异步电动机起动过程中转轴上的扭矩振荡现象研究

异步电动机带大惯性负载直接起动时,转轴上会产生很大的扭矩振荡.详细分析了产生扭矩振荡的原因,探讨了软起动对扭矩振荡的影响.仿真结果表明,采用晶闸管软起动装置可以在不影响电动机起动性能的前提下,有效抑制转轴上的扭矩振荡.     

异步电动机软起动过程中的振荡

针对异步电动机软起动过程中出现的电流、电磁转矩以及转速振荡问题,建立了其软起动通用仿真模型,分析了异步电动机软起动过程中引起振荡的影响因素及其产生原因,提出用控制关断角的方法,即以电流关断时刻为基准,在电机软起动过程中使关断角逐渐减小为零来抑制振荡。通过仿真验证了该控制方法的正确性,并在此基础上研制了基于关断角控制的异步电动机软起动装置并进行了样机试验,实验结果验证了理论分析的正确性。     

首钢京唐2250高压软起动装置调试工作安全分析

首钢京唐2250除鳞泵高压电动机（10kV）在起泵过程中,曾经发生过几次电动机放炮的严重事故。因此为了能够有效地保护高压电动机在起动瞬间受到大电流的冲击,降低起动电流,研究决定采用软起方式,增加一套高压软起动装置,通过高压软起动装置起动电动机。那么增加高压软起动装置是否就安全了吗？如果电动机没有正常起动,起动失败,那么将会产生持续的大电流,此时是否会造成电动机烧坏？下面针对这一问题进行分析。     

异步电动机软起动的数字仿真

异步电动机的软起动可控制电动机的起动电压和起动电流,减少电动机起动过程对电网和负载的冲击,同时保证电动机运行平稳。分析软起动的工作状态,并建立了数学模型。利用MATLAB软件对采用PI电流闭环控制的异步电动机软起动系统编制程序,通过实例进行仿真,并对仿真结果作了分析。     

异步电动机软起动的数字仿真

异步电动机的软起动可控制电动机的起动电压和起动电流,减少电动机起动过程对电网和负载的冲击,同时保证电动机运行平稳。分析软起动的工作状态,并建立了数学模型。利用MATLAB软件对采用PI电流闭环控制的异步电动机软起动系统编制程序,通过实例进行仿真,并对仿真结果作了分析。     

基于分级变频软起动器中功率因数角闭环控制的研究

研究了三相交流异步电动机分级变频起动的起动方法,并分析了电机在软起动调压过程中产生电流振荡的原因。提出了在电机分级变频软起动器控制系统中应实施电动机功率因数角闭环控制的观点,通过分析指出:晶闸管调压电路中可控的晶闸管触发角应该由两部分组成,一部分是按预定规律调整的角度,另一部分是跟随电机功率因数角的变化而增加的动态调整角度。该方法可以使电动机起动过程中的电磁转矩和电流脉动得到明显的抑制。     

磁阀式可控电抗器在高压电机软起动中的应用

在比较各种软起动方式后,给出一种新型磁控电机软起动方案,即在电动机定子回路中串入磁饱和可控电抗器来实现电机的软起动,保证电动机按负载要求的起动特性平滑起动,有效地降低对电网电压波动的影响。     

大功率异步电动机新型软起动装置的设计与实现

为了减小异步电动机起动过程中对电网的冲击、消除传统降压起动设备的有级触点控制对异步电动机的冲击、改善异步电动机的起动特性,基于电力电子技术对电动机软起动进行了研究。软起动装置是基于三相交流调压技术,通过改变晶闸管的触发角以调节定子两端的电压来实现的。采用双闭环控制的三相交流调压电路设计了50k W异步电动机软起动装置。内环电流控制及外环电压控制采用PI控制,实现了自动调节电动机起动电流,不但限制了电流,又使端电压平稳上升,实现了交流异步电动机平稳软起动。     

产品导购

DJR1系列数字软起动器 软起动功能 降低电动机的起动电流; 避免电动机起动时供电线路产生瞬间电压跌落,造成设备、仪表误动作; 防止起动时产生的力矩冲击,避免断轴或产品质量受损;     

EDSA在油田大功率异步电动机起动计算中的应用

本文通过研究油田中大功率异步电动机起动方式分析,不同起动方式对电动机本身、相邻设备、以及不同电压等级母线所造成的压降不同,利用EDSA仿真模拟电动机直接起动、软起动、变频起动三种起动方式,从理论和实际结果验证了选择软起动方式的必要性。     

Soft-started induction motor modeling and heating issues for different starting profiles using a flux linkage ABC frame of reference

In order to mitigate the adverse effects of starting torque transients and high inrush currents in induction motors, a popular method is to use electronically controlled soft-starting voltages utilizing series-connected silicon-controlled rectifiers (SCRs). Investigation of semioptimum soft-starting voltage profiles was implemented using a flux linkage ABC frame of reference model of a soft-started three-phase induction motor. A state-space model of the soft-starter thyristor switching sequence for the motor and load was developed and implemented in a time-domain simulation to examine winding heating and shaft stress issues for different starting profiles. Simulation results of line starts and soft starts were compared with measured data through which validation of the model was established. In this paper, different induction machine soft-start profiles are shown, and comparisons of starting times, torque profiles, and heating losses are made. Discussion of these results and conclusions as to the near-optimum types of profiles are delineated based on peak torque, starting times, and winding heating criteria.     

控制系统延迟对轴扭振的影响

控制系统中的轴扭振会引起系统控制量的振荡,加大机械传动装置磨损,甚至会导致传动轴断裂。在工业应用中,多采用陷波滤波器抑制轴扭振,而陷波频率的选取通常未考虑控制系统延迟因素。基于电机角速度增量、轴转矩增量和电机电磁转矩增量的相位图,分析了控制系统延迟对轴扭振频率的影响。仿真结果对分析结论给予了验证。     

Start-Up Torques in Synchronous Motor Drives

During run-up as an induction motor, the torque produced by a synchronous machine has oscillating components in addition to the natural frequencies of torsional oscillation of the complete drive system so that the shaft torque may differ substantially from the motor electromagnetic torque. The latter can be divided into four components: 1) a unidirectional or accelerating component, 2) an oscillating component due to magnetic saliency and nonuniform rotor windings, 3) oscillating components due to higher harmonics of air gap permeance and winding magnetomotive force, and 4) components caused by switching the supply. In addition, slot effects and magnetic saturation may also lead to oscillating torque components. The factors affecting the magnitude and frequency of these components are discussed and related to recordings of actual shaft torque.     

Combined electrical and mechanical model of electric submersiblepumps

The electric submersible pump unit consists of a pump powered by a medium-voltage three-phase induction motor. The power transmission system is integrated with the riser pipes. Starting the pump causes heavy dynamic stresses on the motor shaft and the mechanical connection between pump (impellers) and shaft. The motor and its load will generate transient torque pulsations that may be damaging to shaft and coupling, particularly to the key grooves. System models are developed to predict the electrical and mechanical conditions on starting. Different torsional models with certain types of nonlinearities, combined with different motor models have been examined to find combinations that give the best results. The motor models applied include saturation in the main flux path and the leakage flux paths, as well as rotor deep bar effect. It has been shown how the pump parameters, material coefficients, design dimensions, and number of impellers affect the dynamic stresses. The aim has been to optimize the design with respect to the transient stresses. The simulations reveal that the resulting shaft torque, caused by excitation from resonant frequencies during the acceleration period, amount to high values that may result in excessive overloading of shafts, couplings, and key grooves. Maximum torque is, as expected, strongly dependent on the shaft dimensions. Certain shaft diameters may cause resonance and, thereby, heavy torsional amplitudes. It has been shown how the model can be a tool in the struggle to find the optimum shaft diameter     

单支撑大型同步电动机轴系的设计

介绍了驱动往复式压缩机用单支撑电机轴系挠度和临界转速的相关计算,并给出了计算实例,同时对轴的强度计算做了简要介绍。由于该电动机的负载特性决定了在轴系设计时要综合考虑刚度和强度,同时应与压缩机轴系共同做扭振分析,保证整个轴系固有扭振频率避开强制振荡频率,避免发生共振,以确保电机运行可靠性,提高机组系统安全。     

汽轮发电机组轴系扭振的独立模态空间鲁棒控制

提出在汽轮发电机组轴系扭振的独立模态空间控制回路中，采用H∞扭振模态观测器估计模态反馈信号。证明了独立模态空间控制器町以独立设计，而引入H∞扭振模态观测器对闭环系统极点分布的影响可以忽略不计。基于H∞控制理论导出了针对受控扭振模态设计的独立模态空间控制器的鲁棒稳定条件。另外，出于实际考虑，建议扭振控制转矩以发电机电磁转矩分量的形式实现，而将慢变的机械转矩看作干扰，提出了抑制其影响的H∞性能指标。在此基础上提出轴系扭振的独立模态空间鲁棒控制，并归结为带有闭环极点配置约束的多目标H∞综合问题。算例仿真表明，轴系扭振独立模态空间鲁棒控制策略是可行的、有效的。     

A Microprocessor-Based Motor Speed Regulator Using Fast-Response State Observer for Reduction of Torsional Vibration

A new state observer, which is suitable for microprocessor-based motor drives, and its application to suppression control of shaft torsional vibration are described. A distinct feature of the state observer is that a fast-response load torque estimation is obtained by processing the detected motor current and the encoder output pulses by a hardware circuit for each encoder pulse generation. Suppression control of the shaft torsional vibration is achieved by calculating a compensation signal from the estimated load torque with the microprocessor software. A microprocessor-based speed regulator for dc motor drives, which utilizes the state observer and suppression control of the shaft torsional vibration, was developed for evaluation purposes and tested with a 15-kW dc motor. The load torque of the motor can be estimated accurately, even with a 15-Hz vibration frequency, and the torsional vibration can be eliminated with the proposed suppression control.     

Starting Characteristics of Electric Submergible Oil Well Pumps

The electric submergible pump (ESP) consists of a centrifugal pump powered by a medium-voltage three-phase induction motor. Being constrained to operate within common well casings, the ESP is rather unique; for example, a 500-hp motor may be less than 6 in in diameter and more than 100 ft long. As such, its mechanical rotational behavior under starting conditions can be severe, and some actions normally thought to attenuate the severity can actually amplify it. Both analytic and experimental approaches to understanding the starting incident and its effects are presented. A model was developed to predict the electrical and mechanical conditions prevalent when starting with various types of reduced-voltage fixed-frequency starters. These include the solid-state soft starter, reduced-voltage starters using variable or switched series impedances and stepped-voltage starters. Direct on-line full-voltage starting was used as a base case. Model predictions for the various starting methods were compared against tests measuring transient speed, voltage, current, and torque. Test results indicate that some starting techniques can produce unstable operation, i. e., torsional vibration. In large horsepower ESP's shaft strength safety factor is reduced due to space limitations and torsional vibrations must be minimized to avoid breakage due to fatigue. Depending on the application, configuration of the ESP and adequacy of available power, good motor starter design can be crucial to reliability. Finally, it is believed that this work has direct applicability to the starting of many more common large induction motors.