
Electric Motors 15
We note that the first stage of evolution (Figure
1.8(b))
results in the original single gap of length g being split into
two gaps of length g/2, reflecting the requirement for the
rotor to be able to turn. At the same time the single mag-
netizing coil is split into two to preserve symmetry. (Re-
locating the magnetizing coil at a different position around
the magnetic circuit is of course in order, just as a battery can
be placed anywhere in an electric circuit.) Finally (Figure
1.8(c)),
the single magnetic path is split into two parallel
paths of half the original cross-section, each of which carries
half of the flux, an ...