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To reduce the cost and size of the power converters, techniques of reconstructing three-phase current through a single current sensor have been employed in permanent-magnet synchronous motors. In existing studies, the reconstruction precision is largely affected by current reconstruction dead zones in the space vector pulsewidth modulation (PWM) plane, which requires additional algorithms to compensateeither by modifying PWM modulation strategy or by phase-shifting of PWM signal. In this article, a phase current reconstruction method for three-phase inverter with the modification of a twelve sector space vector pulsewidth modulation (TS-SVPWM) is proposed. By arranging a single current sensor on a circuit branch between two power switches, the proposed method can reconstruct the three-phase current of the voltage source inverter and avoid the dead zones located at the sector boundary region. This method can be realized not only with a single Hall-effect current sensor but also with a single shunt resistor, which can expand its application. The proposed method can be a fault-tolerance solution when there are phase current sensor faults. Beside, the three-phase current can be reconstructed when there are open-circuit faults in the power switches. Compared with previous methods, the proposed TS-SVPWM can reduce the phase current harmonics. The effectiveness of the proposed method is validated by experiments. [ABSTRACT FROM AUTHOR]

A failure of insulation is one of the main reasons for electric machine outage. Online condition monitoring (CM) of an incipient degradation of turn insulation could eliminate the potential fault at the early stage, which is attractive but challenging. To improve the sensitivity and availability of CM, a noninvasive technique is presented in this article for the inverter-fed electric machine utilizing the existing high-frequency (HF) switching oscillations during pulsewidth modulation operation. First, the tail component sensitive to turn insulation is selected among the dominant oscillation modes in switching current, which can penetrate the winding of machine within an adequate frequency band (e.g., several hundreds of kHz). Then, a noncontact and simple HF sensor is developed for switching oscillation current capture. The CM system, procedure, and turn insulation state indicator are devised. After that, experimental work is carried out on a 3-kW permanent magnet synchronous machine test rig. The results show good sensitivity (about 2%) to the local incipient degradation of turn insulation with insusceptibility to the operating conditions. Finally, further discussion is given to demonstrate the performance of the method. [ABSTRACT FROM AUTHOR]

Recently, dual three-phase drives have attracted an increasing attention with their high torque density, improved fault tolerance, and direct use of the off-the-shelf three-phase inverters. This article presents a carrier-based algorithm for the selective elimination of high-frequency pulsewidth modulation (PWM) torque harmonics in dual three-phase drives. The PWM control of the power converters is one of the main sources of high-frequency torque ripple in high-power electrical machines. The proposed technique selectively eliminates the torque-ripple harmonic components by applying a proper carrier phase shift between the two three-phase subsystems of the dual three-phase drive, considering the arbitrary phase displacements among the two subwindings. Two case studies of dual three-phase machines with phase displacements of 0 and π/6 are, respectively, analyzed under the most significant carrier phase-shift solutions. The torque performance improvement and the effect on the current ripple introduced by the proposed carrier phase-shifts are presented and validated by means of numerical, finite-element, and experimental results. [ABSTRACT FROM AUTHOR]