What is used in the core. Is using laminations in the core going to reduce flux losses in a transformer. Also have a transformer with 10,000 turns in the primary and 2,000 turns in secondary. Secondary is 24v what is the primary voltage also would a transformer rated for 75va be the most econmical choice loads that draw 20 va,15va 20 va and 5 va

 

50hz-400Hz, Lamination's are used to reduce eddy currents, (Heating effect).
The turns are a direct ratio, IOW your primary is 120v.
Your VA rating requirement will also depend on whether you are using a rectified supply and also the size of the smoothing capacitor, which has an effect on the resultant VA dependent on the continuous current and desired percentage ripple.
For higher frequencies, ferrite is usually the choice.
Max.

 

Also would mutual induction be a change in the magnetic field of one coil that can produce a emf forece in a nearby coil or is this self-inducatnce I cant remember also the va is contactor that draws 20 va a relay that draws 15 a valve that draws 20 and mics load that draw 5va. Didnt know if its best to use 75va or 100 va . Thanks