Losses created by skin and proximity effects can be significant in medium to high-speed ac machine designs. These have been extensively studied for form wound coil machines, but regarding randomly-placed round-wire windings, bundle-level proximity losses have been either neglected, computed via finite element (FE) simulations or estimated analytically by methods that require to know the location of each strand within the slot. This article presents a practical, yet accurate method to estimate bundle-level proximity losses in random-wound ac machines without having to specify the location of each individual conductor. The method consists on approximating the turn size and the arrangement of the conductors within the slot from the overall dimensions of the slot and the winding via simple expressions. This procedure is successfully validated via FE simulations and by constructing and experimentally testing two Interior Permanent Magnet Synchronous Machine prototypes with different winding characteristics.

This paper proposes a combined electromagnetic and mechanical topology optimization for weight reduction in electrical machines based on Finite Element Analysis (FEA) and Evolutionary Structural Optimization (ESO). The devised method is an on- off-type algorithm with adaptative mesh in which low flux density and low Von Mises stress cells are removed successively from a first machine design. With this approach, the weight of the machine can be considerably reduced without compromising the electromagnetic performance of the machine, with a reduced computation time compared to other topology optimization methods. A case study involving a 1.2 MW low-speed, permanent magnet motor is analyzed under different conditions (algorithm parameters, initial mesh, rotational speed) and used to compare the proposed method with two other topology optimization approaches.

In this article, the compression characterization of silicon-based magnetorheological elastomers is addressed, emphasizing the difficulties associated to the test set-up in order to obtain accurate results of the behaviour of the material. Measurement errors associated to friction and vibration coupling due to design flaws in the electromagnet are solved by providing guidelines on an adequate electromagnet layout. The designed electromagnet allows conducting compression dynamic tests up to 300 Hz in specimens of dimensions 40 x 40 x 8 mm(3), reaching magnetic flux densities in the order of 1000 mT and showing the expected increase in the dynamic stiffness. Additionally, the electromagnet might be used in the manufacturing and curing of anisotropic magnetorheological compression specimens.

In the last few years, the reduction of the dependency on rare-earth magnets has been one of the main concerns for electrical machine manufacturers. Synchronous reluctance machines (SynRMs) and ferrite permanent magnet-assisted synchronous reluctance machines (PMa-SynRMs) are emerging as alternatives to permanent magnet synchronous machines (PMSMs) in several applications. In low-speed high-torque applications, PMSMs with large amounts of rare-earth magnets are commonly employed. Thus, it is of particular interest to replace PMSMs by SynRMs or PMa-SynRMs. This article studies the feasibility of using SynRMs and ferrite PMa-SynRMs for a direct-drive elevator system. The challenge lies in obtaining performance characteristics comparable to those of PMSMs, but without resorting to the use of rare-earth permanent magnets. The main criteria for designing SynRMs and PMa-SynRMs for low-speed high-torque applications are presented. Afterwards, a SynRM and a ferrite PMa-SynRM are designed for 160 rpm 200 Nm rated conditions, and a performance and cost comparison between these machines and a commercial PMSM is conducted.

Interior Permanent Magnet Synchronous Machine (IPMSM) are high torque density machines that usually work under heavy load conditions, becoming magnetically saturated. To obtain properly their performance, this paper presents a node mapping criterion that ensure accurate results when calculating the performance of a highly saturated IPMSM via a novel magnetic reluctance network approach. For this purpose, a Magnetic Circuit Model (MCM) with variable discretization levels for the different geometrical domains is developed. The proposed MCM caters to V-shaped IPMSMs with variable magnet depth and angle between magnets. Its structure allows static and dynamic time stepping simulations to be performed by taking into account complex phenomena such as magnetic saturation, cross-coupling saturation effect and stator slotting effect. The results of the proposed model are compared to those obtained by Finite Element Method (FEM) for a number of IPMSMs obtaining excellent results. Finally, its accuracy is validated comparing the calculated performance with experimental results on a real prototype.

This paper studies the feasibility of using synchronous reluctance machines (SynRM) for low speed-high torque applications. The challenge lies in obtaining low torque ripple values, high power factor, and, especially, high torque density values, comparable to those of permanent magnet synchronous machines (PMSMs), but without resorting to use permanent magnets. A design and calculation procedure based on multistatic finite element analysis is developed and experimentally validated via a 200 Nm, 160 rpm prototype SynRM. After that, machine designs with different rotor pole and stator slot number combinations are studied, together with different winding types: integral-slot distributed-windings (ISDW), fractional-slot distributed-windings (FSDW) and fractional-slot concentrated-windings (FSCW). Some design criteria for low-speed SynRM are drawn from the results of the study. Finally, a performance comparison between a PMSM and a SynRM is performed for the same application and the conclusions of the study are summarized.

A computational fluid dynamics (CFD) model representing the effect of wafters in a totally enclosed electric machine is presented, introducing the most relevant theoretical assumptions and simplifications. The validation of the model is conducted through experimental measurements. From the CFD simulation data, a second-order response surface is developed using statistical tools, from which the wafters' influence on the convective heat transfer from the stator end windings is predicted. Wafter design criteria are obtained from the response surface information. Finally, a specific case is analysed, showing through CFD simulations that temperatures in the machine are reduced by including wafters in the design.