Re: [femm] Linear induction motors

["Eckart Nipp" <eckart.nipp@xxxxxxxx>]

Hello,

just some thoughts concerning the saturation problem mentioned.

A flux density of 3T and higher in machine steel sheets is
actually not impossible if only the field strength H is high
enough. Such flux densities occur for instance in the cores of
magnetizing devices for rare earth magnets.

An easily made mistake that can lead to irrealistic saturation
levels is mixing dimensions like inch vs. mm. Also the currents
should be checked if there is not a dimension error. That happens
easily when you alter the number of turns, the interconnection of
coils, the number of slots per pole and phase, or such.

Concerning the magnetization curve, adding a point at very high
magnetic field strength is a good idea. I use that since many
years in various programs. However, consider that the slope above
the already given curve tip should be similar to that of air, not
the absolute permeability of this additional point. Furthermore it
was found that the differential relative permeability of steel is
larger than unity even at very high saturation levels. It may thus
be more realistic to compute this extra point with a slope of a
relative permeability of e.g. 5.

Greetings
Eckart