Slot effect in synchronous reluctance motors with permanent magnet assisted (SR-PM) are deeply analyzed, reduced and verified by experiments in this paper. The three different type sample SR-PM motors are introduced f...
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Slot effect in synchronous reluctance motors with permanent magnet assisted (SR-PM) are deeply analyzed, reduced and verified by experiments in this paper. The three different type sample SR-PM motors are introduced firstly. Then how the rotor layer numbers affect the torque characteristics is deeply analyzed, including the torque-angle, steady operating torque and position-setting torque. Then the reduction method is presented with simulation results. The detail experiment results are given in the final. The results shows that both more layers and stator slot skewing can reduce the teeth harmonics. However for the rotor with sintered NdFeB magnet, stator slot skewed is the best way because it only has few layers due to manufacture reason
The finite element method is a kind of discrete numerical method, whose speed and precision greatly depend on the efficiency and accuracy of mesh generation. Parameter mapping method (PMM) consumes less computing time...
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The finite element method is a kind of discrete numerical method, whose speed and precision greatly depend on the efficiency and accuracy of mesh generation. Parameter mapping method (PMM) consumes less computing time, and has widely applicable fields. However, when the change of surfaces curvature is sharp, the PMM cannot ensure the quality of the finite element mesh. To avoid this case, this paper puts forward a quadratic mapping method of mesh generation based on traditional PMM. The new mapping plane is applied by the sides and diagonals on the surface, which is named the quadratic mapping plane relative to the parameter plane. The mesh generated on the quadratic mapping plane is mapped into the surface through the inverse quadratic mapping algorithm. The quadratic mapping method can preserve the geometrical shape of the original surface and generate mesh on the cutting surface. This method is applied extensively to the mesh generation on the automobile panel, and the efficiency of this method is proved by examples.
A fast template method (FTM) based on the template library (TL) for mesh generation is presented and introduced into the independently developed commercial code KMAS (King-mesh Analysis System) of sheet metal forming....
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A fast template method (FTM) based on the template library (TL) for mesh generation is presented and introduced into the independently developed commercial code KMAS (King-mesh Analysis System) of sheet metal forming. According to the difference of discrete points of boundary, the FTM can match the template in the TL and generate the finite element meshes. If the program can not find a suitable template from the TL, a new template will be constructed by Transfinite Interpolation algorithm, and the new template will be put into the TL. The FTM can generate triangle or quadrangle meshes rapidly for complex automobile panels. controlling ability of mesh density, excellent mesh quality and efficiency are the merits of the FTM.
In the AC adjusting speed system, the significant current impulse frequently occurs in the starting process while the output torque is sufficient. This would damage the power electronics device, cause the unbalance of...
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In the AC adjusting speed system, the significant current impulse frequently occurs in the starting process while the output torque is sufficient. This would damage the power electronics device, cause the unbalance of neutral point in three-level NPC topology, and deteriorate the starting performance. In this paper, a DC pre-excitation strategy, which limits the starting current and enhances the electromagnetic torque via establishing the flux linkage before starting process, is proposed to the three-level inverter under analysis on the mechanism of the above large current. The relevant experiments present its eminent effect on the 380 V/160 kW inverter-motor system. Also this paper discuss the feasibility of its application in high voltage high power inverter.
A physical value mapping （PVM） algorithm based on finite element mesh from the stamped part in stamping process to the product is presented, In order to improve the efficiency of the PVM algorithm, a search way from...
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A physical value mapping （PVM） algorithm based on finite element mesh from the stamped part in stamping process to the product is presented, In order to improve the efficiency of the PVM algorithm, a search way from the mesh of the product to the mesh of the stamped part will be adopted. At the same time, the search process is divided into two steps： entire search （ES） and local search （LS）, which improve the searching efficiency. The searching area is enlarged to avoid missing projection elements in ES process. An arc-length method is introduced in LS process. The validity is confirmed by the results of the complex industry-forming product.
This paper investigates the equivalent model for the friction boundary condition between blank and holder during sheet metal forming simulation, and proposes an equivalent algorithm, the thickness threshold value algo...
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This paper investigates the equivalent model for the friction boundary condition between blank and holder during sheet metal forming simulation, and proposes an equivalent algorithm, the thickness threshold value algorithm, for the first time based on thickness weighting. This algorithm assumes that the holder clearance is uniform during sheet metal forming; and the main reason for the unevenness of friction force distribution under the holder is that the uneven deformation of the blank leads to its uneven thickness distribution, which makes the local pressure on the blank distributed unevenly. The algorithm proposed in this paper can effectively simulate the influence of the unevenness on the forming process. Validity of this algorithm is verified by a comparison between the simulation results and the experimental ones for the drawing process of a car spring base.
作者：
HU Min ZHANG Jing WU ZhijunState Key Joint Laboratory of Environmental Simulation and Pollution Control
College of Environmental Sciences Peking University Beijing 100871 China State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences Peking University Beijing 100871 China State Key Joint Laboratory of Environmental Simulation and Pollution Control College of Environmental Sciences Peking University Beijing 100871 China
Totally 23 precipitation samples were collected in Beijing from May to November in 2003. In order to investigate the chemical composition of precipitation samples, pH, conductivity, concentrations of water-soluble ion...
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Totally 23 precipitation samples were collected in Beijing from May to November in 2003. In order to investigate the chemical composition of precipitation samples, pH, conductivity, concentrations of water-soluble ions and organic acids were analyzed. The average pH of pre-cipitations is 6.18, belonging to the neutral range; the average conductivity is 52.23 μS/cm, which indicates that precipitations in Beijing are obviously polluted; SO 24? , NO3 ? are the most abundant anions with the average concentrations of 521 and 174 μeq·L?1, respectively; the average 2SO 4? /NO3? equivalent ratio is 3.1, which decreases by about 15% compared with the result of 1994; NH+ 4 and Ca2+ are the most abundant cations with the average concentrations of 376 and 397 μeq·L?1, respectively; formic acid, acetic acid and oxalic acid are the main organic acids with the average concentrations of 4.62, 4.60 and 1.17 μeq·L?1, respectively, accounting for 2% of the overall anions. Obvious differences between concentrations before and after precipitation are also observed by SJAC (Steam Jet Aerosol Collector), which shows the removal of particles from the atmosphere by precipitation.
Volatile organic compounds(VOCs)are important precursors of atmospheric chemical *** a whole mixture,the ambient VOCs show very strong chemical *** on OH radical loss rates in the air,the chemical reactivity of VOCs i...
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Volatile organic compounds(VOCs)are important precursors of atmospheric chemical *** a whole mixture,the ambient VOCs show very strong chemical *** on OH radical loss rates in the air,the chemical reactivity of VOCs in Beijing was *** results revealed that alkenes,accounting for only about 15%in the mixing ratio of VOCs,provide nearly 75%of the reactivity of ambient VOCs and the C4 to C5 alkenes were the major reactive species among the *** study of emission characteristics of various VOCs sources indicated that these alkenes are mainly from vehicle exhaust and gasoline *** reduction of alkene species in these two sources will be effective in photochemical pollution control in Beijing.
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