165 – Creating an Efficiency Map for an IPM Motor

Application Note / Model Data

Overview

Fig. 1 shows the Speed-Torque curve, and fig. 2 shows the efficiency map.
As seen in fig. 1, in the low speed region the torque becomes constant. This is due to the current controls. The torque also decreases as speed increases. This is because the current flowing to the motor coil decreases due to back electromotive voltage.
In fig. 2 it is possible to get a grasp of the efficiency at each drive condition. The range that maps the torque’s positive value and efficiency also becomes the possible range of output for this motor.

Speed-Torque curve / Efficiency map

Fig. 1 shows the Speed-Torque curve, and fig. 2 shows the efficiency map.
As seen in fig. 1, in the low speed region the torque becomes constant. This is due to the current controls. The torque also decreases as speed increases. This is because the current flowing to the motor coil decreases due to back electromotive voltage.
In fig. 2 it is possible to get a grasp of the efficiency at each drive condition. The range that maps the torque’s positive value and efficiency also becomes the possible range of output for this motor. The range in which the torque has a negative value becomes the possible range of output and efficiency for the generator mode.

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