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28th December 2011, 02:24 PM  #1 
diyAudio Member
Join Date: Dec 2011
Location: Philippines

Here is the Computation of EI core Transformer Philippines Base
The Power transformer
my Example is the Primary is 220 volts (Philippines Base) but you can Deduce it by Dividing by 2. the Secondary is 12012volts or 012volts 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 see at Table 1 and Table 2 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 (PHILIPPINES Base) 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: note: I = Current, W = Wattage, E = Voltage 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 
31st January 2012, 07:43 PM  #2 
diyAudio Member
Join Date: Mar 2008

What is center leg and thickness? and what is the unit for what? (Inch or mm)??
I think center leg is, center of E part(core) witch is in the middle and winding(primary and secendery coil) around this and thickness is total core stacking. this table is very useful if i understand. 
28th February 2012, 05:50 AM  #3 
diyAudio Member
Join Date: Jan 2006
Location: makati

Transformer cores are measured in inches. You're right the pages are old but still useful.

20th December 2012, 04:49 PM  #4 
diyAudio Member
Join Date: Dec 2012

what do you mean by philippines base is that related to the core size?
What is center leg and thickness and what is the unit, they are used for what? and what is the corresponding core size fore the calculated transformer above thanks for your help. 
28th January 2015, 09:34 AM  #5 
diyAudio Member
Join Date: Aug 2013
Location: Cebu City

is there no other formula?coz i have that kind of table here but only for 1000 watts trafo.i want to make 3000 watts of trafo.

28th January 2015, 01:41 PM  #6 
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders

The table on the left is using an EI core flux of approx 0.5T to 0.7T
This is a good value to use for an unknown material. Once the transformer is built, you can test the Primary only (no secondary wound yet) to determine the actual primary no load current and from there determine the maximum usable Flux for the material you have.
__________________
regards Andrew T. 
28th January 2015, 01:43 PM  #7 
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders

The table on the right seems to be using ~3A/sqmm for the copper windings.
Modern transformers seem to use a higher current rating to save money on the copper in return for lower performance.
__________________
regards Andrew T. 
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