
Electric Motors 11
the flux will subsequently take the easy route through the
iron, some will still leak into the air, as shown in Figure 1.4.
We will not pursue leakage flux here, though it is sometimes
important, as will be seen later.
Air-gap flux densities
If we neglect the reluctance of the iron parts of a magnetic
circuit, it is relatively easy to estimate the flux density in the
air-gap. Since the iron parts are then in effect perfect con-
ductors of flux, none of the source MMF (NI) is used in
driving the flux through the iron parts, and all of it is avail-
able to push the flux across the air-gap. The situation depic-
ted in Figure 1. ...