Earlier measurements in large synchronous generators indicate the existence of backward whirling motion, and also relatively large deviations of shape in both the rotor and the stator. These non-symmetric geometries produce an attraction force between the rotor and the stator, called unbalanced magnetic pull (UMP). The target of this paper is to analyse the whirling frequencies and amplitude of the response for large synchronous generators with a high number of poles, due to deviations of shape in the rotor and stator. A mathematical model is developed to describe the shapes of the rotor and stator, and the corresponding UMP is obtained by using the law of energy conservation. The UMP is analysed due to different deviations of shape. The result gives the average angular frequency and the magnitude of the UMP for certain deviations of shape. From this result, the whirling frequency and the amplitude of the corresponding response can be approximated. Simulations of the response of a Jeffcott rotor model show good agreement with the theoretical results of the UMP for some generator geometries. The conclusion is that different whirling frequencies, both backward and forward whirling, can occur in these machines due to deviations in shape of the generator. Therefore, the shape of the generator can excite resonance vibrations on several other frequencies than the rotation frequency. During maintenance of hydropower generators the shapes of the rotor and stator are frequently measured. The results from this paper can be used to evaluate such measurements and to explain the existence of complicated whirling motion. 相似文献
Hf3As has a monoclinic unit cell of dimensions a = 15.3898(14) Å, b = 5.3795(5) Å, c = 15.330(14) Å, β = 90.291(6)°. A structure proposal based on space group (No. 15) has been refined by the least-squares method using a Rietveld-type fullprofile analysis of Guinier-Hägg X-ray powder film intensity data. The Hf3As structure is an intermediate between the Fe3P and the Ti3P types. The atomic coordination follows rules formulated earlier for representatives of the Fe3PTi3PV3S family of structures. 相似文献
A number of monopodands havingo-diphenylphosphinyl terminal groups were synthesized by alkylating sodium derivatives of oligoethylene glycols witho-(bromomethyl)phenyldiphenylphosphine. The stability constants of the complexes of these ligands with alkali metal cations at 25 °C were determined conductometrically in a THF—chloroform solution (41, v/v). The complexing ability of monopodands with respect to the cations studied increases monotonically as the number of electron-donating sites increases (from 3 to 8) for all of the cations except Li+ and, to some extent, Na+. In the case of Li+ a smooth decrease in the stability of the complexes is observed. The monopodands obtained in this work differ drastically in this regard from their structural isomers, bis[o-(diphenylphosphinylmethyl)phenyl] ethers of oligoethylene glycols, which had been studied previously.For part 10, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 952–956, May, 1993. 相似文献
Conclusions The seven-membered heterocycle in 2H-3,4-dihydro-3-phenyl-3-oxo-1,5,3-benzodioxaphosphepine was found to have twist conformation by x-ray diffraction structural analysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskya, No. 5, pp. 1150–1152, April, 1989. 相似文献
Chemical fourling on the unit-cell level is introduced as a structure-building operation in the solid state. A chemical fourling structure is achieved when two twin planes are perpendicular to each other. Each fourling unit has infinite extension in only one direction and can be related to a well-known structure type or packing of atoms. The structures of the tetragonal tungsten bronzes MxWO3 and Pd(NH3)4Cl · H2O are presented as examples of chemical fourlings of cubic close packing. The structures of SeO2, Mn2Hg5, and Zr2F7O are shown to be a sequence of chemical fourlings of primitive cubic packing. Chemical fourling units of hexagonal close packing are found in the structures of tetragonal Ti3Sb, α-V3S and Sb6O7(SO4)2. The structures of CuAl2, SeTl, NbTe4, Ti3Sb, and MnU6 all have the same chemical fourling unit. Cr23C6 is described as a bounded chemical fourling of cubic close packing. 相似文献
The crystal and molecular structure of 2-phenoxy-25-2,2(3H,3H)-spirobi[1,3,2-benzoxazaphosphole] has been determined using X-ray diffraction structure analysis. The P atom in the molecule in question has a distorted trigonal bipyramidal coordination, with the bond lengths P-Oax=1.701(1) and 1.700(1) Å, P-Oeq (Ph)=1.625 Å, P-Neq=1.654(2) and 1.645(1) Å, and bond angles (O-P-O)ax=175.69(7)° and (N-P-N)eq = 132.38(7)°.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 876–879, May, 1993. 相似文献
A convenient synthesis of Fucα1-2Galβ1-3GalNAcβ-OCH2CH2CH2NH2 (trisaccharide H type 4) is described. This glycan is the terminal part of glycosphingolipids globo-H and fucosyl-GM1 known as cancer-associated carbohydrate antigens. 相似文献
Blood group B antigenic trisaccharide-beta-aminopropyl glycoside (B-TSAP) covalently attached to poly-N-(2-hydroxyethyl)acrylamide-coated porous glass interacts with anti-B monoclonal antibodies faster than the ligand coupled to CNBr-activated Sepharose 4B and Affi-Gel 10. Rates of hydrophobic adsorption of antibodies on the butyl derivatives of the same supports were measured to evaluate the diffusion input to overall kinetics. The lowest average affinity adsorption time [t1(aff) = 250 s] observed for polymer-coated glass probably arises because of the flexibility of the extended segments of chemisorbed N-substituted polyacrylamide acting as effective spacer arms. 相似文献
O-Sialylation of a substituted indolin-3-one under phase-transfer catalysis conditions, which does not occur when N-acetylsialyl chloride is used, proceeds with N,N-diacetylsialyl chloride as the glycosyl donor. A study using dynamic light scattering of solutions of both sialyl chlorides under conditions close to the conditions used for glycosylation showed a difference in the correlation radii of light scattering particles in such solutions. This suggests that the introduction of an additional N-acetyl group into the sialyl chloride significantly alters the structure of the supramers of glycosyl donor, which apparently have an increased accessibility of individual molecules for the attack by a nucleophile, which increases its reactivity.