desing of step down transformer AC - AC, 220V - 5V

hi,

plz help me with the design of a step down transformer 50Hz, 220v AC - 5V AC, i = 0.5A, with high efficiency,

plz its urgent, so desperate. tnx

for sy. current 0.5a calculate py current .

assume 95 to 100 % eff.

based on va of trafrmer ,
calculate core c/s area.

assume B=1.0 and curr.density as 3 to 5a/sq.mm.

calculate Npy and Nsy.

choose appropriate SWG.

find window area.

select suitable core

if necessary , iterate the design.

srizbf
5thmay2010

srizbf said:

...assume 95 to 100 % eff....
assume B=1.0 and curr.density as 3 to 5a/sq.mm....

Click to expand...

Hi,
As I know; small transformer has never higher efficiency as so 80-85%...
By smaller transformers I would not take a higher current density as so 3A/sq.mm....
You dont have coolings surface, becomes light hot spots.
Greeting!
K.

Many questions need to be answered before a transformer design is started. Such as; What are to be the primary voltage/voltages? What is the Hz requirement? What are to be the secondary voltage/voltages? What will the secondary amperage requirements be? What type of mounting and terminals will be required? Can the unit be of open construction or does it need to be enclosed? Does the completed unit require electrostatic shielding? Will the unit be in a harsh environment? etc. I usually design a transformer for 95% efficiency with no more than a 55°C rise in temperature above ambient temperature for continuous use. This has proven to be good practice over the past 30 years. The details are too numerous to be listed here but I would be glad to design a unit for you if you wish. I no longer prototype units as I am now retired but I can be reached by e-mail at deak111@yahoo com for further info.