Calculation of nonlinear flux linkage and torque for permanent magnet DC motors

This paper presents a virtual rapid analysis model (VRAM) replacing the conventional reduced order systems model for physical value calculation of permanent magnet DC brush motors. The VRAM accomplishes calculations while considering magnetic circuit saturation. Dynamic coil (current, voltage, flux linkage) and motor values (current, voltage, speed and torque) are calculated quickly and with high accuracy. In former research, the VRAM utilized 1D look-up tables to calculate each coil's flux linkage, whereas this paper investigates enhanced magnetic circuit computation with 2D tables. This new method enables the virtual work principle to compute the torque more accurately for high motor currents. Nonlinear flux linkage and torque values are almost identical to validated 3D finite element analysis, therefore verifying the model's accuracy. The VRAM can be used to optimize nonmagnetic parameters, determine torque curves or develop control algorithms. The VRAM's relative calculation speed versus conventional methods is an inexpensive alternative for research and development.