The performance analysis and calculation for variable frequency speed control motors with the rotor structure optimized

In the paper, the method to optimize the rotor structure in variable frequency speed control motors is introduced. The saturation and the skin effect are considered and 2D no-load and load electromagnetic field is calculated in finite elements for a variable frequency speed control motor before and after optimization. Finally, no-load current and operation performance before and after optimization are obtained and the two results are contrasted.

The Applications of High-voltage variable frequency speed regulation System in Main Exhauster of Sintering

Main Exhauster is one of the main equipment of sintering production. It needs to consume a lot of electricity. Therefore, the system＇ s reconstruction for energy-saving will effectively reduce electricity for the production. The paper takes an iron and steel enterprise that had successfully transformed the synchronous motors of main exhauster of sintering as an example, which describes the application of high-voltage variable frequency speed regulation system in main exhauster of Sintering, so as to provide a reference for other iron and steel enterprises.

The Control System Simulation of Variable-Speed Constant-Frequency Wind Turbine

In general,Variable-Speed Constant Frequency (VSCF)Wind generation system is controlled by stator voltage orientation method which based on the mathematic model of VSCF Wind generation system and discussed the control strategy.Present the whole dynamic control model of variable-speed wind generator system in MATLAB/ Simulink,and the simulation results confirm the validity and effectiveness of the proposed control strategy.

Cavitation Detection in Variable Speed Pump by Analyzing the Acoustic and Vibration Spectrums

Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.

On maximum power point tracking control strategy for variable speed constant frequency wind power generation

Based on the characteristic of AC-excited variable speed constant frequency(VSCF)wind power generation,the vector control technique was applied in a doubly fed induction generator(DFIG).Maximum wind energy or maximum output power point can be tracked by decoupling control of active power and reactive power.The research result shows that the net power of generation system delivered to grid in maximum wind energy tracking mode is not the most.We presented a novel maximum power point tracking(MPPT)control strategy by analyzing the DFIG mathematic model and power relations which delivered the maximum power to the grid.The maximum power point could be tracked automatically without measuring wind speed in the control strategy and the control was independent of optimal turbine power curve,which had excellent dynamic and static performances and robustness.Simulation and experimental results testify the accuracy and validity of the control strategy.

A Recursive Method of Time-Frequency Analysis for the Signal Processing of Flutter Test with Progression Variable Speed

Focused on the non-statlonarity and real-time analysis of signal in flutter test with progression variable speed （FTPVS）, a new method of recursive time-frequency analysis is presented. The time-varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the method are examined by digital simulation. The results of FTPVS at low-speed wind-tunnel promise the engineering application perspective of the method.

Analysis of Electrical and Non-electrical Causes of Variable Frequency Drive Failures

VFDs （variable frequency drives） are an integral part of many industrial plants and stations. Reliable operation and maintenance of these drives is vital to ensure sustained plant operation and availability. Understanding of the principles of operation of VFD systems as well as knowledge about their required operating environment is necessary for all operating personnel. Many times the operating personnel do not get involved with different technical issues until a complete failure has occurred. Hence, the awareness of the most dominant failure causes has a significant impact on assisting operators to avoid catastrophic failures and tremendous economic losses due to VFD shutdown. Proper plant design, accurate monitoring and data logging, following manufacturer preventive maintenance schedule, and choosing qualified team of operators can be the key to an efficient operation and a long lifetime for any VFD system. In this paper, we have analyzed the electrical and non-electrical causes of VFD failures based on a case study of a typical medium voltage VFD pumping station. Finally, recommendations are given from field analysis and observations.

ASSESSMENT OF AN ELECTRO MECHANICAL DIFFERENTIAL GEAR PROVIDING VARIABLE SPEED TO INDUSTRIAL APPLICATIONS

当前,标准工业应用对于整体传动系统效率的要求日益提高,如压缩机、鼓风机、风扇及水泵。现有的系统如VFD或液压变速控制系统不能满足能源成本的需求。几年前一个创新性的变速系统EMDS(机电差速系统)出现在市场上,在总效率和初始成本上显示出巨大的潜力。该系统由一个主驱动(直接连接电网)、一个包含行星齿轮级的齿轮箱和一个伺服变频控制驱动组成。伺服驱动(最大为系统总功率的20%)通过主驱动的恒定速度来控制齿轮箱输出速度。此外这一设置使得电力元件最少化同时在整个传动当中占用空间小。研究表明,该系统可应用于最高至15MW和15 000r/min速度的变速应用上。长期运行将证明,该方案是否能安全满足工业的高标准和需求。作者对比了EMDS和其他变速系统的技术优势,并分析了EMDS的技术原理并包括详细的效率对比。此外还给出了实际应用证明案例。

A New Formula of Redshift vs. Space Expansion and Dark Energy

The speed away of stars and galaxies is traditionally calculated from the relativistic formula according to the measurement of the redshift. It is demonstrated here another formula for this speed away of stars and galaxies, from this same redshift z. After having exposed critiques on the demonstration and the relativistic use which require the assumption of an expanding universe by itself, it is proposed within the framework of neo-Newtonian mechanics the formula where V is the speed from the source. This formula has the double characteristic of being equivalent to relativistic predictions for low redshifts, but of deviating from them by up to 17% for high redshifts. It is consistent with the observation of the anisotropy of the Universe and the Cosmic Microwave Background. It helps to explain Pioneer anomalies. It is compatible with the constancy in the majority of cases of interference phenomena. Finally, it provides a new analysis grid for the observation of supernovae, galaxies and distant pulsars, thus opening up new fields of research on the increase in distances attributed to dark energy and also in other areas of the cosmology.

High-Power-Factor Adjustable Speed Drive Using Diode Clamped Multilevel Inverter

This paper presents a new approach to alleviate the harmonics and to enhance the power factor of the ASD （adjustable speed drive）. A conventional ASD with 2-level PWM （pulse width modulation） inverters generate high dv/dt and high frequency common mode voltages which are harmful for the drive applications. It reduces the motor bearings life and conducted EMI （electro magnetic interference） deteriorates the insulation. In this paper, a diode clamped multilevel （3-level） inverter is used to perform dual task. It generates HF （high frequency） current to be injected at the input of the three-phase front-end rectifier thereby improving the harmonic spectra and the power factor. It also drives the induction motor. The salient feature of this paper is that it does not require separate converters for improving power factor and to drive induction motor. Furthermore, inverter switches operate with ZVS （zero voltage switching）, thus reducing the switching losses substantially, The voltage stress of the switches also has been reduced to half of the conventional 2-level converter. The inverter is operated with SPWM （sinusoidal pulse width modulation） technique. The simulation results for a prototype of 2.2 kW are presented.

智能化视角下造纸机传动系统变频调速控制研究

在当今造纸行业向智能化转型的背景下,造纸机作为纸张生产的核心设备,其传动系统的高效运行对整体生产效率和产品质量起着决定性作用。电气自动化与变频调速技术的深入应用,极大地推动了造纸机控制系统的技术进步,为实现造纸机械高效、稳定生产提供了坚实的技术基础。基于此,在探讨造纸机传动控制系统的构成与设计关键点,并针对常见的变频调速技术进行分析,特别是直接转矩控制(DTC)算法在优化传动系统中减少异步电机电磁转矩波动、降低能耗、提升效率方面的应用,旨在为造纸机传动系统的优化提供切实可行的解决方案。

变转速下基于改进多阶概率方法的风电齿轮箱故障诊断研究

阶次跟踪是一种有效的解决变转速故障诊断问题的方法,其关键前提是存在转速信号作为参考。然而,由于强背景噪声和弱谐波关系的影响,现有转速估计方法的准确性和自适应性有待进一步提高。因此,提出一种融合多传感器信号的改进多阶概率方法(MOPA)用以估计瞬时转速。首先,依据不同传感器信号的基频统一性和主导分量差异性,通过时频图瞬时切片归一化融合的方式,构建具有强谐波关系的时频图;其次,为消除时变工况下时频图中横纵方向上的间歇恒频和短时宽频背景噪声,提出滑动消噪方法;最后,基于处理后的时频图执行MOPA,实现瞬时转速自动估计,结合阶次跟踪解决风电齿轮箱变转速故障诊断问题。经实测数据验证,改进MOPA估计的瞬时频率的准确性和自适应性均优于对方法,平均绝对百分比误差为0.56%,均小于对比方法的15.73%、13.99%和1.21%。结合阶次分析诊断了变转速下风电齿轮箱异常。

基于自适应窗口与压缩幅值的瞬时转频估计

针对变转速工况下轴承信号的时频分布能量发散、噪声和谐波干扰强导致其转频难以获取的问题,提出一种基于自适应窗口和压缩幅值的瞬时转频估计方法。首先,通过自适应窗口在频率轴方向搜索出脊线窗口避免噪声和谐波的干扰;其次,在脊线窗口内用压缩幅值方法集中发散的脊线能量;然后,用惩罚函数法提取脊线,实现转频的精确估计;最后,根据采用轴承实验台收集的数据验证了所提出方法的有效性和鲁棒性。结果表明,相比于传统方法,采用所提方法估计瞬时转动频率使误差降低约8%。

一种新型输出频率连续的交-交变频调速系统

针对传统交-交变频器功率器件多、控制复杂、功率因数低等缺点,在脉冲阻塞式交-交变频电路控制原理的基础上提出1种输出频率连续的交-交变频电路控制方法。首先给出三相输入三相输出和六相输入三相输出这2种交-交变频电路拓扑及其详细的工作原理。然后,搭建MATLAB/Simulink仿真环境下2种变频调速系统仿真模型进行仿真实验,仿真结果与理论分析相一致。最后,制作实验样机进行验证,实验结果证明了所提新型变频调速系统控制方法的有效性与可行性。

基于PLC的变频造纸机双闭环调速控制方法

为了提高变频造纸机的控制精度与稳定性,提出基于PLC的变频造纸机双闭环调速控制方法。首先,对变频造纸机的电机展开建模分析,为后续调速控制提供依据;其次,采用PLC技术设计变频造纸机控制系统,计算造纸机理想转速比,结合实际转速获得控制偏差,采用PI控制方式完成电流调节环节与转速调节环节的控制;最后,引入灰狼算法在变频造纸机双闭环调速控制目标函数的基础上优化PI控制参数,以此实现变频造纸机双闭环调速的优化控制。实验结果表明,在干扰环境中所提方法可高效、稳定地实现控制。

变频调速技术在自动控制系统优化中的应用

阐述变频调速技术在机械自动化控制中的应用,包括深度指示器、等速段超速、减速段超速的应用,以及匀速电机超速的保护。针对系统稳定性、调速精度、可靠性方面的问题,提出优化措施。

基于参数优化VMD和TET的柔直线路单端故障测距方法

单端行波故障测距方法在考虑频变波速影响时需要提取故障行波时频域特征,但现有方法存在时频分辨率较低、波头识别困难和波速计算不准确的问题。为此,提出一种基于参数优化变分模态分解(variational mode decomposition,VMD)和瞬态提取变换(transient extraction transform,TET)的单端故障定位方法。首先,利用麻雀搜索算法(sparrow search algorithm,SSA)优化VMD参数,提取含有故障特征的高频模态分量。然后,对该模态分量进行瞬态提取变换,通过去除短时傅里叶变换中模糊的时频能量,保留与信号瞬态特征密切相关的时频信息,得到故障行波时频域全波形。最后,在故障行波全波形中提取主频分量并标定初始波头与第二反射波头,通过计算主频分量下的波速度,结合行波定位方法实现单端故障测距。在PSCAD/EMTDC中搭建四端柔性直流电网的仿真结果表明,所提算法对过渡电阻和噪声具有较强的耐受性,即使在较低采样率下也能实现准确的故障定位。

FX高速包装机成品烟条输送装置的设计与应用

为解决FX高速包装机成品烟条输送过程中损耗高的问题,设计一种新的成品烟条输送装置。该装置主要由变频电机、输送链板、限位装置及下滑装置4个部分组成,通过传感器监控成品烟条的运输过程,出现成品烟条堵塞时立即停止包装机和输送链板,并实时调整变频电机的速度,实现成品烟条的均匀运输,减少停机次数;通过限位装置对成品烟条进行平衡、减速,保证成品烟条在下滑装置的运输过程中保持稳定,降低成品烟条的损耗。以某卷烟厂生产的实际为对象对该装置进行测试,结果表明,应用后成品烟条损耗降低30%,成品烟条滑落和掉落的问题降低到0,运输过程中成品烟条堵塞的次数减少70%,为提高FX高速包装机的高生产效率提供保障。

自适应窗口旋转优化短时傅里叶变换的变转速滚动轴承故障诊断

针对短时傅里叶变换(STFT)中固定窗效应所导致的能量集中度不高的问题,提出了一种自适应窗口旋转优化短时傅里叶变换(AWROSTFT)的变转速滚动轴承故障诊断方法。通过变分模态分解(VMD)对原始振动信号进行降噪,并利用粒子群优化算法(PSO)解决了VMD参数选择困难的问题;利用切线思想对STFT中水平窗口自适应匹配一系列的旋转算子,使得窗口旋转方向接近甚至等于瞬时调频率,提高了时频表示的能量集中度;计算出谱峰检测法提取到的瞬时频率与转频的平均比值,将得到的结果与轴承的故障特征系数进行匹配,以此实现变转速工况下滚动轴承的故障诊断。仿真和实验的结果都表明,本文所提方法能够兼顾PSO-VMD和AWROST-FT的优势,通过切线思想自适应的旋转窗口使得信号与窗函数在全局上的夹角都为零,从而达到提高能量集中度和锐化时频脊线的目的,实现了变转速工况下滚动轴承的故障诊断。