Enhanced Stray-Load Loss Measurements Through a Zig-Zag Variable Load Test Approach

This article proposes an enhanced procedure for executing the standard variable load test that allows obtaining high correlation factors for indirectly measured stray-load loss during efficiency tests of induction motors. This helps to achieve the minimum values required by the international standards to consider the variable load test well executed, avoiding unwelcome test repetitions and leading to significant amount of time saved. With the machine at steady-state temperature, the enhanced procedure consistsofalternativelyapplyingloadlevelshigherandlowerthan the rated load, so that the stator winding temperature zigzags aroundtheratedvalue.Hence,multiplereadingscanbeperformed for each load point, having the machine in isothermal conditions. This allows averaging many measurements of the same load point to mitigate the impact of instrumentation and reading errors. The article includes load tests conducted on different induction motor sizesandpolecounts,applyingboththestandardvariableloadtest procedure and the proposed approach. The experimental results show that theproposed technique allows achieving higher correlation factors on the stray-load losses than the standard procedure

Electrical Machine Topologies: Hottest Topics in the Electrical Machine Research Community

In this article, the state of the art in electrical machine design is outlined underlining the problems and challenges to be solved by engineers. As highlighted in this article, even if electrical machine design is often considered a mature issue from the technical and technological point of view, every year, new progresses and steps forward are made. New and more sophisticated design tools can be used worldwide, and innovative manufacturing processes, new insulation materials, and higher performance magnetic materials are available on the market. In addition, the evolution of the hardware used in digital control and new powerful power electronic devices represents a constant stimulus to improve the performance of electrical machines and reintroduce electrical machine structures that were not adopted in the past due to technological and technical constraints. As shown in this article, electrical machine design is an evergreen topic, and its importance is rising more each year under the push of more energy-saving requirements and higher-efficiency systems for electromechanical conversion. A green world will not be possible without electrical machines

A direct-drive wave energy converter with contactless force transmission system

Commonly proposed ocean wave energy converters (OWEC) use inefficient and maintenance demanding intermediate hydraulic and pneumatic systems. We propose a novel rotary direct-drive OWEC that eliminates these intermediate stages. The new device employs a contactless force transmission system (CFTS) comprising a “piston” and a “cylinder” and a ball screw to spin a conventional rotary generator. We present an analytical model of the OWEC and also propose a numerical technique that performs a coupled fluid-structure interaction simulation of the wave energy device in a 3-D numerical wave flume using a computational fluids dynamics (CFD) code. In previous investigations, the motion of floating bodies was prescribed rather than determined. The current method represents a significant advancement in that it determines the motion of the buoy from the dynamic solution of the fluid flow problem and the dynamic buoy motion problem. The technique was extended to assess the performance of two neighboring buoys and their interference effects.Keywords: direct-drive, ocean wave energy, fluid-structure interactio

Electrical machine topologies: hottest topics in the electrical machine research community

n this article, the state of the art in electrical machine design is outlined underlining the problems and challenges to be solved by engineers. As highlighted in this article, even if electrical machine design is often considered a mature issue from the technical and technological point of view, every year, new progresses and steps forward are made. New and more sophisticated design tools can be used worldwide, and innovative manufacturing processes, new insulation materials, and higher performance magnetic materials are available on the market. In addition, the evolution of the hardware used in digital control and new powerful power electronic devices represents a constant stimulus to improve the performance of electrical machines and reintroduce electrical machine structures that were not adopted in the past due to technological and technical constraints. As shown in this article, electrical machine design is an evergreen topic, and its importance is rising more each year under the push of more energy-saving requirements and higher-efficiency systems for electromechanical conversion. A green world will not be possible without electrical machines

Electrical Machine Topologies: Hottest Topics in the Electrical Machine Research Community

n this article, the state of the art in electrical machine design is outlined underlining the problems and challenges to be solved by engineers. As highlighted in this article, even if electrical machine design is often considered a mature issue from the technical and technological point of view, every year, new progresses and steps forward are made. New and more sophisticated design tools can be used worldwide, and innovative manufacturing processes, new insulation materials, and higher performance magnetic materials are available on the market. In addition, the evolution of the hardware used in digital control and new powerful power electronic devices represents a constant stimulus to improve the performance of electrical machines and reintroduce electrical machine structures that were not adopted in the past due to technological and technical constraints. As shown in this article, electrical machine design is an evergreen topic, and its importance is rising more each year under the push of more energy-saving requirements and higher-efficiency systems for electromechanical conversion. A green world will not be possible without electrical machines

Electrical machine topologies - hottest topics in the electrical machine research community

Electrical machines are generating and using most of the electrical energy converted worldwide from fossil fuels or renewable sources. An optimized electrical machine means not only less input energy used but also higher electromechanical energy available as output. This is translated into getting more with less and having an impact on the total amount of greenhouse gases released into the atmosphere, thus mitigating global warming. Benefiting from the latest developments in the electrical machine field are various industries such as electric propulsion [new electric vehicles (EVs) and plug-in hybrid EVs (HEVs)], renewable energy harvesting, consumer applications, and military and aerospace products. This article brings together the contributions from several authors working in academia and industrial research and development centers and comprises a collection of short analyses dedicated to the hottest topics in the electrical machine research community. The article focuses on special and difficult problems to be solved in the design process of the most important electrical machine topologies. The topics discussed cover new machine topologies such as fractional slot winding motors and synchronous reluctance motors; electromagnetic, mechanical, and thermal problems in permanent magnet (PM) machines design; operation of high-speed machines and high-power turbo generators; noise and vibration reduction in switched reluctance motors (SRMs) for automotive applications; high-efficiency induction machines (IMs) configurations compatible with the new international standard and a comprehensive analysis of universal motors (UMs). Illustrated with significant experimental data and images of various machine configurations, this article is bringing into the spotlight the less well-known details related to the design, manufacturing, and operation processes of electric machinery. A fresh view on the systems in which the electrical machines are integrated is the main common factor in this collective and complex work