i wish to construct a transformer with 220/120v,60hz,5watt,plz help me
Please don't! By the time you buy the special core material, the 2 types of copper wire, a good house content and life insurance for yourself, you can buy a finished and safe one from Maplin (if you are in the UK) for Pds.15.99 and that is a 45 Watt type. And finally, you say you want 60 Hz ? Then you also need 60Hz at the input, because a transformer doesn't change from 50Hz to 60Hz. Still want to know how it works? Read hyperphysics.phy-astr.gsu.edu/hba
Transformer is a thing which can reduce or increase voltage. In your question, You want to make such a transformer which can reduce the voltage is called a step down transformer. In transformer there are two coils. One is Primary and the rest of them is Second nary coil. Primary Coil is connected with input(220v) and Second nary with output(120v).To get 120v in output the transformation ratio should be 220:120 means 11:6.
The short answer is – don't. Unless you have access to exactly the right materials and equipment, not to say the right knowledge and design tools, you are risking a nasty accident if you try to make your own mains transformer. If you want to experiment with making a transformer, choose one that operates at low voltage (25V or below on both primary and secondary) and remember the following basic design rules: (1) The voltage ratio Vpri : Vsec equals the turns ratio Npri : Nsec. (2) The primary inductance Lpri must be such that its unloaded reactance, 2pi x fLpri (where f is the operating frequency in Hz) is high enough to make it look like an open circuit when there is nothing connected to the secondary. (3) To calculate the primary inductance you will need data, and possibly software, supplied by the makers of the transformer core. (4) The core must be big enough not to saturate under the proposed working conditions. (5) The windings must be able to carry the proposed curents without excessive heating. Remember that heat cannot easily escape from the windings, so the normal ratings of wire to be used in fresh air do not apply. The current ratio Ipri : Isec is the inverse of the turns ratio, i.e. Nsec : Npri. (6) You need insulation beteen the windings and the core and between the primary and secondary. This is an insurance against failure of the insulation varnish on the windings themselves. (7) The core opening(s) should be just big enough to accommodate the windings, but ideally no bigger. Once you have built a couple of successful low-voltage transformers, you might consider upping the voltage, but do read more about it first. Meantime, if you want a 5VA mains transformer, they are really cheap to buy.
