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A novel 24/17-pole 3-phase stator wound field flux switching (SWFFS) machine with the combination of overlapping armature winding (OAW) and asymmetric stator poles (ASP) is proposed for higher torque density in this article. First, the air-gap modulation principle of the 24/17-pole OAW-SWFFS machine is analyzed to better understand its torque production mechanism. Second, since the torque capacity will be greatly restricted by the serious magnetic saturation which is introduced by the OAW configuration, two effective measures are proposed from two perspectives in this article to solve this problem. The first measure is to reduce the magnetic saturation directly by optimizing the area ratio of armature slot and excitation slot, and thus, the torque density can be improved effectively. The second measure is to further enhance the open circuit flux linkages, back electromotive force (EMF), and thus, the torque density by adopting the proposed ASP structure. Furthermore, the accurate ASP distances which are corresponding to the largest back EMF can be obtained effectively based on the air-gap field modulation theory. Finally, the proposed design is validated experimentally by a prototype machine. The simulated and experimental results show that about 25.7% higher torque density can be obtained when compared with 24/14-pole SWFFS machine. [ABSTRACT FROM AUTHOR]

The general rules of rotor pole and armature winding configurations combinations for 24-slot stator wound field flux switching machines (SWFFSMs) are investigated thoroughly in this article. Meanwhile, based on the virtual coil method, a novel general auxiliary evaluation variable, which is proportional to the fundamental amplitude of open-circuit flux-linkage of armature coil is proposed in this article. Hence, these SWFFSMs with larger open-circuit flux-linkage and back-EMF can be obtained effectively. In addition, the effect of rotor poles on the complementarity of armature windings is analyzed so that more sinusoidal and symmetrical back-EMF can be acquired. Furthermore, for these SWFFSMs with larger open-circuit back-EMF, the torque capability is restricted to a considerable extent due to the deep magnetic saturation caused by overlapping armature winding. Hence, a new method by optimizing the ratio of armature slot area and excitation slot area is proposed in this article to ensure that the higher torque density of selected SWFFSMs can be maintained. To verify the validity of analysis and methodology proposed in this article, seven representative SWFFSMs are chosen for verification at no load by the finite-element analysis (FEA) while a 24s/17p SWFFSM with the highest torque density is chosen for further verification at on-load conditions by the FEA and experiments. [ABSTRACT FROM AUTHOR]

The traditional direct toque control (TDTC) for induction motors (IM) is afflicted by large torque ripple, high current total harmonic distortion (THD), and variable switching frequency. Recently, some improved direct torque control (DTC) methods have been proposed to address the above problems, but they often suffer from obscure concept, intensive computation, and poor robustness. To further improve the performance, this article proposes a DTC method based on minimum voltage vector (VV) error. The proposed strategy effectively optimizes the duty ratio of fundamental VV to minimize the error between reference VV and final VV imposed on motor terminals. The optimization algorithm dose not increase the system's complexity much and can be intuitively understood by a graphical interpretation. Experiment comparisons between the proposed strategy and some existing DTC methods are conducted on a 0.55-kW IM platform. The proposed DTC method has proven to achieve better steady-state performance, while retaining fast dynamic response of TDTC. Furthermore, the proposed method can obtain almost constant average switching frequency in the entire speed range, especially with rated load, due to the utilization of proportional-integral type torque regulator. [ABSTRACT FROM AUTHOR]

In this article, we present a dual-stator structure-parallel fault-tolerant machine (DSSPFTM). In this machine, the radial-flux dual-stator structure with a higher density is adopted to the fault-tolerant system. For better performance in fault condition, the combination of permanent-magnet component (PMC) and reluctance component (RC) in the rotor and large-opening slot is proposed. Because of the same poles and torque-variation principle, the PMC and RC are combined. The PMC is devised to supply most of the torque in normal conditions, while the RC provides enough self-inductance for limiting current under short-circuit (SC) occasion. Most of the flux leakage is separated from the active flux and the overload ability is improved. The design process of DSSPFTM is described in steps and details. Based on the fundamental of maximum torque under normal conditions, PMC and RC are integrated together. The end flux leakage originating from the adjacency of RC to PMC and the effect of RC length on torque are analyzed. The back-EMF, torque, inductance, loss, efficiency, and SC analysis are demonstrated. The stress and deformation distribution of the rotor and the comparison with the traditional structure are conducted. A prototype DSSPFTM is designed and manufactured. The experiments accord with simulations, indicating that the DSSPFTM with fault tolerance can improve the torque density effectively. [ABSTRACT FROM AUTHOR]

This paper presents an integrated control strategy for a starter/generator (S/G) system based on five-phase dual-stator winding induction machine (FPDWIM). The FPDWIM has a cage-type rotor and two sets of stator windings. One is a five-phase control winding (CW), and the other is a five-phase power winding (PW). In the starting mode, the FPDWIM works as a motor. The CW provides both active power and reactive power to drive the engine. In the generating mode, the CW mainly handles reactive power while the PW outputs active power. To achieve the integration of the starting and generating controls, indirect CW-flux-oriented control (ICWFOC) to operate in both starting and generating modes is proposed in this paper. In starting mode, the CW current and flux are controlled to output a constant starting torque; while in the generating mode, both CW and PW dc bus voltages are regulated. In this way, the principles and structures of the control strategies in both modes are compatible, resulting in a simpler implementation and improved performance. With the proposed control strategy, the system can complete the starting–generating operation with a smoother transition process. Simulation and experimental results are compared to validate the proposed control strategy. [ABSTRACT FROM AUTHOR]

Dual stator-winding induction generator (DWIG) is attractive in stand-alone power systems, and the aim of this paper is to develop the dc generating system of five-phase DWIG with an open phase. First, the relationship between flux and torque is constructed based on the reduced-order transformation, modified flux, and current. Second, the relation between modified voltage and current on the dq plane is constructed. The current of fundamental plane is used for the control loop of the power-winding voltage and control-winding voltage, respectively. Third, the current of the modified secondary subspace plane is used to control the five-phase DWIG operation at minimum control-winding loss. Finally, the simulation and experimental results are given to verify that the amplitude of phase current and output voltage can be regulated effectively by the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this paper, a new electric drive system based on a six-phase ten-pole dual-winding fault-tolerant permanent-magnet (DFPM) motor for aerospace applications is proposed and investigated. The proposed DFPM motor consists of optimal surface-mounted permanent-magnet (PM) rotor and 12-slot stator with two sets of independent three-phase concentrated armature windings on alternate teeth, which incorporates the merits of high power density and high efficiency of the PM motor and high fault tolerance of the dual-winding motor. To achieve the fault-tolerant performance of the electric drive system, the redundant fault-tolerant control strategy based on the failure diagnosis and redundancy communication is proposed and applied to the electric drive system. Then, the operational performance of the drive system under open-circuit and short-circuit fault has been verified by simulation and experiments. The research results show that the open-circuit and short-circuit fault can be detected immediately and the output performance of the DFPM motor under fault conditions is almost the same as the normal condition, which verified the proposed electric drive system, DFPM motor, and fault-tolerant control strategy. [ABSTRACT FROM PUBLISHER]