making transformer

i have a few question in designing a transfoermer

1.) how did the nuimber of turns of coil affect the possible secondary output voltage. hjow about the size of the wire/coil use?
2.) could anyone help me or give some formulas to design a transformer what voltage output i want.

Just buy one. A transformer doesn't cost you much.
The output voltage depends on the input voltage and the ratio of the number of turns.

If there are 10 turns of the primary for ever 1 turn of the secondary the voltage on the secondary is 1/10th the voltage of the primary. The windings are basically two inductors wound on a common form so there is a lot of magnetic coupling. Thicker wire will allow a higher current, and the number of overall turns will increase the ability to transfer that current because the inductive coupling is higher. The form and the material you use as the core (if any) will determine what frequencies it will transfer effectivly.

sheng_james said:

i have a few question in designing a transfoermer

1.) how did the nuimber of turns of coil affect the possible secondary output voltage. hjow about the size of the wire/coil use?
2.) could anyone help me or give some formulas to design a transformer what voltage output i want.

Click to expand...

Hi,
You can buy transformer kits, if you want to wind/build your transformer.
They are supplied with coil winding data.
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Also Google for 'transformer kits' there are lots of sites.

Eric

yes there are loads of formulars for calculating transformers - we definately don't just guess! lol

the first thing you realise is that the typical example given in collage of a transformer having 2400t on the primary and 120t on the secondary doesn't make it a 240 to 12v transformer, as that formular ignores regulation (due mainly to resistance). It also ignores wire gauge completely so is the 1200t 0.1mm diamter or 2.0? even the number of turns is just a random number. a 3va transformer will have a lot more turns, a 1000va a lot less.

unless you know the answers to all those questions, and can then get hold of laminations, bobbins, wire etc - i wouldn't even bother.

how many volts are you after? at what power rating?

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For sheng_james this link will be useful before winding your own transformer.

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You need to be careful that the primary has enough turns (thus a high enough inductance) to avoid core saturation.

You also have to make sure the cross sectional area of the iron core is sized for the maxium power you will be drawing from it.

Lefty