ANALYSIS OF TRANSIENT RESPONSE OF MAGNETIC FLUX IN NONLINEAR MAGNETIC CIRCUIT.

In this paper the authors first introduce some new two-dimensional theoretical equations for the transient response of the magnetic flux in a fundamental nonlinear magnetic circuit which can be applied to the circuit containing the pole gap in a dc machine. Then they develop a numerical method for solving these theoretical nonlinear equations, in which a difference analog is used, derived from both the nonuniform grid system for space and the Crank-Nicolson method for the time derivative. Next, the transient response of the flux and the distribution of the magnetic field intensity and flux density in the pole gap are investigated for the case where a stepped exciting current is fed to the pole gap winding. As a result, it is clearly seen that magnetic saturation occurs because of a strong magnetic field intensity in the skin of the pole gap. This is caused by an eddy current induced in the pole gap, and the saturation has a great effect on the flux response. Hence, the flux response is too fast in numerical calculation results obtained by conventional linear theory, in which saturation is not considered.