or 4 strands of 23 swg

ill be using etd49 of cf139 material
http://www.cosmoferrites.com/material_info.html

is all these ok .calculation of no of strands and skin depth is used from transformer and inductor design handbook by colonel wm t mclyman.should i proceed building transfrmer.please look at secondary turns calculation


thanks in advance

ravs


be a vegeterian.....

 

[MicrosiM]

Complex

ravs


In my opinion, You are complicating things for no reason.

If you are using ETD44 as indicated @70Khz @ 1200 Bmax

Primary turns is 26 Turns

for 50 - 0 - 50 VDC output you need 8 turns -0 - 8 turns

at least you need 1.2MM for Primary if you need 600W, strand many thin wires together, its known method, See ludo3232 how he did it.

Other wise I cant see any thing prvents that SMPS from working.

* where did you get the Vin Max 270v from?


Help is there always

Thanks

 

[ravs]

hi microsim,

iam using etd49.after this completes successfully ill increase the output to 80-0-80 volts 1kw thats why iam using etd49 at 50khz,2100guass.

now microsim 1.2mm wire decided considering primary current of 1.96 amp right.then what about the primary peak current of 5.51 ampere.now suppose i use 23 swg wire so how many strands of it.

1.2mm = 18 swg=2303.93 cir mills
0.06096= 23 swg=575.983 cir mills

no of strands required=2303.93/575.983
=3.99 or 4 strands

or should i go with single wire of 18 swg.

in winter season the line voltage goes 270-280 volts

best wishes

ravs

be a vegeterian....

 

[MicrosiM]

hi microsim,

iam using etd49.after this completes successfully ill increase the output to 80-0-80 volts 1kw thats why iam using etd49 at 50khz,2100guass.

now microsim 1.2mm wire decided considering primary current of 1.96 amp right.then what about the primary peak current of 5.51 ampere.now suppose i use 23 swg wire so how many strands of it.

1.2mm = 18 swg=2303.93 cir mills
0.06096= 23 swg=575.983 cir mills

no of strands required=2303.93/575.983
=3.99 or 4 strands

or should i go with single wire of 18 swg.

in winter season the line voltage goes 270-280 volts

best wishes

ravs

be a vegeterian....

If you know the diameter of the wire you need, *You Must* use strands, as much as you can, until u reach the required diameter.

Example:-

1mm required, i can use 5 srands x 0.2mm or 0.1mm x 10 strands

hope its clear

 

[MicrosiM]

New

My Friend MicroSim,
As I had already reviewed it, I'm developing the power switch quasi resonant, but now I have two serious problems:
Its formula can be used with Quasi Resonant power supplies? if so how should I proceed to calculate the inductor and capacitor are in series with the transformer?
I need urgent help from you guys,
awaiting,
a hug to everyone,
Cleber

Any updates about your SMPS?

 

[MicrosiM]

Updates

Updated version of formula for secondary turns calculations!

 

[kubeek]

Doesn´t 9700 turns seem to be a bit too much for a primary winding at 70khz?

 

[MicrosiM]

turns

Doesn´t 9700 turns seem to be a bit too much for a primary winding at 70khz?

hmmm



I think you are missing something

lets see what you have entered there, and find out how you came up with that number of turns.

Please show

 

[IGBT]

seperator

WTF?

9700 turns?

Dont read the 9,700 is 9700 turns ((@

It means 9.7 turns, almost 10 Turns


Formula for half bridge ONLY.


I am sure that you are doing something wrong.

Tel us witch core you are referring to, freq, and all of that informations to help you out

 

[kubeek]

When you open that table there already are numbers filled in and it says 9705 turns. I even tried to copy and paste that cell to see it really is 9705 turns. Here is the screenshot

 

[MicrosiM]

When you open that table there already are numbers filled in and it says 9705 turns. I even tried to copy and paste that cell to see it really is 9705 turns. Here is the screenshot

That is 9.7 Turns

witch is close to 10

 

[MicrosiM]

Check attached


I can see the separator in my Excel

Make sure you see it


thanks for pointing that out, i will look if others have same issue

 

[kubeek]

But that is a thousands separator, Ae is correctly 1 point 25, but the result is 22 comma 794 when it should be 22 point 794, so it is three zeroes off. Probably the frequency should be in Hz and not kHz.

 

[MicrosiM]

Formula

But that is a thousands separator, Ae is correctly 1 point 25, but the result is 22 comma 794 when it should be 22 point 794, so it is three zeroes off. Probably the frequency should be in Hz and not kHz.

Its clearly indicated that frequency in KHZ, as above of the frequency field, see it

Things are clear

you are the first who faced problems, witch version of MS EXCEL you have?

 

[kubeek]

Yes it is indicated in KHz, but it should be in Hz to produce the right number. Try copying that number and paste it some where else like notepad, it is 22794.
Once again, there is a different decimal point in the Ae than in the number of turns, 1.25 vs 22,794.

 

[kubeek]

Anyway, the voltage you enter is the rectified mains voltage, or half of it?

 

[MicrosiM]

Voltage

Anyway, the voltage you enter is the rectified mains voltage, or half of it?

That formula for HALF BRIDGE

160V is HALF the rectified voltage witch is 340VDC, because the transformer will see HALF of it.

If you check schematics carefully, you will notice that.

Usually I calculate for LOWEST voltage expected at the primary side, thats why I go for 150V ~ 140V

Some designers calculates for WCD worst case design witch is 90V


Thanks

 

[MicrosiM]

@ KubKeek

If you are making SMPS, i will be glad to help you out making one