Here is the Computation of EI core Transformer Philippines Base
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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 12-0-12volts or 0-12volts

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 multi-voltage 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 center-taped, half of the wattage and current is taken to compute for the wattage of that coil.

the primary is 220-0 volts, the secondary is 12-0-12 volts
Attached Images
 transformer coil mini.JPG (126.7 KB, 332 views) transformer coil table 2.JPG (144.9 KB, 334 views) winder.jpg (167.6 KB, 307 views)

 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.

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