Let us consider a synchronous generator (Gn), which
is n time larger in both axial and radial directions of
a generator (G1). The air-gap magnetic induction in Gn
may be assumed to be same as that in G1. Since magnetic
flux is considered to be proportional to surface
area, the magnetic flux of Gn is n2 times larger than that
of G1. Since section area of armature conductor is
considered to be proportional to product of perimeter
and radius, the area of Gn is n2 times larger than that
of G1. Therefore the output capacity of Gn is n4 times
larger than that of G1. The volume of Gn is n3 times
larger than that of G1. The loss of generator is considered
to be proportional to volume of magnetic material
and conductor one, then the loss of Gn is n3 times larger
than that of G1. The output power is proportional to 4/3
power of volume. The loss is proportional to 3=4 power
of output. The larger generator of similar figure is better.
This is scale merit. However, real generator is not
similar. It is because surface is proportional to n2 though