[W-MB-156] Improving Motor Plant Model Accuracy by Accounting for Harmonic Iron Loss

1. Introduction
2. Motor specifications and operating points to be evaluated
3. Evaluation of loss and efficiency at each operating point
4. Summary
5. References

1. Introduction

Because of the acceleration of the motor and the effect of the PWM drive, it is becoming more important to account for loss in order to improve accuracy even for analysis using motor plant models. Particularly when the accuracy required for plant models is high, the effect of harmonic iron loss and AC copper loss (AC loss) that occurs in wires cannot be ignored.
In this document, the harmonic iron loss and AC loss obtained using a plant model at multiple operating points are compared with FEA. The effect of loss on efficiency is additionally shown. The accuracy required for the plant model determines the need to account for the harmonic iron loss and AC loss.

2. Motor specifications and operating points to be evaluated

This shows the specifications of the motor to be used, which is an interior permanent magnet synchronous motor. The shape is shown in Fig. 1. The number of poles is 8 and the number of slots is 48 (Table 1). The flux linkage is evaluated at five points from point (a) to (e) as shown in Fig. 2.

Fig. 1 Verification motor shape

Fig. 2 Efficiency map and locations of operating points used for verification

Table 1 Motor specifications for verification and operating points torque and speed (Points (a) to (e))

Number of poles/slots 8 / 48
Torque (Nm) 250, 115, 90, 75, 13
Rotation speed (rpm) 2000, 3000, 6000, 8000, 2000

3. Evaluation of loss and efficiency at each operating point

This evaluates the loss at each operating point. The results for JMAG-RT which is a type of plant model (RT), the results accounting for harmonic iron loss with JMAG-RT (RT(Iron Loss)), and the results accounting for both harmonic loss and AC loss (RT(Iron Loss+AC Loss)) are compared based on the FEA results.
Harmonic iron loss is handled as iron loss resistance on an equivalent circuit, and filter inductance is added to improve accuracy.

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