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Axial Flux Permanent Magnet (AFPM) machines with ironless rotors are an attractive and recently studied solution in low-speed applications, due to their potentially high power/weight ratio, high aspect ratio, and high efficiency. Nevertheless, these machines are prone to be affected by manufacturing tolerance during its fabrication process and consequently, the magnets may move freely inside the rotor structure. This work presents a statistical analysis of manufacturing tolerances of an AFPM machine with an ironless rotor, considering several magnet fault types. A computationally efficient superposition method is developed and implemented to obtain both the cogging torque and rated torque considering several tolerance combinations with acceptable accuracy. The results obtained from a statistical analysis of 10,000 designs of a two-stator one rotor tooth coil winding AFPM (TCW-AFPM) machine allowed us to identify the parameters with the most impact on relevant performance indicators and disclosed a substantial increase in cogging and ripple torque when unavoidable combined tolerances are present. [ABSTRACT FROM AUTHOR]

In this paper, a discrete skew methodology is presented to understand the effect of skewing angle on electromagnetic torque in SynRM design. A new approach is proposed to estimate the amplitude of each torque ripple component as a function of skewing angle. The reduction factor for each harmonic component is derived in general form, allowing for the determination of overall torque ripple waveform. The validity of the proposed method is evaluated through the examination of two SynRMs, resulting in a torque ripple reduction of up to 70%. The results obtained through the use of a proposed analytical ripple reduction estimator and FEA evaluation showed good agreement. The proposed skewing technique was applied on a previously optimized triple-barrier SynRM with a positive outcome: a consistent torque ripple reduction tackling relevant harmonic components. The analysis of harmonic distribution of torque ripple is mandatory for the selection of the optimal skewing strategy when following the proposed method, with two-step skewing recommended for mostly-purely-sinusoidal torque waveforms, and multi-step skewing recommended for machines with multiple higher-magnitude harmonic components. [ABSTRACT FROM AUTHOR]

This article proposes a simple method to calculate a current vector trajectory for the enhanced operation of the electric power generation system based on a synchronous reluctance machine (SynRM). Owing to magnetic saturation and cross magnetization, the performance and the torque capability of a SynRM vary according to the position and the value of the stator current. State-of-the-art control methods usually assume parameters with constant values, especially the inductance, neglecting saturation, leading to possible uncertainty in the machine operation. Therefore, a current vector trajectory to operate this type of machine, as a generator, in an extended speed range, with enhanced performance and considering magnetic saturation is proposed. A straightforward algorithm based on the inductance characteristic of the machine is used to calculate the trajectory of the stator current vector. This trajectory is evaluated via the numerical simulation of an experimentally validated finite-element model of a SynRM. The results show that the proposed current vector trajectory can improve the torque capability to 5% concerning the estimated trajectory without considering saturation. Experimental results are also provided to demonstrate the enhanced operation of the generator. [ABSTRACT FROM AUTHOR]

This article presents an accurate analytical model (AM) for synchronous reluctance machine (SynRM) that incorporates the effect of stator slots on the air gap flux density and torque waveforms. From the formulation of magnetic potential in the air gap for both the stator and rotor, the flux density is obtained, considering the first harmonic of the flux density and the electric loading, the average torque is calculated using the Lorentz’s force. The ripple torque is obtained from the energy stored in magnetic circuit. The method is developed for a rotor with one flux barrier per pole and then extended to a larger number of barriers. To validate the results obtained by the AM proposed finite element analysis have been carried out. Several comparisons have been derived considering different rotor positions as well as different harmonic orders, and the pros and cons of the method are highlighted. The model performs fast and can predict results with high accuracy, and can be adopted to speed up the preliminary design and optimizations of this type of motors, with respect to finite element. In addition, from the analytical expressions it is possible to obtain all the correlations between electrical, magnetic, and geometrical characteristics of the machine, with the advantage of enabling a faster machine design. [ABSTRACT FROM AUTHOR]

Traction motor design significantly differs from industrial machine design. The starting point is the load cycle instead of the steady-state rated operation point. The speed of the motor varies from zero to very high speeds. At low speeds, heavy overloading is used for starting, and the field-weakening region also plays an important role. Finding a suitable field-weakening point is one of the important design targets. At the lowest speeds, a high torque output is desired, and all current reserves of the supplying converter unit are used to achieve the torque. In this paper, a 110-kW 2.5-p.u. starting torque and a maximum 2.5-p.u. speed permanent-magnet traction motor will be studied. The field-weakening point is altered by varying the number of winding turns of machine. One design is selected for prototyping. Theoretical results are verified by measurements. [ABSTRACT FROM PUBLISHER]

Hybrid and full electric technologies are fast emerging in vehicles and mobile working machines, where electric machines and internal combustion engines are used together to power the systems. Permanent magnet (PM) technology plays an important role here despite the high magnet prices. This paper theoretically and empirically studies the design principles of PM synchronous machines (PMSMs) for hybrid applications, where a high starting torque and a wide field weakening range are needed. Several embedded-magnet PMSM magnetic circuit topologies are considered as possible candidates. A 10-kW PMSM prototype was built and tested. Experimental results verify the theoretical considerations well. [ABSTRACT FROM PUBLISHER]

High power machine has become a large market for wind power and ship propulsion electric, among other applications. Since the size of these machines is much larger than conventional industrial ones, optimum design must be considered in order to reduce the material cost and increase profitability. In this paper, a simple analytic optimization algorithm is used to maximize the apparent airgap power transferred under tangential stress constraint. In this approach, close related expressions between the main design variables, operational restrictions, and external dimensions are derived to build the mathematical structure of the optimization process. To improve the torque capacity estimation of the designed machine, a correction procedure, based on the previous result, is used to remove the idealizations considered for the initial design. Close agreement with the finite element analysis results are found with this approach, which is based on analytical method. [ABSTRACT FROM AUTHOR]

In designing new topologies for permanent-magnet machines based on rare earth magnets, it is necessary to diminish the undesired cogging torque. This paper presents a 3-D finite-element analysis to evaluate the effect of magnet shape and stator displacement on cogging torque reduction, for axial flux machines. It analyzes the final electromagnetic torque for the proposed configurations. Finally, it presents the resultant cogging torque waveform for a 5.0 kW prototype, based on our optimization techniques. [ABSTRACT FROM AUTHOR]

Cogging torque is a source of vibration and noise in permanent-magnet (PM) machines. This torque is proportional to the PM flux and the reluctance variation, and is independent of the load current. In this paper, two methods for cogging torque reduction in an axial PM machine with field weakening capability are presented. The machine's rotor configuration considers two sections: one PM pole that provides the field excitation and one iron section in charge of providing low d-axis reluctance. Significant reduction of the cogging effects is achieved by adjusting stator geometry and rotor pole configuration. Three-dimensional finite-element analysis is used to demonstrate these improvements. Conclusions and design recommendations are presented for a 5-kW eight-pole PM machine prototype under construction. [ABSTRACT FROM AUTHOR]

This paper analyzes the impact of manufacturing tolerances on the cogging torque of a 24-slot 28-pole tooth-coil-winding permanent magnet synchronous machine with a modular stator core (TCW-MPMSM). Dimensional tolerances and asymmetries associated with the modular topology are studied by means of finite element simulations in order to identify key parameters that increase the cogging torque above the expected values of a faultless machine. Among five selected dimensional parameters, it was found that angular displacement, radial displacement, and tooth–tip width deviations of the stator segments have the most significant impact on the cogging torque. Considering these three key parameters, a full-range tolerance analysis is carried out by means of a proposed superposition-based approach, evaluating all possible combinations of typical deviation values. It is concluded that the cogging torque increment, generated by tolerances, is relatively independent of the faultless tooth–tip width of the stator segments and the arc-to-pole ratio. Robustness of the TCW-MPMSM, regarding cogging torque generation, depends on both the tightness of the tolerances handled in the manufacturing process and the rated cogging torque: the lower the cogging torque of the ideal machine, the less robust is the machine and, therefore, manufacturing imperfections will be required to be tightened. [ABSTRACT FROM AUTHOR]