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How to Design Your Own Inverter Transformer

Designing an inverter transformer can be a complex affair. However, using the various formulas and by taking the help of one practical example shown here, the operations involved finally become very easy.

The present article explains through a practical example the process of applying the various formulas for making an inverter transformer.The various formulas required for designing a transformer has been already discussed in one my previous articles.

Update: A detailed explanation can be also studied in this article: How to Make Transformers

Designing an Inverter Transformer

An inverter is your personal power house, able to transform any high current DC source into readily usable AC power, quite similar to the power received from your house outlets.

Although inverters are extensively available in the market today, but designing your own customized inverter unit can make you overwhelmingly satisfied and moreover it's great fun.

At Bright Hub I have already published many inverter circuit diagram, ranging from simple to sophisticated sine wave and modified sine wave designs.

However folks keep on asking me regarding formulas that can be easily used for designing a inverter transformer.

The popular demand inspired me to publish one such article dealing comprehensively with transformer design calculations. Although the explanation and the content was up to the mark, quite disappointingly many of you just failed to grasp the procedure.

This prompted me to write this article which includes one example thoroughly illustrating how to use and apply the various steps and formulas while designing your own transformer.

Let’s quickly study the following attached example:Suppose you want to design an inverter transformer for a 120 VA inverter using a 12 Volt automobile battery as the input and need 230 Volts as the output. Now, simply dividing 120 by 12 gives 10 Amps, this becomes the required secondary current.

Want to learn how to design basic inverter circuits?

In the following explanation the Primary Side is referred to as the Transformer side which may be connected at the DC Battery side, while the Secondary side signifies the Output AC 220V side.

The data in hand are:

Secondary Voltage = 230 Volts,

Primary Current (Output Current) = 10 Amps.

Primary Voltage (Output Voltage) = 12-0-12 volts, that is equal to 24 volts.

Output Frequency = 50 Hz

First we need to find the core area CA = 1.152 ×√ 24 × 10 = 18 sq.cm where 1.152 is a constant.

We select CRGO as the core material.

Calculating Turns per Volt TPV = 1 / (4.44 × 10–4 ×18 × 1.3 × 50) = 1.96, except 18 and 50 all are constants.

Calculating Secondary Current = 24 × 10 / 230 × 0.9 (assumed efficiency) = 1.15 Amps,

By matching the above current in Table A we get the approximate Secondary copper wire thickness = 21 SWG.

Therefore the Number of Turns for the Secondary winding is calculated as = 1.96 × 230 = 450

Next, Secondary Winding Area becomes = 450 / 137 (from Table A) = 3.27 sq.cm.

Now, the required Primary current is 10 Amps, therefore from Table A we match an equivalent thickness of copper wire = 12 SWG.

Calculating Primary Number of Turns = 1.04 (1.96 × 24) = 49.

Calculating Primary Winding Area = 49 / 12.8 (From Table A) = 3.8 Sq.cm.

Therefore, the Total Winding Area Comes to = (3.27 + 3.8) × 1.3 (insulation area added 30%) = 9 sq.cm.

Calculating Gross Area we get = 18 / 0.9 = 20 sq.cm.

Next, the Tongue Width becomes = √20 = 4.47 cm.

Consulting Table B yet again through the above value we finalize the core type to be 6 (E/I) approximately.

Finally the Stack is calculated as = 20 / 4.47 = 4.47 cm

Table A

SWG------- (AMP)------- Turns per Sq.cm.
10----------- 16.6---------- 8.7
11----------- 13.638------- 10.4
12----------- 10.961------- 12.8
13----------- 8.579--------- 16.1
14----------- 6.487--------- 21.5
15----------- 5.254--------- 26.8
16----------- 4.151--------- 35.2
17----------- 3.178--------- 45.4
18----------- 2.335--------- 60.8
19----------- 1.622--------- 87.4
20----------- 1.313--------- 106
21----------- 1.0377-------- 137
22----------- 0.7945-------- 176
23----------- 0.5838--------- 42
24----------- 0.4906--------- 286
25----------- 0.4054--------- 341
26----------- 0.3284--------- 415
27----------- 0.2726--------- 504
28----------- 0.2219--------- 609
29----------- 0.1874--------- 711
30----------- 0.1558--------- 881
31----------- 0.1364--------- 997
32----------- 0.1182--------- 1137
33----------- 0.1013--------- 1308
34----------- 0.0858--------- 1608
35----------- 0.0715--------- 1902
36----------- 0.0586---------- 2286
37----------- 0.0469---------- 2800
38----------- 0.0365---------- 3507
39----------- 0.0274---------- 4838
40----------- 0.0233---------- 5595
41----------- 0.0197---------- 6543
42----------- 0.0162---------- 7755
43----------- 0.0131---------- 9337
44----------- 0.0104--------- 11457
45----------- 0.0079--------- 14392
46----------- 0.0059--------- 20223
47----------- 0.0041--------- 27546
48----------- 0.0026--------- 39706
49----------- 0.0015--------- 62134
50----------- 0.0010--------- 81242

Table B

4AX(U/T) ----------------2.383-----------13.039


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

203 thoughts on “How to Design Your Own Inverter Transformer”

    • Thank you John, If the recommended transformer is an iron core transformer then yes it can be implemented for the mentioned circuit…

  1. Hi swagatam,my name is ibrahim from Nigeria i would like to thank you for the detailed explanation of transformer design,may God reward you.sir ive gone through the calculations which are very clear to me my only problem is i want to design a 1kv inverter transformer i dont have problem with the calculations but the table. Can you please help me with a table chart that can handle upto 100amp? thanks and God bless

  2. hello sir, I hope you are doing well and how is your work? sir, I thank you for the automatic cut off voltage regulator circuit which you send it to me in a couple of some days back. sir, this time I I need your advice. I am a Nigerian, from TARABA state.sir,between electronics and power or electrical, which one is more better to study so that one can be easily self reliance and he shall be accepted quickly when looking for a government work. the reason behind my question is that, I’m a student from mautech Yola university, and we just resume to run the first semester 300level.so,we are ask by the University to choose one in between the two to follow. although, I read electronics during my technical secondary school.

    • Hello Emmanuel, Electronics is better because it has a wider scope and the future world will be heavily dependent on this subject. However electronics can be a lot more difficult than electrical, so choose wisely.

  3. hi sir, I can stop thanking you. please sir, can I get one of inverter circuit and a cut off voltage circuit I.e,when the battery full, will stop it from charging and when it’s run down a little, like 10 percent out it will get it back to charging. please sir, that is my email. (emmygangba@gmail.com).

  4. hello sir, I’m still thinking you. sir you said my battery voltage is lower than the transformer ratting, please sir can I have explanation of how your know the transformer rating.

  5. hello sir, thank you for the reply! the load I used was one bulb and my phone charger,thou it is charging the phone well, but when I connect the supply wire to the battery, the supply wire started getting hot as well with the two mosfet. so, the battery ratting is 62Ah.i have tested the transformer according to step down, just as you said, the voltage spec I got was 15v

    • Hello Emmanuel, in your case the battery voltage is lower than the trafo rating so there shouldn’t be any heating due to transformer primary. You can check by disconnecting the drain of the mosfet from the transformer taps, if the mosfet don’t heat then the problem could be somewhere in the transformer.

  6. hello sir,good evening.my name is John,i constricted inverter using 12v battery and then I used a transformer from my old transformer, Thau, I don’t know the wattage of the transformer but it still works. so, my question is that, the two irf150 mosfet from my circuit are getting hort.pleace sir what is the problem?

    • Hello Emmanuel, what is the load that you have used? If the transformer voltage rating is too low compared to the battery then the mosfet will become unnecessarily hot.

      Disconnect the transformer, and from the 220V side feed AC 220V and measure the AC on the secondary side to now the exact voltage spec on the step down side of the trafo…

  7. Hi Swag,
    I was trying every of your inverter circuits for experiment. but always most difficult part for me is find a current Transformer. and today I found two units of old Microwave oven transformers. and I have carefully remove the high voltage part. now I want to rewind both transformers one for 1000W inverter, other one for 500W inverter.
    both transformers has to use in 12v to 220V 50hz inverters.
    Kindly help me to rewind these transformers . what size coil and how many turns I have to wind.

    please give some option to attache image while comment here.

    Thanks and Regards.

    • Hi Paaker, I am sorry, I don’t have any practical experience with transformer winding or repairing and I do not have any expertise in this field therefore won’t be able to help you with the required details.

      for image you can use any free image hosting site and upload it there and provide me the link, or you can share the same via Google drive.

  8. Dear Swag,
    i read this complete article. and i have something to clarify. nowadays i am always reading your website to learn and understand about inverters. and get ready all components except transformer. to try one by one just for experience.

    from all this articles and almost all the diagrams available on internet about inverters i have understood something about inverter transformers but in real inverters has very different transformers and connections.

    on your diagrams and articles
    the inverter transformer is very heavy.
    and it must have dual input for primary.
    and the center tap of the transformer has to connect the Battery Positive line.
    secondary line will be 220V direct output.
    almost every inverter diagrams show like this.

    now i have a fully working Chinese 300W inverter. i just open and see inside. it has very small transformer but its not giving direct 220V output. transformer has 3 pin out put and it connect to 4 IRF830 Mosfets. mosfets are giving output 220V

    i just found 2 units of Damaged UPS form scrap shop. both are same brand and it has a very heavy transformer. but primary has only 2 pin instead of 3 pin. and The Battery Positive not connect to the transformer at all. Transformers primary 2 line connect to the heat sink of Mosfet( IRF3203)
    (i cannot attach images here either i can show the pictures)

    i am confuse with Inverter transformers. can you please explain me why the 300W inverter has small transformer and giving 300watts output.
    and why second UPS has different kind of transformer.


    • Dear Paaker,

      The heavy iron core transformers are designed to work with low frequency in the range of 50 to 60Hz, which makes it possible to use it directly with a 50Hz oscillator and get the required 220V AC from a battery for operating any appliance.

      The small ferrite core based transformers are specified to work with high frequencies over 30kHz, therefore to drive these transformers we need oscillators at 30kHz, but 220V at 3kHz cannot be used for operating our home appliances, therefore this high frequency 220V is converted back to DC 330V and then back again to 220V AC. All These operations makes the compact inverter circuit very complex, and therefore the heavy iron core based design is preferred for experiments by the new hobbyists.

      similarly inverters can become more compact if H-bridge topology is used in which 2 wire transformer can be used, whereas in push pull topology the transformer requires 3 wires and involves an extra winding causing it to become slightly more heavier.

      for compact ferrite based inverter you can refer to these designs:


  9. sir thanks for or response, I search for fly back converter but I didn’t find any but can boost converter work. I also came across or formular use in designing inverter transformer. now my question is as follows. (1) finding the core area you got 18sq.cm but accroding to my calculation I got 55.2 or am I missing something. Iike u said the core area is that centre E should the centre be reduce by width or height. (2) can u explain the word stack .(3) I didn’t understand No 16 & 17 calculation that is gross area & the tongue width .(4) what do u mean by total winding area . pls explain the word bobbin .pls don’t be angry with my question thanks.

    • I am sorry I do not have any calculations for transformers above the specified value in the table…..you can perhaps try to increase the dimensions proportionately by comparing it to the available 10 amp dimension of the trafo.

  10. Turns Per Volt for 1000 watt Tranformer

    Hello sir, I’m sorry to disturb,good morning .i calculate my own turn per volt using 1000w I got 0.66.so,during dividing the 1000w by the primary voltage 12v,i then got my primary current as 83.3amp.so,my question is that, I match it from the table A, to get the equivalent thickneas of wire but there is nothing like 83.3amp,from the table A, what am seeing is only 10.961 no 83.3.i.e,the rest is 1 figure before the decimal point not 2 figure before the decimal point, so, I’m confused to know my equivalent thickness of copper wire.

    • Emmanuel, that is right, the table has max data upto 10 amps, so i am afraid higher trafos cannot be built using these tables.

  11. please sir,what I mean is that.for example, I like to use a 1000va or 2000va or any watt of stabilizer transformer, can it work and can I going to divide the watt by the primary voltage to get my primary current as per the shown example specification.(2)i build one circuit is using a 12v battery and I get 220v output.so,if I put 100w bulb and my phone charger.then,the current from the bulb will start going down completely slowly until there will be no current show n from the bulb. what is the problem sir? (3)what type of battery should I use. although,i use a 12v generator battery of 7.6amps.(4)which side of the transformer will take the thicker gauge of wire, primary or secondary.

    • Emmanuel, your calculation method is correct, you can go ahead with it.

      the voltage may be dropping due to low battery current or inadequate battery charging. Either use a larger battery upto 25Ah or try to charge the 7Ah battery optimally (@ 1 amp rate for 10 hours), and check the response again.

  12. please sir, about the nick zuein inverter circuit of 2500 to 5000w,pmw,he use a jumper.can I be able to replace the jumper with ticker gauge wire or what should I use to replace it.

    • sorry Emmanuel, I cannot comment or suggest on projects published on external sites. I can only discuss about circuits presented in this website

  13. Please sir,do not be offended, I just want to be sure of what am doing.sir,for example ,I like to use a 1000va or 2000va or any watt of stabilizer transformer, can it work and am I going to divide the watt by the primary voltage,to get my primary current as per the shound example specifications.(2)i build one circuit,is using a 12v battery and I get 220v out put.so,when I put 100w bop and my handset charger,then the current from the bop started going down slowly until there will be no current should from the pop, what is the problem sir. (3)what type of battery should I going to use.although,i use a generator battery of 7.6amps.(4)wich side of the transformer will take the ticker gauge wire, primary or secondary.

    • Emmanuel, sorry I did not understand what you meant by “bop”….please use correct English with correct spelling, otherwise I won’t be able to address or publish your comments.

  14. Hi swagatam, my name t Emmanuel.please sir,i am trying to construct an inverter, I then enter net I found your explanation about how to get turns per volt, so my question is,the Tpv,i.e.1.96v that I sow,is he constant or I have to calculate my own.please sir, may God bless you as you replied back, thanks.

    • Hi Emmanuel, the 1.96 is the result as per the shown example specifications, it will be different for different transformers depending on the frequency and the core area.

  15. Sir pls one more question, cos i need ur help. In winding the the transformer, should i wind it according to an ordinary AC-DC transformer structure (primary separate and secondary separate then laminating them)? Or i should it according to a voltage stabilizer transformer whereby after winding the primary, the end terminal of the primary is joined with the starting terminal of the secondary winding, after winding the secondary with its center tap, the end terminal of the secondary with the starting terminal of the primary forms the two output as L and N mains. Sir i hope my question and explain are clear, help me because winding transformer is my field of day to day practical, i just want know in which manner inverter transformer constructed as i differenciated above. Pls help,Thanks

    • Hi Solomon,

      you must wind it as per the standard step-down AC to DC type of transformer, and not like stabilizer transformer

      inverter transformers are exactly like our ordinary step down transformers which we normally use in power supplies…

  16. Hello sir, i have few questions to ask pls help me:
    1. I dont understand, u said divide 120va by 12v we get 10a, how does 120va come about, am confused.
    2. Which of the transformer is the battery side, primary or secondary?
    3. Which side of of the transformer contains thick wire, primary or secondary?. Pls help, thanks.

    • Hello Solomon, what is the required output voltage you need from the inverter?? You have to consider this voltage, and divide it with the battery voltage.

      For inverter operation the battery side which is the low voltage side of the trafo becomes the Primary.

      I have updated the changes in the above article accordingly.

      The battery side consists the thicker wire.

  17. Tnx u used the word primary and secondary side interchangeably,
    Is it not correct to call d 12v battery side as primary side as against ur usage sir..
    Am confused with that,
    Secondly, if I fabricate my lamination (E/I) core.
    Will i need to apply any luvrixant/paint..

    • yes for inverter the 220 side is the secondary, and for normal step down use it the primary, initially the above article was written for a step down transformer, therefore the 220V is mentioned as the primary…

      sorry I am not sure about the minute construction details because I myself referred the article from an old magazine.

  18. Why we need to consider efficiency while calculating primary current and we didn’t consider efficiency while calculating secondary current

    • when current is high and voltage is low, efficiency can get affected, and needs to be optimized, when the conditions are opposite, efficiency becomes less affected, …this is my assumption

  19. engineer Swagatam good morning sir thanks very much for ur effort to help us…I made ur circuit.. and it worked normal but when I power my TV the inverter will in drop and come up gradually… pls help….

    • Hi Sunshine,
      it could be due to initial high current draw by your TV.

      Is it an LED TV? because normally LED/LCD TVs will not draw initial high current….

  20. Hi Swagatam,

    I going to a professional transformer winding person after two days to get my 1kva inverter transformer (center tapped). I need your help. What specs should I ask him?

    should it stepdown or up?
    what should be primary voltage and current?
    what should be secondary voltage and current?


    • Hi Saqib,

      All transformers can be used as step down or step up depending on which side is used as the primary, for inverter we call it step up since its used for stepping up a low voltage to high voltage.

      dividing 1000 watt with battery voltage will give you the primary current

      for secondary also the calculation will be the same, divide 1000 with secondary voltage

  21. Hello Swagatam, Long time ago I'm now back since I was making LED with you. Now asking for your help about the transformers build home made spot weld. I have many Microwave transformers but this time I have large rectangular laminated iron core made by Honeywell was using for old military scanner. This old transformer is larger than other MOT I have. So removed old copper wires and saved for later used. It was tested connect input 120 VAC and output multi-Low voltage from 5 to 24 volt AC. So now left it down to bare iron cord clean up small amount of rust area and ready to add hi temp paint. Now, however, I'm not good on math formula to put wire wrap number of turn of 5" long X 2.625" W X 1" plus thick for primary for 120 VAC. The core measure outside dimensions is 7.1875" long X 2.4375 deep X 3.4375" height. Output Secondary using 0/4 wire welding cable possibly 2 or 3 turns would be less that 2 VAC which may be high amp.

    I know I see you don't deal with Transformer Calculation I read on your post.
    If all else to give me number of turns for 120 VAC for primary and size of wire gauge recommendations.
    So the electronic math formulation is complication as I read about which I'm confused!
    So I explained above about the iron cord is laminated rectangular with round edges outside corner with opening
    square rectangular inside dimension is 5.25" X 1.5". I was not able to add picture in this post to let you see.

    Please let me know if you know someone read my post.

    Thanks again,
    John Hungerford

    • Hi John, I really wish I could help you with the calculations, but just like you I am too not good with transformer calculations, and moreover the data presented in the above article is restricted to max 8 amps only, while your trafo seems to be above this range.

  22. hello dear swagatanm
    i would like to ask you if an inverter output is 24v and i need 220 v for my home supply the creation of my toroidal transformer i have to create first the 24v winding as primary and then the winding of the 220v because in the toroidal transformer the one is on top of the other
    also i have a swg table that says the curent the diameter the gauge of the wire if you wish me to send it to you thank again for your help

    • hello demiliza, I cannot suggest about transformers since I do not have much practicals experience with them, however as far as I know the winding pattern is not too critical, although preferably you should wind the 220V winding first and then on top of it wrap the 24V winding.

  23. Pls sir help me out. I can't understand where you got these values "CA = 1.152 ×√ 24 × 10 = 18 sq.cm
    We select CRGO as the core material" and the meaning of CRGO. Pls if you can upload the picture of the core of the transformer you measured maybe that will help me understand it better. Thanks

  24. Am Andrews Kumah

    Pls sir help me out,what I don't understand in your calculations is this "CA = 1.152 ×√ 24 × 10 = 18 sq.cm
    We select CRGO as the core materia". That is, I don't understand where you got the values and also the meaning of CRGO.

  25. Hi sir, I tried calculating the specs for a 5kva inverter transformer using 48v dc supply,freq.50hz, output voltage 220 but what I get as the amperes is out of the table so I could not determine the wire gauge.the highest ampere on the table is 16.6. Can you help me out sir please if possible with the specs. My email. mrzakson@gmail.com. Thanks

  26. hello.
    our sg3525 inveter when i move the pwm verible so the pin1 vollatge is also chnage so plz tell what is problem in our inveter pin1 i connect with pin9
    baber khan charsadwal

    • I don't remember the internal configuration of the IC so can't suggest exactly about the issue, however you must check the voltage at the output pins of the IC…the voltage at the o/p pins must vary in response to PWM variations and that will confirm the proper working of the IC…..but pls remember that this reading will be the average voltage not the peak, the peak will be away equal to the battery voltage

  27. sir what is 42 as constant in transformer design means ? How does that constant forms ? I am giving one example of a transformer design in the link given below in which the transformer design uses that constant..

    i had a 300 W step down transformer with 5 primary terminals and 4 secondary terminals…. i have deassembled the transformer and done the primary winding part… i have the following doubts .. please clarify those…
    (1). According to the video

    the area of the core portion is

    so no. of turns per volt =
    42 constant/21.42 = approx. 1.96…

    hence no. of primary windings needed = 230 × 1.96 = 450.8 = 451 turns

    and no. of secondary needed = 16 V × 1.96 =31.36

    Are these calculations are correct ? Should i have to select 240 instead of 230 in calculation which will result in increase in no. of primary turns…

    (2). Which configuration of secondary will be better a centre tapped one or with one normal possitive and grnd configuration ?

    (3). how to take 32 V output from the centre tapped config. ?

    • RT, I can't confirm it because I don't often deal with transformers, so although I might have studied the calculations long ago, by now I have forgotten them…

      however the formulas given in the above article are absolutely correct and you can follow those accurately.

  28. dear brother
    I want to make a 800-1000w transformer for ips. I have bought all component to make it.
    here is the list.
    SWG 21 for primary winding,
    SWG 12 for secondary winding,
    4.5 inch
    The transformer is make by 12-0-12V secondry and 0/N-140-220-260V
    Plz help me to find out how many turn will be in primary winding and secondary winding

  29. Hello Sir

    Sorry of asking you again.But I want to know how to make mains transformer with using Toroidal core.I attach Core image and core manufacturer Test certificate. Can you please help me with that information i providw core size is OD-100mm, ID- 60mm and Height-50mm core wet about 1.842 KG (M4 CRGO material)

    • Sorry Sandeep, I have no idea about transformer winding, you should consult a transformer winder or manufacturer for all the details

  30. Hey! I've a ques about 12v battery inverter that can we use 15-0-15 transformer instead of 12-0-12 ?? will it work ??

  31. you can use any desired rated trafo, it does not matter… the output wattage will be reduced or increased depending on the current of the trafo

  32. Hello Sir. I am amateur in this field. I want to design a Transformer or a circuit that produce 12v 30am that control my DC motor. Or

  33. Sir I have 12kva automatic voltage stabilizer 50 to 220v make sir please their turns and bubain size tell me

  34. Thanks sir
    And please tell me how to make 100W dummy load for testing transformer secondary voltage and current.
    and tell me if my transformer is 22-0-22/3A=132VA if i used single 0-22 out its current is 6A or 3A and with 0-44 current should be 3A or what i am bit confused.

  35. Thanks Sir
    How to check Transformer secondary maximum voltage & current through dummy load
    for example if I have step down transformer with 22-0-22 Vac/3A=132VA how to check this with loaded out please give details.

    • Hi Sandeep you can simply do it by using your digital multimeter at the AC volt and AC current ranges respectively.

  36. Is your SWG table is accurate.Because to many on online. can I design transformer with Constant 42 for example 42/18 =2.33 turn per volt

  37. Calculating Gross Area we get = 18 / 0.9 = 20 sq.cm
    my doubt is 0.9 is constant value or how did you got this value. thanks in advance

  38. Hi, tried to comment before but don't think it worked. My question is- can I use a toroidal transformer in a push pull configuration? I have seen a 300va 115v/230v to 12v toroidal. It's a dual primary dual secondary wound transformer. If this is possible am I right in assuming I will only be able to use it at 230v at 150va?

    • Hi, yes you can use it by connecting it with a matching inverter circuit.

      all types of transformers can be used for making an inverter, there are no restrictions in this regard.

    • Thank you for replying so quickly. Was I correct in assuming only half the rated output of 150va at 230v. My reasoning is the dual secondary 12v windings in series to give 230v on the primary. However each 12v singly can only deliver 150va

      • 12V in parallel might give you better response at the 220V side….so you can make the two 12V winding in parallel and use a H-bridge inverter circuit to get the best possible results, using single 12V winding will give you 150 watts only

  39. Hi i am wondering wether it is possible to build an inverter with a toroidal transformer. I have seen a dual input dual output 115/230v to 12v at 300va that is 2 times 12v at 150va each. Would this work via the push pull circuit.? Any advice is much appreciated. I'm assuming if it is possible I would only be able to use it at half its rates output of 150va at 230v

  40. Helo sir,
    I want make 230v to 120v 1500watts step down transformer,how will calculate,SWG of primary and secondary,and number of turns,primary's and secondary's.please send details to my mail eeemani09@yahoo.com.

  41. Also tell me sir,why did you multiply total winding area to 1.3 ,and what is insulation part,and why you multiplied, why not you added it?

  42. I am not getting understand that how to understand about winding area,ssuppose I completed total no. of turns, but how to know that this winding area will match to calculated winding area?

  43. Hello sir,plz tell me which type of area in sence that primary and secondry winding area are to be maitained,i.e circular,cylindrical or other types?please tell me

  44. Hello Swagatam, My name is Tobi. Thanks for the tutorials. I'm an Electrical/Electronic Engineering student and I love electronics so much. I've been trying to design an inverter of 100watts or more, just for my personal use. I've seen a lot of inverter circuits on google and youtube but each time I simulate them on my circuit wizard software, they don't work properly. So please can you help me out with a cool circuit that works fine or give me a link or something. I'm very good with theories but I want to be good with practicals as well. Please I really need your help. Thank you.

    • Hello Omoregbee,

      All the circuits that you have tested on the simulator were probably good…because it's your "wizard" that's not efficient enough to check their results, so leave it aside and try one of the selected inverter designs practically, that's the only way you'll learn things correctly.

  45. Hello boss! Hope everything is going smoothly. Am sorry I promised to notify you(7,dec.2013). The circuit(oscillator,power stage) worked,and I have been using it, thanks once again,it was because of your assistance,I sincerely appreciate. Can I connect two identical transformers in parallel (center taped) to my inverter? My aim is to multiply the wattage. Extend my regards to your family.***Ahmed***4rm*****NIGERIA*****

    • You are welcome Boss!
      yes you can connect two transformers in parallel but only for the primary side….the secondary must be used and terminated separately to separate loads.

  46. Dear Sir ,what do we mean by the primary and secondary winding area and what is its significance while winding?

    • dear prathamesh,
      the winding area determines the specified number of turns that it can accommodate optimally…that's the only significance it has.

  47. Can I use Ferrite core for 50 Hz inverter transformer?
    If yes give winding details for a 9-0-9 / 230 volt 500 VA transformer

    • ferrite cores don't work with low frequencies, it will require a minimum 10kHz for proper functioning, so it's not possible

    • Can I connect solar panel to an inverter without a battery?
      I have 6×12 volt 100 watt solar panel and a 12 /230 volt 500 VA inverter.
      Any simple circuit ?

    • yes you can do that, but make sure that during peak sunshine the panel voltage does not become too high than the inverter specifications.

    • My inverter circuit board has LM3525, LM 339, 12F508 ic's and IRFZ 44 Mosfets . It is square wave output. Can I change this circuit with adequate components to get pure sine wave out put. If so please give the circuit. Expecting your valuable reply soon.
      Thank you

    • it could be a modified sine wave or pure sine wave equivalent, can't say with confirmation, although the presence of a microcontroler IC 12F508 and also opamps LM339 indicates a highly sophisticated circuitry which could be a sinewave inverter

    • I am sure, it is not a sine wave because when I connect an inductive load like fan, a humming noise is produced. Your sine wave inverter circuit using TL 494 is very simple. If any kit or assembled board available online using this circuit please inform details or link

    • OK may be it's not a sine wave inverter then.

      Sorry I do not have a kit or assembled board for solving this problem, you may have to inquire it online or in the local market

  48. Hi Vijeesh,

    you may be right, as per the chart 12SWG should be used for currents not above 10amp but this may be under ideal conditions which will ensure no heating up of the trafo even under full load, however 66 amps is way too high and using 12SWG could be dangerous for this much current.

    although I am not an expert in this field, it looks quite obvious that 66 amps will simply smoke the transformer if a 12SWG is used, or perhaps the person may use many 12 SWG in parallel, that could be a valid possibility, and that would be quite OK….suppose he uses 5 nos of 12SWG strands in parallel then it would just do the job.

  49. Hai Sir good morning,
    Last week I went to a local transformer/inverter maker for a 800 watt 12-0-12 transformer for an inverter project,he said the primary will be 21 gauge and secondary will be 12 gauge,because of his reputation for supplying good inverters I gave the order for the transformer.as per above calculation 800 watt/12 volt is 66 amp but the chart is saying 12 gauge can carry only 10amp.He is giving a surety that it will carry 800 watt load.What is the trick they are using.

  50. Hi sir,
    In calculating turns per volt, Is the 1.3 a constant no? Does this refers to the magnetic flux density or the saturation of the core?

    • Hi Jerico, it's the flux density and is constant, you may refer to the following post for a detailed info:


  51. sir,
    the article is really interesting. In order to design a distribution transformer, will the core designing be same as sir has done? Or is there any difference? if so, i would like to request your kindness to elaborate on it.

    • Hi Dozo, yes since all transformers are basically intended for controlling voltage and current parameters, their design calculations will use the same standard formulas and systems.
      However the range provided in the above article is quite limited and it won't probably have the essential data for a distribution transformer.

  52. Pls I will like to know the type of transformer that can be used for 1kva inverter and also the rating of the transformer. Thanks

    • divide 1kva with the battery voltage to get the transformer secondary current. the primary voltage will be as per the specs of your country.

  53. Thank you sir for replying,, actually I am stuck with giving the time delay for the igbt switches in a dual half bridge inverter config. Its for simulation purpose….. because of the dual config. m always getting wrong o/p. please suggest anything.

    • you mean dead time? It's internally fixed in the IC, You can refer to the following diagram for some clue:


    • getting it online will be difficult, you will have to find it locally in your area, or in your nearest electronic market

  54. Pls sir. I want you to help me with the calculation for 1kva transformer inverter. I used the above method but the challenges was that I couldn't find the wire thickness from the table you gave above. Please I will be very grateful if u can upload a table that will start from 1 and not 10 for both thickness and lamination. Or if there is another way of doing the calculation let me know sir. Hope to read from you soon.

    • Thank you khennie, but I am sorry I won't be able to help you with the calculations because I too have no idea regarding the wire SWG calculation which would handle 1000 watts. I got the above data from one of the electronic magazines and I personally do not have any info regarding the specific data that you are asking.

      I would advise you to seek the help of a professional transformer maker, he would charge a bit but finally you would be able to achieve the perfect design as per your requirement.

  55. I really appreciate your tremendous effort in help others out. Please sir, I want you to help me calculate the core size for the primary and the secondary, number of turns, the lamination size for 1kva transformer for inverter. I tried using the method you used above but I halted when it comes to choosing thickness of wire for the secondary in the table because I couldn't find there. Please sir. I want you to give me the wire table that starts from 1 and not 10 and also that of lamination table. I had be very grateful if you do that for me sir. Hope to read from you soon sir.

  56. i have an 200watt inverter with two irfz44n mosfets. how can i increase its power to 400watt.? can i add more mosfets in parallel? plz reply soon.

  57. Hai Sir,
    For secondary winding should we double the turns that is 49 centre tap 49 total 98 turns or after 24 turns should we take the centre tap and again wind another 24 turns.

    • Hi Vijeesh,

      please explain your question detail, I could not understand what specification you are trying to make.

    • In the above calculation you got 49 turns for secondary winding.(means in the secondary winding first we will wind 49 turns with 12 swg wire then we take the centre tap then again wind 49 turns,total 98 turns) or we have to take the centre tap from the middle of 49 turns that's after 24.5 turns we take the centre tap and again wind 24.5 turns.

  58. Please do design a 5Kwatt inverter transformer.

    this will be much more needed since we are all globally going for green energy. And 5kwatt inverter is much sought after, than low power inverter.

  59. well I am making an inverter which should be of 100 watt using 12v 7Ah battery. Can you tell me a circuit, also I am a beginner in making inverter.
    Also my teacher insisted me to put an cooler( i dont no why) off coarse a fan, but i told them that it is not necessary but he made it strict to add an fan. so can you tell me how to add a pc fan to an inverter circuit.
    it would be a great help.


  60. hi,
    can we make an inverter for very small voltages like .5 volts using amplifying transistors like 2n2222 or 2n3904, and the output should be around 3-4 volts ac, that can power 2 leds. if yes can you tell me such a circuit. also about transformer, how does it is built for such a low voltage ?
    i need it because i am participating in inspire award.

  61. Ahmad, don't bother about such details, concentrate on the basic technique and use only the three leads of the mosfet,

    use the metal tab for attaching heatsinks only and nothing more.

  62. 6.8v trafo will give 400v at the output, you will need to adjust the PWM pot or the load correction pot for adjusting it to 220V.

    You can try 12v or other trafos also, if you wish.

  63. Ahmad, I have checked the link, yes you can use 200K + 100k variable preset a pin#6.

    first try with single mosfets only…if it works perfectly then you can add one more mosfet in parallel on each channel.

  64. Your link did not open the circuit page, it opened the homepage of the site….provide the exact link of the diagram, only then i would be able to say anything.

  65. Thanks Ahmad!

    By default the 104 caps can be 50V rated, the resistors 1/4 watt rated. I am not sure about the resistor replacement of 200K…can you show me the exact link?

  66. You don't need to rewind the 1000watt trafo, you can use the same trafo for obtaining lower wattages…the optimization will simply depend on the battery current which can be reduced as per the requirements.

  67. Dear Sir,

    i have a question, suppose i will get an inverter and ups with same rating including batteries, will they give same back up time.
    waiting curiously for your reply

  68. Sir,

    i have just salvaged 2 Nos of ups transformers from an old working UPS "Luminous 750va" double battery, i just want to know that can i use them to build an inverter with a range between 200 to 500 watt power inverter for home. second is that i am confused about the connections of these transformers there are 7 wires coming out from one side and three on the other side. how to identify the wires and check their voltages. i have been posting this every where but i idint receive any response. i shall be grateful if you could help me resolve this thing. the transformer has this marking on it " TX-201-1000-02"

    • Gowhar, While removing you could have at least noted down which taps are terminated as mains outputs for the appliances.
      Anyway, you can connect your home AC mains across the different taps of the trafo randomly with a 100 watt bulb in series….the taps which produce minimum glow over the lamp could be assumed as the 220V winding of the trafo….

      Once you locate this you can keep the mains input with the 100 watt series bulb connected, and take a DMM for checking the AC voltages across the remaining taps…in this way you can go ahead with the required identifications.

  69. hi friend,how are you and your family.my friend,I want to make a transformer for ups to charge 200 amps battery in 30 minute approximately and give good back up and drive about deep freezer (triplet) an water-pump and five fans,five energy savers at once.please
    help me my friend.

    • hi imam,

      you are probably looking at a 10kva inverter design, i have no idea how to design such a huge transformer, please consult a professional trafo designer

  70. yes, I think the above data is limited for upto 20 amp transformer not above that, so im sorry a 1kva could be too large and not within the range of the above data.

  71. Hello Everybody.

    Can someone tell why the factor 1.152 is used in calculating the core area? where did it come from. and if possible, is there a formula to be used that states the core area depending on the frequency. I'm asking because i want to use high frequency transformers and i need to know what size for wha tpower

    • Hello Gober,

      The above explanation is solely for iron core transformers not for high frequency ferrite transformers…so the calculations won't work for you.

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