Normally a silicon alloy sheet metal with thickness 0.35 is used in construction of transformer core that operates in 50Hz. This actually minimizes the hysteresis and eddy current losses of a transformer. First know the rating of your transformer, then you can calculate number of turns, cross sectional area of winding, insulation type and core type (core type/shell type). 

I think Samuel is right, although I don't know about the material (not regular iron?). Would add to that: my first order guess is that the energy you may allow in an amorphous core (ferrite?) is possibly lower than a regular metal sheet one. Thus you will hit saturation much faster, after which you are having an issue....  Check the data sheet for that particular core. If you have not that datasheet, test the saturation curve in  controlled experiment. But that is quite a ot of work....

efficient core material is, steel CRGO laminated sheets of 0.5mm.

u r not mention rating of transformer means how much load is fed to this transformer.

I agree with the colleagues above.

Historically, laminated sheets of iron, or crystalline alloys are used.

Now, there are these new materials that are maybe better, but (for big powers) to be used always in laminated sheets, in order to raise resistance and reducing eddy currents.

Amorphous core has been used at 50hz distribution transformers. However the material is brittle and difficult to work with. Even though the no load losses are low, the use is not widespread.

 Dear Yousry, you may find these literatures important.

 Thanks  for all specially Samuel Tesema Lakew for valuable files he sent.

The  amorphous core transfomer is widely used in China. 

Amorphous cores have been used in distribution transformers in New Zealand since the 1980's. To minimise the losses on a transformer, you maximise the cross sectional area of the core and conductor. Depending on the desired kVA of your transformer, you may need to useseveral conductors in parrallel so as to minimise eddy currents. Probably the easiest way is to use copper or aluminium foil. As you need a 1:1 turns ratio, you could wind primary and secondary coil simultaneously so you get excellent coupling.

Yousry,

Amorphous core transformers are, as of yet, not standardized as to materials properties from what I have been able to ascertain. You will need to know what the effective core cross sectional area is, the effective flux linkage path length, the volume and heat capacity of the core material. You will then need to have at hand the peak current and the saturation field for the core material along with its loss at 50Hz. Another caution is that the saturation field is a function of temperature -- if the T goes up too far the core can go into thermal runaway.... Also remember to give your design at least a 25C margin thermally above the calculated maximum core temperature; I usually go for 50C as a margin.

I strongly urge caution in using a simultaneous or bifilar winding in an isolation application!!!!

Another consideration is the breakdown voltage of the winding insulation. This needs to be at least 2X the peak voltage due to an impulse (a clamping diode or similar needs to be used on the primary and secondary to clamp the maximum impulse voltage that can be developed with a step function turn on/off like a switch). I.E. if the clamping diodes are a cathode to cathode 600PIV rectifier you need an insulation breakdown voltage of at least 1200V! This is because the primary AND secondary peak voltages can in fact be 180 degrees out of phase for a potential difference of double the clamped value. NOTE: both input and output need to be clamped!!!! A 0.1uF capacitor with a similar voltage rating (2X clamped value) should be in parallel with the clamping diodes to keep the dI/dt from being too large.

Hope that this helps,

Grover Larkins

Distribution transformers with amorphous cores are a standard product for major manufacturers like Hitachi and ABB. Metglas is the world's largest manufacturer of amorphous metal ribbon and produced material for distribution transformers for more than 30 years. Toshiba and Hitachi Metals America also manufacture a wide range of amorphous metal cores. Dexter magnetics manufacture cores using amorphous metal from various suppliers.

So amorphous metal cores would be a practical solution for your isolating transformer. Whilst low load and no load losses are of course desirable, efficiency comes at a cost. To optimise the design you need to take into consideration the cost of energy as well as the typical load cycle and of course cost of materials and labour. But if you want to minimise the size (which also minimises cost of materials), you will get higher losses.

Rather than designing your own, I guess the best option is to determine the kVA rating you require and buy an isolating transformer off the shelf like those available from http://www.indiamart.com/company/9402340/isolation-transformer.html#amorphous-core-transformer.

If you want to design your own, I may be able to assist you. But you'll need to give me some more detailed requirements.

Here's a paper that compares the total cost of ownership for dry and oil filled transformers with 'standard'and amorphous metal cores.

Here's a paper that compares the total cost of ownership for dry and oil filled transformers with 'standard'and amorphous metal cores.

Amorphous metal cores can be as  a practical solution for your isolating transformer.

rty