Low speed, high torque machines are used in wind turbines where the turbine rotor is directly connected to the generator. A permanent magnet synchronous generator using high-energy rare-earth ...permanent magnets (PMs) is one common choice for this application, but rare-earth PMs have supply insecurities and cost risks. A rare-earth free 32-pole PM generator, using ferrite PMs in a spoke-type rotor, for use in a 12 kW experimental wind turbine is built and tested. Voltages and currents at load and no load are measured, as well as the magnetic field in the end regions of the machine. The generator can deliver the required power at nominal speed and has low harmonic content in the output. The electrical measurements are compared to two-dimensional finite element design calculations and the experimental results are lower than expected from simulations. The measured voltage is lower than expected, requiring a higher current than calculated for the rated power. Three-dimensional magnetic field simulations show that there are leakage flux paths in the end-regions that the two-dimensional design calculations overlook, explaining the discrepancy between simulations and measurements.
This article proposes a robust optimization method for hybrid permanent magnet (HPM) machines, aiming to eliminate the influence of permanent magnets (PMs) asymmetric uncertainties. Exemplified by a ...12-slots/10-poles (12s10p) HPM machine, the optimization method is specifically clarified. First, uncertainties of two types of PMs are comprehensively analyzed and the worst combination of these uncertainties are estimated. Then, the design of experiments (DOEs) technique is utilized to take samples, and the corresponding performance of samples with and without consideration about uncertainties are simulated by finite element analysis (FEA), respectively. After that, a dual-level kriging surrogate model is constructed. And the difference of the two levels, as a quantitative index of robustness, is added as an additional optimization objective. Finally, a multi-objective optimization algorithm non-dominated sorting genetic algorithm (NSGA-II) is carried out. The optimization results indicate that the proposed method can effectively reduce the additional torque tipple brought from asymmetric uncertainties of PMs. In addition, a prototype is manufactured and tested to further verify the method.
This paper proposes a novel permanent magnet vernier synchronous machine with saddle shaped permanent magnets. The torque of permanent magnet vernier synchronous machine with saddle shaped permanent ...magnets is increased of 35.4% and 45.6% compared with the permanent magnet vernier synchronous machine with V shaped permanent magnets and tile shaped permanent magnets respectively. The torque ripple of permanent magnet vernier synchronous machine with saddle shaped permanent magnets is reduced by 0.1% and 1.7% compared with the permanent magnet vernier synchronous machine with V shaped permanent magnets and tile shaped permanent magnets respectively. To facilitate the analysis, the saddle shaped permanent magnets are equivalently transformed to fan shaped permanent magnets, which is ensure that the pole arc angles and air-gap magnetic flux are unchanged. The rotor flux saturation region is modeled to improve the analytical calculation accuracy. The Laplace and Poisson equations are established for each part of the machine, the general solutions of the respective parts are solved, and the boundary conditions and intersection conditions are utilized to solve the factors. Compared with the finite-element method results, the torque difference is 0.32 N ∙ m and the torque ripple difference is 0.2%. The correctness of the analytical calculation is verified by comparing with the finite-element method results. The auxiliary slot angle and slot depth can be optimized resulting in a higher torque and lower torque ripple.
Biased magnetic flux produced by a permanent magnet can reduce the power consumption of the suspension system in bearingless motors or magnetic bearings. However, the ability to generate suspension ...biased magnetic flux with a single permanent magnet tends to be saturated with the increase of the magnetising width. In order to solve the above problem, an axially superposed permanent magnet biased bearingless motor, which consists of a 12/8 reluctance motor for producing torque and two permanent magnets for producing desired biased magnetic flux density is present. The structure and working principle are introduced, and the electromagnetic characteristics are analysed by finite element analysis. The results verify that the proposed bearingless motor has the excellent merits of weak coupling between the torque system and suspension force and satisfactory suspension performance. Furthermore, much more biased permanent magnets could also be used for the suspension system of ultra-high speed, high power and slender bearingless motors such as flywheel energy storage systems.
Variable flux permanent magnet synchronous machines (VF-PMSMs) in which the magnetization state of low coercive force permanent magnets can be actively controlled to reduce losses in applications ...that require wide-speed operation have been proposed recently. While prior focus has been on achieving magnetization state manipulation without oversizing the inverter and obtaining higher torque capability, this paper extends the design objectives to include the power requirements of an electric vehicle traction motor over its entire speed range. Finite-element methods are used to study the effect of combinations of low coercive-force and high coercive-force permanent magnets arranged in either series or parallel on the performance of VF-PMSMs. While both configurations help improve the torque density, only the series configuration can help improve the high speed power capability. Experimental results showing the variable magnetization state property, torque-speed capability, and loss reduction capability of a series magnet configuration VF-PMSM test machine are presented.
Replacement of Dy and substitution of Nd in NdFeB‐based permanent magnets by Ce, the most abundant and lowest cost rare earth element, is important because Dy and Nd are costly and critical rare ...earth elements. The Ce, Co co‐doped alloys have excellent high‐temperature magnetic properties with an intrinsic coercivity being the highest known for T ≥ 453 K.
This study presents an optimisation method for slotless permanent magnet synchronous machines to maximise torque density. The slotless structure with outer rotor and Halbach array has been selected ...to limit iron losses, torque ripple, cogging torque, and high-order harmonics. High-speed operation compounds both ac copper loss and mechanical stress. The former causes a temperature rise in the machine, while the latter is induced by strong centrifugal forces. A finite-element analysis-based optimisation method that utilises a parallel multistart, mesh adaptive direct search strategy is proposed to consider ac copper loss and mechanical stress as constraint variables. Finally, the torque densities of titanium and aermet shell designs were compared to show how material selection provides a trade-off in terms of torque production, mechanical stress, and weight.
This paper proposes a novel high-speed axial flux permanent magnet synchronous motor (AFPMSM) with hybrid permanent magnets (PMs) to reduce the magnet cost. Based on basic AFPMSM with sinusoidal ...NdFeB PMs, the proposed model is designed with an equal quantity of ferrite and NdFeB PMs, wherein the hybrid PMs are divided into parallel and vertical to the magnetization direction of the PM. Furthermore, three kinds of hybrid PM arrangements are adopted for the AFPMSM and the relative analysis of the magnetic circuits is carried out. Then the no-load, load electromagnetic performance and torque cost of the AFPMSMs with three PM arrangements are simulated and compared by the finite element method (FEM). Finally, the demagnetization and stress analysis are performed to verify the stability of the AFPMSM with hybrid PM arrangements.
This article presents a delay-suppressed sliding-mode observer (SMO) to observe the real-time rotor position of a permanent magnet synchronous machine (PMSM) controlled by vector control algorithms. ...First, in order to solve the low-pass filter (LPF) delay problem existing in the traditional signum function-based SMO, a brand new hyperbolic function is initially selected as the switching function. Because a hyperbolic function with a proper boundary layer is capable of reducing the chattering phenomenon of an SMO, it is not necessary to reemploy LPFs to eliminate the adverse impacts of chattering on the position estimation accuracy. In order to ensure the reachability and stability of the hyperbolic-function-based SMO, the observer gain is calculated by the means of a Lyapunov function in this article. Second, to solve the problem of calculation delay caused by digital computation, a current precompensation scheme based on dual-sampling strategy in one switching period is proposed. After compensating the calculation delay, the accuracy of position estimation as well as the motor control performance can be improved. Finally, the proposed SMOs with and without delay compensation are verified by both simulation and experiments that are conducted on a three-phase 1.5-kW PMSM drive prototype.
Permanent magnets (PMs) have been widely used in different types of electrical machines to improve their performance. This article introduces a novel multi-tooth hybrid-excited switched reluctance ...motor (MT-HESRM) with PMs placed between the end teeth of the adjacent modules. Thanks to the innovative method of embedding PMs, a unique design is developed. First, the operating principle of the motor is explained, and the magnetic circuit model of the motor is analyzed. The magnetic characteristics in terms of flux density, flux linkage, inductance, and torque are obtained and compared with those of its PM-less counterpart. The mathematical model of the reluctance and PM torques is presented. The reluctance and PM torques are decoupled using the finite-element analysis, and the torque contribution of the PMs is discussed. The steady-state operations of both motors with both current chopping and single-pulse controls are analyzed and compared under different speeds. Finally, both motors are manufactured, the laboratory tests are done, and the experimental results are extracted. Both the simulation and test results elucidate that the MT-HESRM, which has only three small PMs as auxiliary flux sources, has unique features in terms of high output power and torque with a negligible cogging torque.
PDF
