Optimum Speed Calculation for Electrical Machine Optimization in Variable Speed Applications
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Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slot-less, external rotor, permanent magnet machines are used in these systems as Motor/Generator. Commonly, optimizations of electrical machines are done in constant, nominal speed. But Electro-Mechanical Batteries are variable speed system. The efficiency is variable versus time, so, optimization in each single speed cannot necessarily cause the overall efficiency optimization. In this study, iron and copper losses are formulated versus speed variations of rotor. Then, for energy optimization, the optimization speed is achieved by equalizing the average iron loss and copper loss over a period of charge and discharge.Keywords:
Copper loss
Rotor temperature of large generator is indirectly obtained by analyzi ng and calculating the voltage and current values acquired from the rotor. Detec ting device is developed using PLC and touched screen. The operation of the devi ce is easy and the interface is friendly. Now it's operating in the power plant.
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The over voltage of rotor happened in a 100MW water-cooled generator.And it is different obviously with another same type generator.In this paper,the trend of over voltage is analyzed and the hidden trouble is found.The temperature trend of cooling water in different generator is different.Finally,the treat method is put forward.
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The products and manufacturing processes of newly developed rare earth bonded magnets are highlighted for isotropic Nd Fe B based magnet,anisotropic Nd Fe B magnet,and Sm Fe N system magnets including SmFe 7N x+α Fe exchange spring magnet and injection molded Sm 2Fe 17 N 3 anisotropic magnet.The recent works concerning rare earth bonded magnets are also presented.
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Attraction between a pair of rare earth-cobalt magnets is very useful for retention of dental prosthetic appliances. In these applications, the space available for embedding magnets is very narrow. Therefore, the magnets must have those optimum dimensions which cause the mximum attraction. The optimum dimensions are calculated for a rectangular or disk magnet pair utilizing the axial or radial attraction. In order to maximize the axial attraction of a magnet pair in small separation, the rectangular magnet must be slender and the square or disk magnet must have a size ratio of about OA, which is defined as the ratio of thickness to length of edge or diameter of the magnet. In the case of radial attraction, the optimum disk magnet has a little larger size ratio, e.g., about 0.55 in zero separation. Based on these theoretical analyses, the method of designing the optimum magnets with a required attraction is proposed.
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Electropermanent magnet
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The rotor is one of the most important parts in the generator,its performance will directly affect the working efficiency and long-term safe operation of generator. Thus the simulation and analysis of the generator rotor is the basic work of the performance analysis and structural optimization of the generator. In this paper,the QFW-25-4 generator of Nanyang Explosion Protection Group is selected,and the details of process,methods and techniques of three-dimensional modeling of the rotor are presented. Then the exact three-dimensional solid model of the rotor will be used in the simulation of the rotor next.
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The relible winding quality is the guarantee of large and high speed generator.The manufacture quality of winding is improved effctively by the modification of the manufacture process of rotor winding,which break the development bottleneck of the enterprise.The enterprise can improve the manufacture ability from the 500kW generator to the 3200kW generator,and thus achieves good economic benefit.
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In large generator rotor temperature directly unpredictable situation,made a kind of indirect temperature measurement principle,namely the use of the relationship between resistance and temperature,resistance and voltage,current relationship,through the measured winding voltage,current,and then converted the rotor temperature.The specific implementation methodology is based on the principle of indirect temperature measurement,select the necessary hardware,to build measure devices,and then be written the software to achieve the purpose of generator rotor temperature.The on-site test and simulation concludes that this method is simple,feasible and reliable.
Shunt generator
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In induction motor no‐load test, the no‐load losses usually include the stator copper loss, iron loss, the friction, and the windage losse, and the stray loss, and the rotor aluminum loss often is ignored. In this paper, a new method that separates the rotor aluminum loss from the no‐load losses is mentioned. Although, in IEEE Standard 112 and IEC34‐2, the rotor aluminum loss is neglected in no‐load test. However, in proposed method, the rotor aluminum loss is considered as an important part of the no‐load loss. Therefore, this paper intends to develop a new testing method to obtain the rotor aluminum loss under no‐load condition. In this case, six induction motors of the same kind (3 kW, four‐poles) are chosen to carry out no‐load and ideal no‐load tests. Through the comparative analysis of experimental data, the no‐load rotor aluminum loss accounts for about 13.4% of the no‐load loss, and the test approach can also explain that this part loss is not generated by higher harmonics. Based on these results, this paper demonstrates that the rotor contact resistance has great influence for the no‐load rotor aluminum loss, and a rotor resistance analysis model with rotor contact resistance is proposed. Final, the proposed method offers the possibility of taking measures on rotor resistance to improve motor efficiency. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.
Windage
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Squirrel-cage rotor
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Both the motor with cast copper rotor and variable frequency conversion motor has its own structure characteristics and design methods, and the combination of them will make the loss calculation complex, so it should be restudied. Based on the characteristics of motor with cast copper rotor and variable frequency conversion motor, this paper focuses on the loss calculation method of frequency conversion motor with cast copper rotor. The paper analyzes and calculates the stator copper loss, rotor copper loss, iron loss and stray loss successively. Finally, the experiment result is given out, and the loss calculation method is verified in directly.
Copper loss
Squirrel-cage rotor
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