255 – Evaluating the N-T Curve of an IPM motor Using 3D Correction

Application Note / Model Data

Overview

Since control design and motor design are designed by different designers, cooperative design is difficult. However, in order to meet the sophisticated demands in recent years, it is important to identify problems while coordinating motor design and control/circuit design at the early stages of development. In cooperative design, it is possible to utilize circuit simulation using a highly accurate plant model.
In JMAG, it is possible to create motor models that can model actual machines in detail taking into account magnetic saturation characteristics and spatial harmonics in the motor. By incorporating the JMAG-RT motor model into a control/circuit simulator, it is possible to perform coupled simulation taking into account both the magnetic saturation characteristics and spatial harmonics of the motor and the control characteristics of the motor driver.
In recent years, due to motors becoming thinner and power output increasing, 2D model approximations during plant model creation are no longer able to be used. However, by performing 3D analysis for some operating points and correcting the characteristics of the plant model used, it is possible to improve the model accuracy while suppressing the computation time.
In this example, obtains N-T curves using the correction function.

N-T curves

An N-T curve for a 3D model, a 2D model, and a 2D model with correction are shown in Fig. 1.
It can be seen that there is a large difference in the maximum torque at low speed between the 3D model and the 2D model. This is because for the 2D model the torque is overestimated because the magnetic saturation at the motor end is underestimated. N-T curve becomes the same as 3D by using correction.

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