You need to calculate that from point where, limitations are in copper and they would be density off current that wire could withstand in storage environment, such as; metal storages or direct storage of the magnetic field in cupper. To much density reproduce overheating. That would be a copper limitation capacity.
Density isn't same for every diameter and diamagnetic material.
So, because limitation depends from density off the current that he can withstand, that's copper capacity, use: length, Siemens and diameter, stand for all diamagnets in magnetic field- that's amount off eletricity from battery point of view.
And it depend from interval change that have created that amount, where and how that change is stored.
Difference would be only in way off creating it:
- Where - in iron, nickel... ferromagnetic environment or directly in copper.
- How - from mechanical point of view machine need to have standard construction possibility to make 50-60 repetition in sec, the amount that need to be changed in Hz. Note that it's not same to make AC and DC in ferromagnetic environment, magnetic field density or limitations that ferromagnetic environment could withstand depends off the material and rate off the change-Hz. Also magnetization capacity off iron elements is 2,2 to max 3 Tesla, depending off material and environment.