用检测转子频率的方法控制电机反接制动可靠停车

在较大设备的交流拖动频繁启、制动控制工艺中 ,如何迅速可靠停车是一个重要问题。利用检测电机转子频率的方法控制无触点系统实现了 45 0t冷剪机的反接制动稳定停车 ,方法简单 ,运行可靠。

一种新型搜索电机转子频率的方法

针对高压变频调速系统,提出了一种新型的"飞车起动"控制算法。该算法无需配置电压互感器及转速传感器,仅由定子电流幅值的大小即可快速搜索出旋转电机的转速。为了实现该功能,推导了维持定子电流恒定时,定子电压与输出频率、电机转速之间的稳态数学表达式,证明了定子电流与电机估计转速之间具有单调递增的函数关系,并获得了该函数关系成立的限制条件。在此基础上,在搜频过程中,算法根据设定的规律动态改变变频器的输出频率,提高了电机转子频率搜索的快速性和准确性。仿真结果验证了理论分析的正确性和所提方法的有效性。

绕线转子异步电动机转子频率鉴频调速

介绍了利用绕线转子异步电动机转子频率控制电机转速的新方法.文中阐述了这种新方法所用控制器的结构、工作原理;展示了原理波形.该控制器是静止的电子装置,可以替代常规的测速发电机,有很强的实用价值.

基于转子固有频率的涡轮泵故障检测方法

为了有效地检测液体火箭发动机涡轮泵的故障,分析了某型液体火箭发动机的28次历史试车数据,得到了涡轮泵转子的一阶、二阶和三阶临界转速以及轴向固有频率的数值,研究了这4个转子固有频率幅值的稳定性及对涡轮泵故障的敏感性,得出了它们具有较强的稳定性和故障敏感性的结论。在此基础上,提出并验证了基于转子固有频率的涡轮泵故障检测方法。结果表明,基于转子的一阶、二阶和三阶临界转速以及轴向固有频率幅值能有效地检测涡轮泵的故障。

惰行状态下的地铁PMSM转子初始位置辨识策略

永磁同步电机(PMSM)因其具有高效率、高功率密度等特点,成为新一代轨道交通牵引系统的发展方向,其中,惰行状态下的电机转子初始位置和频率辨识方法研究是PMSM无位置传感器控制技术的重要组成部分。因此,首先研究了零电压矢量单脉冲法和双脉冲法,当PMSM处于惰行状态时,通过将三相逆变器所有下桥臂短路1个或2个脉冲,根据短路响应电流获取转子初始位置和频率。在此基础上,提出一种零电压矢量脉冲法短路时间的选取方法和零电压矢量复合脉冲法,确保处于不同惰行频率下的PMSM均可以稳定地重新启动。通过Matlab/Simulink仿真及在中车大连电力牵引研发中心有限公司试验中心进行试验,结果表明:处于不同频率下的PMSM,均可以稳定地重新启动,启动时的频率辨识误差小于0.6 Hz,转子位置辨识误差小于5°。

异步电动机转子感应电势

本文从一个新的角度出发,推导出异步电动机转子电路感应电势的计算公式。推导过程比较简单、步骤完整、物理意义清楚、容易理解。对学生的学习很有帮助,反映良好。

运用COSMOSWorks/SolidWorks进行快捷转子动力学分析

简要介绍了一种采用COSMOSWorks/Solidworks进行转子动力学分析的方法,该方法较其它常见方法具有简单易学、易操作、准确度高等优点,非常适合工程技术人员日常使用,将使用过程中的难点加以分析,成功解决了弹性支持等难点问题。

高压变频器瞬时失电再启动的新型实现方法

随着变频调速系统应用领域的扩大,为避免高压变频器因配电系统瞬时失电对生产造成影响,瞬时失电再启动技术应运而生。该技术的关键在于电机转子频率的搜索,但现存的"按转矩电流分量最小"和"定子输入恒定额定电流比较"等搜索方式算法复杂、精度较低,对于VVVF控制变频器来说实现不易、性价比低。为此提出了采用轴编码器结合PLC实时跟踪电机转速的方法,理论分析及试验结果表明该方案易行、可靠性高,具有良好应用前景。

电磁吊车事故预防保护方案探讨

介绍了天津钢管集团有限公司装卸钢管和废钢用进口电磁吊车采用频率继电器SF1-LS304的功能原理和输出特性以及常见故障。探讨了装卸废钢用进口电磁吊车采用频率继电器检测绕线式异步电机转子频率,进行“反向制动电流”控制,“超同步速度降落”和“阻止再提升”控制的预防性保护方案。

Studies of Improving the Frequency of Indica Rice Transformation by Biolistic Bombardment

In order to improve the frequency of indica rice transformation by biolistic bombardment, suitable culture conditions for embryonic calli,an optimal selection scheme for resistant calli and seedlings, and optimum bombardment parameters a investigated by using 14 commercially important indica rice cultivars. The main results show that the CC medium with 36g/L mannitol is a scheme subculture medium in which the browning of indica rice calli can be mitigated significantly; The concentration of 30～40mg/L Hyg or 150～200mg/L G418 or 10～20 mg/L Basta is suitable for selection of resistant calli; The transformation parameters of 100μg gold powder absorbing 0.2μg DNA per shot and 900 psi helium pressure and 6 cm bombardment distance and bombarded twice for each plate give the best result; Keeping the target calli on osmotic medium containing 60g/L mannitol from 12 ～24h before bombardment to 24～48h after it can increase the efficiencies of transformation . Furthermore, some transgenic indica rice plants are obtained using this optimized transformation system.

三硫酸风机振动过大故障诊断

针对硫酸风机振动过大的故障,通过振动测试,发现振动值严重超标,利用锤击法,测试了风机转子的固有频率,排除了风机振动过大是由转速接近临界转速的可能,利用频谱分析技术,找出了故障产生的原因,提出了解决问题的方案和开展状态监测等建设性建议。

＂One-for-several＂ rotor VVVF Technique apply to water injection station

In the process of oilfield water injection volume of injection allocation often appear with the pump displacement situation does not match, the widespread adoption of stator frequency technology allows the pump displacement and volume of injection allocation phase matching. But the technology in pump class load application speed range is limited, there is still a reflux valve control blind area,＂ turn off undead＂ problem. ＂ One-for-several＂ rotor frequency Technique in water injection station application, solved the control blind area problem, the full realization of the variable frequency close return voltage injection, at the same time, the successful implementation of the slip power efficient feedback. Stable water injection pressure of the system, and the electric energy is saved, satisfy the oilfield high efficiency, fine water needs, has a high application value.

Inverse Perturbation Method for Inverse Eigenvalue Problem Based on Finite Element Analysis

An Inverse perturbation method is described for solving the general inverse eigenvalue problem. By taking the analysis of the rotor system as example based upon FEM, the new inverse perturbation method for structural design with specified low-order natural frequencies or frequency constraint bands is detailed as well as its complete theoretical basis. Moreover, formulations to calculate the inverse perturbation parameter ε and method to select the corresponding ε's value properly are also proposed. The proposed method is characterized in reducing frequency analysis and suitable for large and small structrual changes alike. Finally, several different numerical examples for inverse cigenvalue problem are discussed to illustrate the method, which show that this inverse perturbation method Is general and can be applied to other type of structure or dement.

Numerical and Experimental Research on the Influence of the Centrifugal Pumps Rotor Damage on Their Natural Frequency Response

The paper presents process of creating a centrifugal pump rotor model in CAD environment. Modeling of a virtual object was divided into two stages, modeling of the efficient pump and the simulated failure of one of the impeller＇s blades. Comparison of the results of the resonance frequency obtained from the model analysis, with those obtained from measurements on the actual object was shown. Measurements and simulations were conducted on the pump before and after the simulated damaged of the rotor. In order to verify the model the rotor of pump was weighted and compared with the masses of the respective components obtained from the virtual object. In the second stage genuine rotor was subjected to the experimental modal analysis.

Collective rotations of fission isomers in actinide nuclei

Using the total-Routhian-surface （TRS） method, the rotational behaviors of fission isomers in the second well of actinide nuclei 234-242U, 236-244pu and 238-246Cm were investigated. The pairing-deformation-frequency self-consistent TRS calculations repro- duced reasonably the experimental moments of inertia extracted from spectroscopic data. It is calculated that, in these largely elongated （β2 ≈0.65 and β4≈ 0.03） fission isomers, the ν1/2-[981] neutron and π1/2＋[651] proton align simultaneously at rotational frequency hω≈0.4 - 0.6 MeV （corresponding to spin I≈80h）, which leads to clear upbending in moments of inertia （MoI＇s）. Our calculations have indicated that the hexadecapole deformation f14 influenced significantly the frequency of the rotational alignment of the proton 1/2＋[651] orbit.

Single-photon detection and its applications

A single-photon detector is an extremely sensitive device capable of registering photons,offering essential technical support for optics quantum information applications.We review herein our recent experimental progress in the development and application of single-photon detection techniques.Techniques based on advanced self-differencing,low-pass filtering,frequency up-conversion and photon-number-resolving are introduced for attaining high-speed,high-efficiency,low-noise single-photon detection at infrared wavelengths.The advantages of high-speed single-photon detection are discussed in some applications,such as the laser ranging and quantum key distribution.The photon-number-resolving detection is shown to support efficient quantum random number generation.

Rotational properties of the odd-Z transfermium nucleus ^(255)Lr by a particle-number-conserving method in the cranked shell model

Experimentally observed ground state band based on the 1/2-[521] Nilsson state and the first exited band based on the 7/2-[514] Nilsson state of the odd-Z nucleus 255Lr are studied by the cranked shell model （CSM） with the paring correlations treated by the particle-number-conserving （PNC） method. This is the first time the detailed theoretical investigations are performed on these rotational bands. Both experimental kinematic and dynamic moments of inertia （f^（1） and ,f^（2） versus rotational frequency are reproduced quite well by the PNC-CSM calculations. By comparing the theoretical kinematic moment of inertia f（1） with the experimental ones extracted from different spin assignments, the spin 17/2- →13/2- is assigned to the lowest-lying 196.6（5） keV transition of the 1/2- [521 ] band, and 15/2→11/2- to the 189（1） keV transition of the 7/2- [514] band, respectively. The proton N = 7 major shell is included in the calculations. The intruder of the high-j low→lj15/2 （1/2-[770]） orbital at the high spin leads to band-crossings at hω = 0.20 （hω~=0.25） MeV for the 7/2-[514]ω= -1/2 （ω= ＋1/2） band, and at hω=0.175 MeV for the 1/2- [521 ] ω= - 1/2 band, respectively. Further investigations show that the band-crossing frequencies are quadrupole deformation dependent.

Effects of a Weakly Interacting Light U Boson on Protoneutron Stars Including the Hyperon-Hyperon Interactions

In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g^2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g^2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed.

Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction

We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings model.Here the frequency of the interacting field is sinusoidally varying with time with a constant phase.Due to the presence of phase in the frequency modulation,the variation of population inversion with time is different from the standard case.There are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with time.In coherent field atom interaction the population inversion behaves as in the case of Fock state atom interaction,when frequency modulation with a non zero phase is applied.The study done with squeezed field has shown the same behavior of the population inversion.

Investigation of the two-quasiparticle bands in the doubly-odd nucleus ^(166)Ta using a particle-number conserving cranked shell model

The high-spin rotational properties of two-quasiparticle bands in the doubly-odd 166Ta are analyzed using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency hw are reproduced very well by the particle-number conserving calculations, which provides a reliable support to the configuration assignments in previous works for these bands. The backbendings in these two-quasiparticle bands are analyzed by the calculated occupation probabilities and the contributions of each orbital to the total angular momentum alignments. The moments of inertia and alignments for the Gallagher-Moszkowski partners of these observed two-quasiparticle rotational bands are also predicted.