共查询到20条相似文献,搜索用时 703 毫秒
1.
一、长虹2938FD型彩电故障1:开机呈"三无"。电源供电电路中R802开路。更换R802;电源负载电路中C826不良。更换C8260。故障2:有伴音,无光栅。电源电路中C251漏电。更换C251。 相似文献
2.
鼠标
表面采用钢琴烤漆处理的鼠标,采用了右手人体工学设计,使得整体握感舒适,长时间使用也不会感到疲劳。而且。鼠标按键点击顺畅、回弹有力,声音清脆。不过。跟键盘一样,做工细节方面有待提升。标签方面出现褶皱。这确实不应该。 相似文献
3.
4.
5.
故障现象:图像效果差。出现此类故障时,首先打开画中画功能,观察图像是否显示正常。若异常,则检测VT电压是否正常。若无VT电压,则检查D1是否损坏。若D1正常,则检查高频头各脚电压是否正常。若电压正常,则检查高频头本身是否损坏。实际检修中,因高频头本身损坏而引起此类故障较常见。荨 相似文献
6.
<正>近日,我去上海新国际展览中心参观一个展览。正赶上那天下雨,我却要步行到展览中心西门外的酒店参加一个会。雨下得很大,所以一出西门,我就进了位于地下的嘉里商城,希望找家店买把雨伞。一进商城,我就看到在右侧一家店的橱窗里,十几把雨伞插在伞筒里。"买把伞。"我说。"不好意思,伞不卖。但是,可以借给您。"店里的服务员说。"怎么借?要押金还是要押证件?" 相似文献
7.
8.
9.
10.
11.
反映综合负荷动特性机理的感应电动机模型 总被引:11,自引:3,他引:11
针对感应电动机(IM)动态负荷模型(IM_DLM)不足以描述综合负荷特性,因而不实用的问题,采用解 耦辨识的方法分析了综合负荷有功功率特性和无功功率特性所对应的IM_DLM的不同;提出了在IM_DLM中引入一个无功功率“静态补偿”(LSVC)项的新模型 (LSVC_IM_DLM),并对引入的LSVC项的物理机理进行了定性分析。通过比较河北于庄和广东郭塘2个变电站的不同类型负荷特性对IM_DLM和LSVC_IM_DLM的辨 识结果,表明LSVC_IM_DLM较符合综合负荷的物理机理,其模型参数分散性小,LSVC项系数能反映不同负荷类型的变化,是一种具有重要实用价值的机理 型动态负荷模型。 相似文献
12.
《Electric Power Systems Research》2001,59(1):1-11
In recent years, passivity based control (PBC) scheme has gained wide attention among various nonlinear control methods. Based on Euler–Lagrange equations of motion, controllers are designed from an energy point of view. In this paper, the PBC is applied to induction motor (IM) speed drives with voltage-fed and current-fed inverters, respectively. The stability of the overall system for the voltage-fed IM drive has been verified rigorously, but it lacks for the current-fed IM drive. However, the controller structure of the latter is simpler than that of the former. Experimental results show that the PBC scheme is successful in speed control application for both IM drives. There is no significant differences between two IM drives. The overall system exhibits good robust performances in presence of motor parameter variations and load disturbances. 相似文献
13.
本文提出用电压型IGBT逆顺供电的异步电机静态参数的离散MRAS辨识方法。根据异步电机静态参模型,以定子电流的参考输出导出了参数适应律,并在仿真研究的基础上讨论了基于离散MRAS的异步电机静态参数辨训的DSP(TMS320C50)实现方法。通过仿真和实验证实了该方法对异步电机静态参数有较好的辨识精度和噪声适应性。 相似文献
14.
15.
微网中含大量高度非线性的感应电动机负荷,对微网孤岛运行时的电压稳定性构成严重威胁。为此,针对含多感应电动机负荷的微网,根据电力系统功率平衡的原则,从理论上推导了微网各电动机负荷转差与系统电压的动态耦合关系,进而说明感应电动机负荷更加敏感的原因及多感应电动机负荷的转差和系统电压之间的动态耦合特性与微网稳定性相关。基于MATLAB/Simulink仿真平台,搭建了风光柴储多源主从控制微网,通过仿真研究了不同条件下多机叠加启动及微网故障两种情况下微网的电压稳定性,进而提出了提高含多感应电动机负荷的微网电压稳定性的措施。仿真结果表明,多感应电动机负荷之间的相互作用对微网电压稳定性具有重大影响,且串联主从微网的临界故障清除时间受三相短路故障点离感应电动机负荷点的距离和故障点离主控单元的距离双重制约,采用叠加启动策略和故障点快速切机等措施可有效提高微网电压稳定性。所得结论为含多感应电动机负荷的微网稳定性研究与控制提供了理论参考。 相似文献
16.
Godpromesse Kenn Tarek Ahmed-Ali F. Lamnabhi-Lagarrigue Amir Arzand 《Electric Power Systems Research》2008,78(11):1881-1888
In this paper, an algorithm for time-varying parameter estimation for a large class of nonlinear systems is presented. The proof of the convergence of the estimates to their true values is achieved using Lyapunov theories and does not require that the classical persistent excitation condition be satisfied by the input signal. Since the induction motor (IM) is widely used in several industrial sectors, the algorithm developed is potentially useful for adjusting the controller parameters of variable speed drives. The method proposed is simple and easily implementable in real-time. The application of this approach to on-line estimation of the rotor resistance of IM shows a rapidly converging estimate in spite of measurement noise, discretization effects, parameter uncertainties (e.g. inaccuracies on motor inductance values) and modeling inaccuracies. The robustness analysis for this IM application also revealed that the proposed scheme is insensitive to the stator resistance variations within a wide range. The merits of the proposed algorithm in the case of on-line time-varying rotor resistance estimation are demonstrated via experimental results in various operating conditions of the induction motor. The experimental results obtained demonstrate that the application of the proposed algorithm to update on-line the parameters of an adaptive controller (e.g. IM and synchronous machines adaptive control) can improve the efficiency of the industrial process. The other interesting features of the proposed method include fault detection/estimation and adaptive control of IM and synchronous machines. 相似文献
17.
18.
19.
20.
矢量变换后异步电动机数学模型中还存在M轴和T轴间的交叉电势的耦合作用,影响调速系统的控制性能.分析了目前主要的交叉耦合电势解耦方法及解耦控制原理和特点,重点讨论了源于化工过程控制的内模解耦方法.该方法具有对模型精度要求低、电机参数变化基本不影响解耦效果的特点,是一种值得推广的解耦新方法. 相似文献