Eccentricity is an inevitable fault in electric motors and hence its diagnosis is an important topic. Thus, the influence of static and dynamic eccentricities on the harmonics of the frequency spectra of the unbalanced magnetic pull is analyzed. In this article, dimensional tolerances of the rotor and the stator are also considered. All parts have dimensional tolerances in their designs and their real magnitudes vary to some extent from the theoretical values after the manufacturing process. Thanks to analytical calculations and finite element simulations, verified with experimental results, it is observed that the deviations originated by the manufacturing tolerances produce changes in the amplitudes of some harmonics and also additional and characteristic harmonics in the frequency spectra of the unbalanced magnetic pull. These are not negligible and must be taken into account when robust eccentricity detection procedures are defined. Otherwise, harmonics originated by tolerances and by eccentricities can be misidentified. Finally, after decoupling the effect of tolerances and eccentricities, the frequency harmonics that are indicators of rotor tolerances are determined, and a new methodology based on ratios of amplitudes of adjacent harmonics is proposed to identify eccentricities.

Linear switched-flux machines are a kind of permanent magnet machine with a passive ferromagnetic secondary. Therefore, they can achieve both a good performance and a low cost in long stroke applications. However, due to the end effect, these machines generate high detent force and on load thrust force ripples. There are several solutions in the literature that aim to minimise the thrust ripple. One of those solutions is the placement of additional poles in the ends of the machine. These can be passive, i. e. simple ferromagnetic teeth, or active, with additional magnets. The former is the most common solution in the literature. In this article, the optimal configuration of the additional poles is discussed via 4 additional pole sizing strategies, and the influence of the design variables and optimisation objectives is analysed. Then, a generic additional pole configuration is proposed, which combines a high effectiveness and a simple design. Finally, an experimental validation is carried out, and the measurements confirm the results from the optimisation.

Nowadays the comfort in passenger transport system is very relevant. One source of noise and vibration is the torque ripple. Torque ripple can be generated by an inappropriate machine control tuning and by the inherent torque ripple of the machine. In permanent magnet machines, the inherent torque ripple is composed by three components: electromagnetic torque, reluctant torque, caused by the winding magnetic field, and reluctant torque caused by the permanent magnet magnetic field, commonly known as cogging torque. In order to assess the torque ripple at each working point, the electromagnetic analysis using a Finite Element Method (FEM) is a very accurate solution. In a dynamic simulation the high computational load is the main drawback of the FEM analysis. To overcome this problem, in this paper the use of a mixed approach is proposed, in which the parameters of a dynamic vector model are previously adjusted using FEM characterization. The aim of this strategy is to do just one complex FEM simulation, so later a quicker dynamic model can be used. In this article, an adjusted dynamic vector model of a Permanent Magnet Synchronous Machine (PMSM) is presented. The inputs of the model are the phase voltages and the rotor position. The outputs are the currents, the flux linkages and the total electromagnetic torque, including all the parasitic components of the torque ripple. The advantages of this model are the reduction of simulation time and the possibility to integrate it in a more general dynamic simulation platform.

Permanent Magnet Synchronous Motors (PMSMs) are increasingly being used and are required to satisfy noise and vibration specifications. Thus, it is necessary to develop design guidelines for electric motors that consider vibration response as a key output of the design. This work shows the influence of the main design parameters regarding PMSMs: the number of slots and the number of poles. First, the influence of the number of slots in the natural frequencies is analysed by Finite Element calculations, which are experimentally verified. Then, the analytical calculation of the vibration response is explained. This is applied for several combinations of the number of slots and the number of poles, and the results are compared. Considering the analytical development, a procedure to choose the most adequate combination of the number of slots and poles is proposed. The analytical predictions are validated according to experimental measurements in two machines.

Nowadays the compactness, cost effectiveness and low torque ripple are some of the most demanded requirements in electrical machines. Due to these requirements, Fractional Slot Concentrated Windings Permanent Magnet Synchronous Machines are getting more and more popularity. However, this kind of machines are sensible to mass production tolerances, which can increase the ideal low torque ripple. Apart from that, decreasing the volume of magnets and/or selecting magnets with worse thermal properties, the production costs are decreased. Nevertheless, this fact increases the demagnetization risk. Therefore, it is important to take into account the effects of the demagnetization on the torque ripple. This work investigates the demagnetization effects on the torque ripple assuming mass production tolerances by Finite Element Method and with experimental results.

The use of electric motors, and particularly, Permanent Magnet Synchronous Motors, is increasing in recent years, and their vibration response is one of the most crucial aspects regarding their behaviour. Thus, the reduction in vibrations is one of the key objectives when optimizing electric motors. In an initial design state, the influence of the main design parameters on the behaviour of the machines is not always clear. For that reason, this work presents a global sensitivity analysis procedure that allows identifying the most influential design parameters and determining guidelines to optimize the design of Permanent Magnet Synchronous Motors. First, the analytical calculations employed to estimate the electromagnetic torque and the vibration response of the machine are described. Then, the sensitivity analysis procedure, based on the Monte Carlo method, is presented, and the conditions to apply the method successfully and accurately are analysed. Finally, the sensitivity analysis is performed for a particular electric motor design, and some general design guidelines are deduced, which can be extrapolated to similar machines.