This paper deals with fractional-slot multilayer windings. They are becoming attractive since they allow reducing the harmonic content of the magnetomotive force. Some examples of such a type of ...windings are reported in the literature, but they are limited to a few slot/pole combinations. On the contrary, in this paper, a general theory is presented. The main rules for the design of multilayer windings are illustrated. It is also investigated if the adoption of a multilayer winding makes possible the limitation of the torque ripple and the rotor losses of the machine. Several examples and experimental tests are reported to investigate the advantages and the convenience of adopting multilayer windings.
The focus of this paper is the potential electrification of specialized agricultural tractors involved in vineyards and orchards. This category of machinery has not received research attention to ...date; however, regulations are encouraging lower emissions and higher efficiency, requiring the adoption of new technologies. Traction makes up only a limited part of this application, and the working cycle is not trivial; therefore, the design of the system is not straightforward. This study takes advantage of experimental measurements carried out under real operating conditions on a traditional specialized tractor, which was chosen as performance target. The performance requirements of the hybrid powertrain components are investigated, with particular focus placed on the electric motor. According to the dimension constraints, the design of the electric motor is carried out considering the requirements in terms of its thermal-equivalent torque and overload capability. The results are validated through a detailed thermal simulation under real duty cycles.
Despite a strong nonlinear behavior and a complex design, the interior permanent-magnet (IPM) machine is proposed as a good candidate among the PM machines owing to its interesting peculiarities, ...i.e., higher torque in flux-weakening operation, higher fault tolerance, and ability to adopt low-cost PMs. A second trend in designing PM machines concerns the adoption of fractional-slot (FS) nonoverlapped coil windings, which reduce the end winding length and consequently the Joule losses and the cost. Therefore, the adoption of an IPM machine with an FS winding aims to combine both advantages: high torque and efficiency in a wide operating region. However, the combination of an anisotropic rotor and an FS winding stator causes some problems. The interaction between the magnetomotive force harmonics due to the stator current and the rotor anisotropy causes a very high torque ripple. This paper illustrates a procedure in designing an IPM motor with the FS winding exhibiting a low torque ripple. The design strategy is based on two consecutive steps: at first, the winding is optimized by taking a multilayer structure, and then, the rotor geometry is optimized by adopting a nonsymmetric structure. As an example, a 12-slot 10-pole IPM machine is considered, achieving a torque ripple lower than 1.5% at full load.
Today, agriculture industry has a significant impact in global greenhouse gas emissions. A large amount of pollutants come from diesel internal combustion engines, widely used in agricultural ...machinery. Since mechanization in agriculture is fundamental to achieve a proper food production for a growing human population, changes are needed in common agriculture engineering thinking in order to develop new farming machinery that could outperform conventional ones in terms of environmental impact, as well as performance, productivity and safety. Electrification is a feasible solution. A comprehensive review about agricultural machinery electrification is reported in this paper, with a particular focus on hybrid electric tractors and their implements. The introduction of electric drives in farming tractors is discussed in detail by looking at the main findings in literature and considering state-of-the-art technology. Proposals and prototypes from manufacturers are covered too, as well as economic assessments and future trends.
This paper deals with the electromagnetic characterization of a laminated toroidal ferromagnetic core made through additive manufacturing, specifically using the laser powder bed fusion process. The ...continuing demand for increasingly efficient, lightweight, and higher performance electric machines is creating huge challenges in the design and realization of new electric motor solutions. The constant improvements in additive manufacturing technologies have prompted researchers to investigate the possibility of adopting these production techniques for the manufacture of high-value electric motors. For these reasons, this paper investigates the ferromagnetic characteristics of an additively manufactured core made with FeSi6.5 powder. The BH curve and the specific iron losses of the processed material have been measured so that they can be compared with a commercial lamination, and have the possibility of carrying out more precise finite element simulations.
This paper focuses on the selection of a fractional-slot winding for permanent-magnet (PM) machines. The choice of the proper combination of the number of slots and number of poles, together with the ...corresponding winding layout, has a strong impact on the PM machine performance, in terms of torque density, torque ripple, magnetomotive force harmonic content, and induced rotor losses, as well as the capability to limit the short-circuit current and other fault-tolerance features. Considering these characteristics, this paper aims to help the PM machine designer to select the proper winding configuration, giving useful indications. The winding choice criteria are given using analytical equations, so that their implementation is easy. In this way, the collection of such criteria becomes a helpful tool in the design process.
This paper presents a method to evaluate the economic feasibility of tractor powertrain electrification based on life cycle cost analysis. For a parallel hybrid, the best combustion engine ...downsizing, among some discrete values, was evaluated. The methodology was applied to three case studies with different power levels and operating cycles: a 76 kW orchard tractor, a 175 kW row crop tractor with medium duty use, and a 210 kW row crop tractor with heavy duty use. Fuel and electrical energy consumption were estimated through simulation. A range of powertrain components prices and fuel and electrical energy prices was taken into account, in order to cover price uncertainty and to show its effects. The results show that operating cost savings decrease when more power-intensive operations are performed. Considering a combination of system and energy prices deemed realistic by the authors, the operating cost savings, respectively for orchard, row crop medium duty, and row crop heavy duty, are approximately 8%, 3%, and 0.5%, which result in 6%, 1%, and 0.1% life cycle cost savings. Thus, powertrain electrification of high-power tractors should probably be avoided, whereas it could be beneficial for specialized orchard tractors. The developed method has proved to be suitable for such analyses.
Crop models are used to estimate crop productivity under future climate projections, and modellers manage uncertainty by considering different scenarios and GCMs, using a range of crop simulators. ...Five crop models and 20 users were arranged in a randomized block design with four replicates. Parameters for maize (well studied by modellers) and rapeseed (almost ignored) were calibrated. While all models were accurate for maize (RRMSE from 16.5% to 25.9%), they were, to some extent, unsuitable for rapeseed. Although differences between biomass simulated by the models were generally significant for rapeseed, they were significant only in 30% of the cases for maize. This could suggest that in case of models well suited to a crop, user subjectivity (which explained 14% of total variance in maize outputs) can hide differences in model algorithms and, consequently, the uncertainty due to parameterization should be better investigated.
•Five crop models and 20 users were arranged in four randomized blocks.•The significance of model factor for maize and rapeseed was evaluated.•All models achieved good performance for maize and poor for rapeseed.•Differences between models were significant only in 30% of the cases for maize.•Parameterization uncertainty should be explicitly managed also in model ensembles.
An auto-tuning and self-adaptation procedure for High Frequency Injection (HFI) based position and speed estimation algorithms in Interior Permanent Magnet Synchronous Motor (IPMSM) drives is ...proposed in this paper. Analytical developments show that, using conventional approaches, the dynamics of the high-frequency tracking loop varies with differential inductances, which in turn depend on the machine operating point. On-line estimation and adaptation of the small signal gain of the loop is proposed here, allowing accurate auto-tuning of the sensorless control scheme which does not rely on a priori knowledge of the machine parameters. On-line adaptation of Phase-Locked Loop (PLL) gains and of the injected voltage magnitude is also possible, leading to important advantages from the performance, loss and acoustic point of view. The theoretical basis of the method has been introduced first and the main concept demonstrated by means of simulations. Implementation has been carried out using the hardware of a commercial industrial drive and two Interior Permanent Magnet Synchronous Motors, namely a prototype and an off-the-shelf machine. Experimental tests demonstrate the feasibility and effectiveness of the proposal.
This paper presents the validation of a small-signal finite-element simulation strategy comparing different simulation approaches. At first, a full 3-D non-linear model in the time domain is ...presented. Then, the small-signal strategy has been applied to the 3-D model achieving a considerable reduction of computational time. In both 3-D models, the eddy currents in the laminations are fully modeled. Then, in order to avoid 3-D model, a 2-D model has been considered. In this case, eddy currents are included adopting a homogenization technique. In the 2-D case, both non-linear time domain simulations and small-signal strategy have been implemented. The results of the four considered simulation strategies are in very good agreement, proving that the small-signal simulation strategy can be profitably used in order to reduce significantly the computational cost. As an example, this paper considers a two-port mutual inductor as a test model.
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