This paper proposes a method of eliminating common-mode voltage (CMV) and shaft voltage in dual three-phase motors using the carrier phase shift of space vector pulse width modulation (SVPWM). SVPWM for the dual three-phase motor is simply implemented using two traditional three-phase SVPWM structures. The representative work of the study is to eliminate the shaft voltage by applying the carrier phase shift method due to the cancellation of CMV. It was verified that the proposed method could reduce the shaft voltage with a simple technique, rather than applying a complex algorithm to reduce it. Also, the motor current and torque behaviors are analyzed to confirm that the proposed method does not affect the motor characteristics. The proposed method has been analyzed based on an equivalent circuit model and it has been verified through the experiment that the shaft voltage is simply eliminated by applying the proposed method.INDEX TERMS Bearing fault, common-mode voltage, dual three-phase motor, pulse width modulation inverter, shaft voltage.
In this paper, parameter optimization of multi-layered interior permanent-magnet synchronous motors for electric vehicle propulsion is carried out to improve torque ripple and efficiency at low-and high-speed regions. First, we establish a torque ripple map based on d-q currents. The ripples of the d-q parameters and harmonics of the phase flux linkages are then analyzed to investigate the relationship between the torque ripple and the parameters. Second, we compose and analyze an iron loss map based on d-q currents, and then investigate the parameters that affect the harmonics of the flux density. In particular, because the high-speed region is highly vulnerable to iron loss, the parameters related to this tendency are also analyzed. Based on the analysis results, we develop a parameter optimization strategy that leads to an optimal design. To analyze the electro-magnetic performances of the motors, two-and three-dimensional finite elements analyses are carried out by employing sinusoidal and inverter-controlled currents, and the improvement achieved are demonstrated by the experimental validations on prototypes.INDEX TERMS Efficiency, iron loss, low-and high-speed regions, multi-layered interior permanentmagnet synchronous motors, parameter optimization, torque ripple.
The dynamic eccentricity fault (DEF) of the interior permanent magnet synchronous motor (IPMSM) is mainly caused by external mechanical shock. In the case of DEF, an unbalanced magnetic force occurs because the length of the air gap is not constant. Noise and vibration of the motor occur due to unbalanced magnetic force. In addition, since the length of the air gap is not constant, the distribution of magnetic flux density is distorted, and iron loss is increased. As the iron loss increases, the temperature rises, and an irreversible demagnetization fault (IDF) of the permanent magnet occurs due to overheating. Therefore, in this paper, the fault mechanism of IDF due to DEF of IPMSM for electric vehicle (EV) traction is analyzed. Initially, the magnetic flux density and iron loss characteristics according to the healthy condition and DEF condition are analyzed using the finite element method (FEM). Then, the detailed iron loss analysis is performed based on the phase current waveform measured through the load test of the motor. Finally, the fault mechanism of IDF due to DEF was verified through an electric-axle load test on a manufactured motor having eccentricity.INDEX TERMS Dynamic eccentricity, electric vehicle (EV), interior permanent magnet synchronous motor (IPMSM), iron loss, irreversible demagnetization.
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