Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
Reliable induction motor (IM) fault detection techniques are very useful in\nindustries to diagnose IM defects and improve operational performance. An\nadaptive empirical mode decomposition (EMD) technology is proposed in\nthis paper for rotor bar fault detection in IMs. As the characteristic fault frequency\nwill change with operating conditions related to load and speed, the\nproposed adaptive EMD technique correlates fault features over different\nfrequency bands and intrinsic mode function (IMF) sidebands. The adaptive\nEMD technique uses the first IMF to detect the fault type and the second IMF\nas an indicator to predict the fault severity. It can overcome the problems of\nthe sensitivity of sideband frequencies related to the speed and load oscillations.\nThe effectiveness of the proposed adaptive EMD technique is verified\nby experimental tests under different motor conditions....
In a current source rectifier such as a matrix rectifier, input voltage and current cannot be\nin phase unless an additional input power factor control technique is implemented. This paper\nproposes such a technique for a matrix rectifier using power-based space vector modulation (SVM).\nIn the proposed method, the modulation index and phase required in order to apply the SVM are\ncalculated based on the active and reactive power of the rectifier for intuitive power factor control.\nThe active power that the rectifier should generate for the regulation of the output inductor current\nis obtained by the PI (proportional-integral) controller. The reactive power, which is supplied by the\nrectifier for adjustment of the power factor, is assigned differently depending on the output\ncondition: for the output condition capable of unity power factor, it is set to a negative value of\nreactive power of the input capacitor, and when the unity power factor is not achievable, it is set\nwith the maximum reactive power the rectifier can generate under the given condition to attain the\nmaximum possible input power factor. It is determined whether the given condition is the light load\ncondition by comparing the absolute value of the reactive power supplied by the input capacitor\nwith the maximum rectifier reactive power that can be produced under the given condition. The\nSVM based on the active and reactive power of the rectifier in this technique allows the input power\nfactor control to be intuitive and simple. The performance and feasibility of the technique were\nproved by simulation and experimentation....
The paper presents a comparative analysis of energy consumption by 2.2 kW electric\nmotors of various types and energy efficiency classes in the electric drive of a pump unit with\nthrottle control in a water supply system. Line-start permanent-magnet synchronous motors of the\nIE4 energy efficiency class and induction motors of the IE4 and IE3 energy efficiency classes of\nvarious manufacturers were considered (IE4 and IE3 are labels of energy efficiency classes of electric\nmotors according to IEC 60034-30-1 standard). Energy consumption at a hydraulic load changing\nunder a typical duty cycle was calculated based on the nameplate data of the pump and electric\nmotors. The developed method shows that selecting an electric motor based on the IE energy\nefficiency class under the IEC 60034-30-1 standard (i.e., based on efficiency at a rated load) may not\nprovide the minimum energy consumption of a variable flow pump unit over a typical duty cycle.\nIn particular, the considered IE4 class line-start permanent-magnet synchronous motors do not\nprovide significant advantages over IE4 class induction motors, and sometimes even over IE3 class\ninduction motors when they are used in variable flow pump units....
Lightning protection for blades is one of the most important factors for the safe operation of\nwind turbines. In view of the differences in the designs of blade receptors, a full-scale blade receptor\nmodel was constructed on the basis of the scaling experiment of the wind turbine and electrostatic\nfield theory. By combining the electromagnetic finite element analysis with leader discharge theory,\nthis study analyzed and discussed the influence of the protruding height of receptors and the design of\nreceptor types on the lightning receiving effect of the blade, and the optimum design scheme of blade\nreceptors was proposed. According to the results of this study, the field intensity distribution on the\nsurface of the receptor was a high-boundary and low-middle structure. The receptor easily produced\nan upward connection leader as the lighting junction. The electric field intensity around the receptor\nwas substantially distorted after 4 mm protrusion, which was approximately twice the electric field\nintensity of a flat right-angle receptor. The convex chamfer had multiple centralized lightning stroke\npoints compared with the convex right-angle design, thereby exhibiting better solidification and\nreliability at the lightning stroke area, which are conducive to protecting the blade from lightning\ndamage. The electric field intensity of the convex fillet was similar to the chamfer, but the radius\nof the electric field intensity of the convex fillet was small, and the attenuation of the electric field\nintensity with the radius was evident. This study provides a reference for further optimization design\nof blade receptors....
This paper reveals the optimum capacitance value of a receiver -side inductor -capacitor \n(LC) network to achieve the highest efficiency in a capacitive power -transfer system. These findings \nbreak the usual convention of a capacitance value having to be chosen such that complete LC \nresonance happens at the operating frequency. Rather, our findings in this paper indicate that the \ncapacitance value should be smaller than the value that forms the exact LC resonance. These \nanalytical derivations showed that as the ratio of inductor impedance divided by plate impedance \nincreased, the optimum Rx capacitance decreased. This optimum capacitance maximized the TX -to -\nRX transfer efficiency of a given set of system conditions, such as matching inductors and coupling \nplates....
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