Numerical Determination of the Effective Magnetic Path Length of a Single-Sheet Tester

We describe a numerical method for the correction of the magnetic field strength and power loss values measured by a single-sheet tester (SST) based on the current method. This operation is performed by a reluctance network that yields the effective path length of the SST by determining the parasitic magnetic voltage drops over the yoke, gaps, and parts of the probe underneath the pole faces. In contrast to common magnetic circuit analysis, we enforce the magnetic flux and the magnetomotive force simultaneously and treat the magnetic resistance of the specimen as a degree of freedom. Hereby, we avoid errors due to uncertainties in the description of the B-H characteristic of the specimen and can correct arbitrary working points covering hysteretic and dynamic effects. The validity of this approach is demonstrated on four grades of nonoriented electrical steel sheets. The network is used to determine the integral magnetic path length, which enables a convenient correction of the power loss for arbitrary magnetizations including harmonics.