High-Fidelity Magnetic Characterization and Analytical Model Development for Switched Reluctance Machines

This paper proposes a new experimental procedure for magnetic characterization of switched reluctance machines. In the existing methods, phase voltage and current data are captured and further processed to find the flux linkage. Conventionally, assuming zero initial flux value, the flux linkage can be found by integrating the corresponding voltage term. However, the initial flux value is usually unknown, e.g., it can be nonzero when the current is zero due to the residual flux effect, and, thus, imposes error in magnetic characterization. The proposed method addresses this issue by considering an additional equation in steady state. This method injects a low-frequency sinusoidal current to one of the phase windings when the rotor is blocked at a given position. Since the phase is excited by a sinusoidal current, the averaged flux over an excitation cycle is zero, even though the residual flux and core loss exist. This additional equation together with the voltage integration make it possible to avoid errors associated with the core nonidealities and accurately solve for the magnetic flux. Furthermore, an analytical expression is proposed that precisely fits the magnetic curves. The proposed characterization methodology and analytical model are verified using the experimental results from a 3-phase 12/8 switched reluctance machine.