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This paper presents a detailed analysis of the electromagnetic force and vibration behavior of an axial flux permanent magnet synchronous machine (AFPMSM). First, the AFPMSM configuration and two types of dual three-phase winding are introduced. Subsequently, the electromagnetic force of the double-stator inner-rotor AFPMSM is investigated. Its spatial and temporal characteristics are derived analytically and validated through two-dimensional Fourier decomposition. A multiphysics model is established to calculate the vibration of the AFPMSM, which includes control, electromagnetic, structural, and vibration model. The accuracy of this multiphysics model is verified by the modal and vibration test. Furthermore, the vibration of the AFPMSM with three winding types considering current harmonics are calculated based on the multiphysics model. The vibration performance of the AFPMSM with three different winding types are compared and the mechanism of vibration is discussed. It was concluded that the novel detached winding could mitigate the vibration of dual three-phase AFPMSMs. Finally, the vibration test is carried out to validate the theoretical analysis and the experimental results agree well-with the simulation results. This paper provides an effective method for double-stator permanent magnet synchronous machine (PMSMs) to reduce vibration. [ABSTRACT FROM AUTHOR]

Multiphase machines are famous for their fault-tolerant capability. Conventional fault-tolerant model predictive current control (FT-CMPC) of multiphase machines suffers from high computational burden, low switching frequency, and relatively high current harmonics. This paper proposes a fault-tolerant PWM predictive control (FT-PWMPC) to enhance the performance of fault-tolerant predictive control strategy without using complex enumeration method. The reference phase voltages are generated by a postfault mathematical model in stationary reference frame and transformed to duty cycles with a properly set common-mode voltage. Then, a comparative study of fault-tolerant predictive control strategies is presented, including FT-CMPC, FT-two-vector-based-predictive control, and the proposed FT-PWMPC. The control strategies are implemented with the same sampling frequency or switching frequency on a six-phase permanent magnet synchronous machine test bench. Experimental results of dynamic response, steady-state currents, vibration, and parameter sensitivities are given to identify the advantages and limitations of each control strategy. [ABSTRACT FROM AUTHOR]

This paper investigates the postfault operation of a novel six-phase double-stator axial-flux permanent-magnet machine with detached winding connection. In previous research, this configuration was found to be superior to existing winding connection except that its unbalanced magnetic force in the postfault operation cannot be ignored. In this paper, an axial magnetic force balancing method (AMFBM) is proposed to reduce unbalanced magnetic force by deducing a set of special winding current. By comparing electromagnetic torque and axial magnetic force of the traditional winding current and the proposed method in postfault operations through a finite-element analysis, it is verified that AMFBM can reduce most of the unbalanced axial magnetic force as well as keeping torque ripple at a low level. In order to realize the AMFBM, finite control set model predictive control is adopted. A postfault model of dual-three-phase permanent-magnet machines with modified vector space decomposition method is first brought forward to predict the future behavior of the controlled variables with various voltage inputs. After that, a cost function is designed to track the desired winding current by evaluating all the predictions to decide the next step of the inverter. Experimental results show that the control scheme performs well in both dynamic and steady-state situations. [ABSTRACT FROM PUBLISHER]

Recently, stator dc current excited vernier reluctance machines (dc-VRMs) which have concentrated field and armature windings in stator, are gaining more and more research interest due to their features of robustness rotor structure, low cost, and easy heat dissipation. This paper proposes a novel field winding connection for dc-VRMs. Taking the stator/rotor slots of 12/10 machine as an example, the electromagnetic performance including back electromotive force (EMF), pulsating torque, and capability are analyzed using the theoretical and finite element analysis. The results show that compared with the previous machine having the same stator/rotor slots, machine with the proposed field winding connections exhibits a doubling back EMF, and 60% higher torque density. [ABSTRACT FROM AUTHOR]

This paper proposes a novel detached winding configuration for asymmetric six-phase double-stator axial flux permanent magnet machines aiming at fault-tolerant applications. Due to the machine unique double-stator structure, the six-phase winding can be separated into two three-phase windings with 30 electrical degree angle shift and arranged in different stators, which is the basic idea of the detached winding. In this paper, the connection of detached six-phase winding is first given, followed by a comprehensive comparison of the conventional six-phase winding and the detached winding in aspect such as the winding factor, electromotive force, inductances, rotor eddy current loss, and torque in normal condition. Performance under fault-tolerant operation is investigated by the copper loss minimization control strategy. The results show that by applying the detached winding instead of the conventional winding, rotor eddy current losses could be reduced by 25% and 70% under normal and fault-tolerant operation, respectively, without sacrificing torque output. This implies that under fault operation, the excess heating in rotor could be reduced and the machine durability can be enhanced. A prototype machine is built to validate the performance of the detached winding design. The experimental results match well with simulation analysis. [ABSTRACT FROM AUTHOR]

Stator dc field winding excited vernier reluctance machines are increasingly attracting research interest recently due to their low cost and highly reliable rotor structure. In this paper, the design of these machines is studied systematically using both theoretical equations and finite element analysis (FEA). First, the general structures of these machines and their operation principles are discussed. Second, based on the operation principle, the back electromotive force, torque, and power factor expressions are deduced in terms of the geometrical variables. Several key design parameters are defined, including stator/rotor slot/pole combinations, air gap, split ratio, field/armature coil turn ratio, and stator/rotor tooth arc combination. Third, the deduced theoretical expressions are verified by the FEA. Finally, a prototype is designed and tested to verify the analysis results. [ABSTRACT FROM PUBLISHER]