Guys can you tell me that how can I calculate transformer winding?Example:- I need (12volts, 4Amps, 50Hz on Secondary's side of transformer and give 230volts 50Hz on Primary's side of transformer) how I calculate the wire's number of turns? In this case I can give different values of current like 1Amp, 2Amps, 3Amps etc on Primary's side of transformer. But I need constant 12volts, 4Amps, 50Hz on secondary. So how can I calculate.Please give an answer with an example basis on (0-12) transformer.
Basically, the ratio of voltages is the same as the ratio of turns. The currents are the inverse ratio but that kind of takes care of itself if you just deal with the voltage ratio.
As others said, only worry about the voltage ratio. That determines the turns ratio. Current doesn't enter in to this equation yet. The minimum number of turns on the primary is dictated by two things, the saturation flux density and magnetizing inductance. Flux density is proportional to the applied voltage, inversely proportional to frequency and effective area of the core. You'll need to know the saturation limits for the core you are using. You also need to have a minimum numbers of turns to minimize the no-load current which relates to magnetizing inductance. My rule of thumb is the inductive reactance must be 5x the maximum expected load resistance, however, for a AC mains transformer, this is often a hard number to quantify since the load can be near zero. Next is wire size. You will need to consider proximity effect losses as well as DC losses. You'll find that there is an optimum wire size for the windings, but for a 50Hz transformer, you'll probably use a wire diameter smaller than optimal for a low power transformer. I suggest reading about this in Ferrites for Inductors and Transformers by Snelling and Giles. You may need to make compromises to meet your needs. This is where the current supplied by the transformer comes in to play, maximum heat loss expected. While making your own transformer is educational, for power mains transformers, you are better off buying one or scrapping it from an old piece of equipment.
