about bh curve

The warning that ANSYS gives is if the final value is less than free space, because depending on the final values it can even be negative. It does not give a warning if it is too large, which can easily lead to an over estimation of the effective reluctance and as a result the torque.

For nonconvergence issues, there are some areas to review:
1) Plot the Nu-B2 curve for the BH data and make use there are no
oscillations in the curve, since the deriviative of this curve is used in
the solution process. Oscillations will produce convergence problems.
2) In regions which are saturated, a coarse mesh will cause problems.
Check the problems which did run and see what the MURs are those elements,
particulary in regions in which the flux is changing directions, like in
corners. If it indicates that the elements are saturating and they are
coarse, then they should be refined. This is especially a problem in which
the BH data has a large slope in the linear region, say 10,000.
3) You could increase the number of iterations. If the monitor shows that
the residuals are being reduced as the iterations increase, but it just
seem to run out of the iterations, increase the limit using the NEQIT
command
4) You could increase the convergence criteria using the CNVTOL command for
the AZ dof, which is the one which usually has the problem. The default is
.001 in this command. You can use what value is occuring at the end of the
iteration that it is stopping at. If the problem is oscillating about a
large value, this is not a good approach.
5) If none of these work, you can try the transient, but if the elements
are too coarse in which the flux is changing directions, the transient
might not converge either.

·         The B-H curve should cover the complete operating range of the material. If a point beyond the end of the curve is required, the B-H curve is extrapolated with a slope equal to the free-space permeability. You can view values in the extrapolated region by adjusting the X-axis range. To do so, use one of the following together with the TBPLOT command: