Transformer Design Information Needed

I remember from my school boy experience the you need 9 turns per volt for a one square inch core (excuse non SI units) and pro rata. That was of course with core materiel of 1940 but I don't expect things have changed much

Tables can be found on the internet listing the appropriate wire gauge for the specified currents.

The current in the primary winding will be approximately the voltage ratio times the secondary current i.e 0.8*(12/230)

Thats easy things, but you have to know your core's flux density. then youi can get the turns. If you dont know it, yhou will get wrong turn and the transforer will be burned. Syhprom is not quiet right, because he ingore the B value. This tranfermer is cheaper here, I can offer you with regulator. info@ndt.cn

I did in fact state that the core materiel was what was available in 1940 when I was a school boy, I doubt that things have changed much over the years

thanks for your reply

The relationship below might help you in designing a transformer:

Np/Ns=Ep/Es=Is/Ip

where: N - no. of turns

E - Voltage

I - current

Hi, sym you are not quite wrong, of cuase not quite right. thoery formula doesnt change any more since Farad times. Maybe there was very little soft magnetic material for transfermer. Today the silicon steel can be from 0.8T to 1.8T. sot that you will have 2.3 time difference turns. Generally we can use it as 1.2T for our counting.Of cuas different area has different turns as well. The formulas would be: V=4.44xSxBxfxexp(-4) where v=voltage V s= area cm^2 B= flux T f= frequency Hz ok you can use this for your transformer making.

"9 turns per volt for a one square inch core (excuse non SI units) and pro rata. "

Primary winding 230 V 44 mA 2480 turns wire diam 0.15 mm Secondary winding 12 V 800 mA 136 turns wire diam 0.5 mm FeSi Core 20 x 20 mm

Is that for 50 or 60 HZ ? the fluz density is about 28% higher than my calculation if it is 50HZ but core materials may have improved over the years.

I am hunting for a small un-potted transformer to take some measurements.

Without hunting for the cheapest source I find I can buy a transfomer of that spec for $15, I wonder what it would cost to build just one!

50 Hz

European Suppliers

check Mitchell Electronics for good information on transformers

they have been around for over 50 years....they mfg in NY

www.yesmec.com