PMSM Current Shaping for Minimum Joule Losses While Reducing Torque Ripple and Vibrations

Abstract

This paper presents a current shaping method for torque ripple and mean air-gap radial forceshape harmonics reduction, under minimum Joule losses, used for air-born and structure-born vibration reduction in 3-phase PMSM electric drives. The main source for structure-born noise in electric powertrains is the torque ripple, while the main source for air-born noise are the radial air-gap forces. The proposed method uses a Fourier-decomposed LUT model obtained from updating the 2D electromagnetic FE model using test-bench results. Modal testing is used to update the structural model, and the vibration response on the machine full RPM range is determined using the vibration-synthesis method. The proposed current shaping algorithm is deterministic and can be used on any topology of 3-phase PMSMs. The torque and mean air-gap force harmonics that are intended for reduction can be arbitrary selected and their minimization can be fully completed if the maximum current and voltage constraint are respected. On the machine under test, vibration reduction is accomplished, especially for the mechanical orders that interact with the second mode-shape.

Analytical model of electromagnetic torque of surface PM motors considering current harmonicsin electric vehicles

“…To simplify the theoretical analysis, the solving path r2 is taken, since the variation trend of the peak value of the cogging torque with the design parameters of the motor is identical regardless of the solving path, 22 which is verified in Figure 7. According to (5), (8), and (27), the cogging torque of the motor with skew slot is expressed as…”

“…4 The electric motors are expected to provide higher output torque and better NVH quality in these application scenarios to ensure the health and comfort of passengers, while the major source of structure-borne noise is the torque ripple. 5 The prediction of instantaneous torque value and analysis of torque order characteristics are significant since the amplitude and order characteristics of vibration and noise play an equally important role in the initial design and optimization of the motor. The non-sinusoidal PM and armature reaction magnetic fields, as well as the current harmonics, are two of the most important factors contributing to the motor torque ripple, 6 thus they deserve to be analyzed in detail.…”