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27th December 2011, 04:08 PM  #71 
diyAudio Member
Join Date: Dec 2011
Location: Philippines

The Power transformer we are going to compute specifies 12 volts output with 750ma current (my Example) converting milliamperes to ampere will give us. .75a , multiplying voltage by current gives us wattage or power.
12x.75 = 9 watts after having solved for the wattage of the transformer, which is 9 watts, look at Tables 1, where 9 watts is listed, follow the table horizontally and pick up the date for the center leg, thickness and turns per volt. Center leg  3/4 thickness  3/4 turns per volt  10 the nest step is to compute for the number of turns for the the primary and secondary coils respectively. the number of turns per volts in the primary is equal to the number of turns per volts in the secondary. Primary coil  220 volt (base our voltage rating in our country which is the PHILIPPINES) Secondary coil  12 volts Number of turns (primary) = 220x10 = 2200 turns Number of turns (secondary) = 12x10 = 120 turns having computed for the number of turns in the primary and secondary coils. determine the sizes of wire for these coils in the next step . before computing for the guage or size of wire (AWG) must find out the current capacities of wires and their corresponding sizes. this data is provided in table 2 . the power formula is used again in solving for the currents of wires in the primary and secondary. dividing the watts over voltage gives us the current of the wire: I = w/e I secondary = 9watts/12volts = .75 a I primary = 9watts/220volts = .04a after having solved for the currents of wires pick up the corresponding sizes of wires from table 2. choose the closest current listed in the table. Size of wires (Primary)  #35 Size of wires (Secondary)  #23 in case of a multivoltage secondary, the higher voltage should be taken for computation. if the transformer has multiple secondary coils, the wattage of each coil is computed and then summed up. in other words, the wattage of the primary is equal to the total wattage of all secondary coils. if the secondary coil is only centertaped, half of the wattage and current is taken to compute for the wattage of that coil. the primary is 2200 volts, the secondary is 12012 volts 
2nd January 2012, 12:42 PM  #72 
diyAudio Member
Join Date: Jun 2010
Location: Near the Mountain

Thanks tranqspogi, its useful for me...
our primary is the same that is good but I guess the frequency is different. Right here in Indonesia that is 50Hz, so my trafo need more turn for same T. Btw I want some opinion about the "red paper" that I attach, I want to use it, or maybe you can tell me what paper did you use to make your transformer? or some picture of it Regards
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3rd January 2012, 01:01 AM  #73 
diyAudio Member
Join Date: Sep 2010
Location: Grove, Ok.

Thank you tranqspogi for the great information and excellent examples.
But I would like to know where I might be able to access the tables that you have pictures of??? I am sure the internet has them somewhere, but it would be bennificial if you could direct some of us laymen to the proper website. Thank you for your knowlege. 
3rd January 2012, 04:15 AM  #74  
diyAudio Moderator

Quote:
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Do not despair, though they seem to be winning now, they always fall in the end......Gandhi 

4th January 2012, 03:37 PM  #75 
diyAudio Member
Join Date: Jun 2010
Location: Near the Mountain

ok...
now I have better feeling about it I'll be back with my latest traffo build & a few more formula
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Thank you, I wish you happy peace & G B U 
5th January 2012, 08:34 AM  #76  
diyAudio Member
Join Date: Dec 2011

Quote:
bli Nyoman pnya skema smps 500w ga? tentunya sparepartnya yg mudah dicari di jkt. 

5th January 2012, 08:54 AM  #77 
diyAudio Moderator

Riff This is an English speaking forum. Please post an English translation with your post.
Silahkan posting terjemahan bahasa Inggris. 
5th January 2012, 10:44 AM  #78 
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders

Post79 shows a translation from english that appears, very unusually, to be much shorter than the english version.
Is there something missing from the translation?
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regards Andrew T. Sent from my desktop computer using a keyboard 
5th January 2012, 10:50 AM  #79 
diyAudio Moderator

Hi Andrew the only part that was translated from English was "Please Post an English translation with your post" I find that the translation engines work best with simple sentences
The translation engine did not do a particularly good job of translating the post I referred to though, so whether my message gets through I am uncertain, but putting the Indonesian back through (always a good test) returns "Please post the English translation" So I guess google simplified it Tony. 
5th January 2012, 11:45 AM  #80 
diyAudio Member
Join Date: Nov 2011
Location: UK

This question has been asked many times and answered almost as many times.
During my HND training we were taught the following formula. Turns/Volt = (1 x 10e9) / (K * FF * B * f * Ai) Where FF is Form Factor  1.11 for Sine Wave, 1.00 for Square Wave and 1.10 for Triangular Wave. K = 4 B = Max Flux Density in mT. (780mT is good practice but anything up to 1350mT) Ai = Area of magnetic CORE in square millimeters f = Frequency And for Ai: Ai = (Square Root W) / K Where W is 110% of the TOTAL secondary power K = 0.0086 for EI, 0.015 for TU and 0.035 for Ferrite type A13 
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