When comparing a large number of designs using simulations, torque characteristics can be evaluated by automatically searching for the current phase that provides the maximum torque.
In this example, a search is performed for the current phase that maximizes torque for each of 3 rotor geometries. Motor average currents and torque ripples are evaluated using the obtained current phases.
From inductance evaluation results, torque is obtained with torque formulas for each rotor geometry, and a search is performed for the current phase that obtains maximum torque. Motor torque analysis is performed with the obtained current phase, from which the average torque and ripple ratio are obtained. Fig. 1 shows the evaluation flow.
Current Phase – Torque Graph
Average Torque and Ripple Ratio
These values are calculated from the current phase showing maximum torque obtained from the inductance shown in Fig. 2.
Comparison Between Torque Values Obtained With the Torque Formula and FEA
Because the torque value obtained with the torque formula is of a fixed inductance, the value is high when compared to the FEA results that account for the influence of magnetic saturation. In this model, torque shows the maximum at a current phase of 30 deg for both FEA and the value obtained from the torque formula, and it can be confirmed that current phase values match.