青海省农产品加工业的现状 问题及对策     

肖明 《农产品加工．学刊》2007,(4):52-55

简述了青海省农产品加工业的发展现状及存在问题,并提出了相应的发展对策,旨在加快青海省农产品加工业的发展,实现农产品转化增值,优化产业结构,吸纳农村富余劳动力,提高农业综合效益。  相似文献   

Harmonic Analysis and Suppression of High-frequency Welding Devices     

LUO Sheng-jin  DU Xiong  ZHOU Luo-wei 《保鲜与加工》2005,(2):26-31

This paper analyzes the structure and line current waveform of 3-phase AC voltage regulation circuit. As an application of 3-phase AC voltage regulation circuit, a high-frequency welding device's simulation model and harmonic analysis of line current are presented. Results of simulation are compared to field measurements. The two are in a good agreement, so this simulation model is correct. Two single-tuning filters and one second-order HPF are designed according to the device's harmonic condition. Simulation results of the circuit with filters indicate decrease of the harmonics in current of power supply, and the waveform is close to sinusoidal wave, which prove correctness of the solution to harmonics pollution.  相似文献   

Influence of HVDC System on the Shaft of Hydro-generator Unit     

XU Yuan-yuan  LIAO Yon  CHEN Guo-qing  XlANG Da-wei 《保鲜与加工》2006,(1):36-40

Widely concerns of the influence of the HVDC system on the Three Gorges power station have been shown so far. Based on the understanding of the mechanism of the non-characteristic harmonics introduced by HVDC system, the influence of interharmonics on the shaft of hydro-generator unit is studied. A MATLAB simulation model for the Three Gorges hybrid AC and DC transmission system with considering the effect of generator-unit shaft is established. Through time-domain simulation, the influence of the minor-associated component of interharmonics on the generator-unit shaft is analyzed, which arise from the asynchronous operation of the HVDC system. Also, the complex torque coefficient method in frequency-domain is used to analyze this problem. Same conclusions can be drawn from the results of timedomain and frequency-domain analyses.  相似文献   

STATE VARIABLE METHOD FOR DYNAMIC SIMULATION OF HVDC SYSTEMS     

Zhang Wei Ren Zhen Qin Yihong Liao Qing 《保鲜与加工》1990,(1):56-62

A flexible mathematical model used for dynamic simulation studies of HVDC systems which is based on the stale variable method is presented, and the correspongding computer program has been implemented. Generality, easy to use, and suitable to run on microcomputers are the main features of the model and the computer program. Therefore the model is easy to be extended for application. An example is given in the paper to verily the coneclness of the model and the program.  相似文献   

Improved Fuzzy Algorithm for Excavator''s Elevating Controlling System     

HAN Li  YI Jiang neng  ZHOU Xiao feng 《保鲜与加工》2001,(6):67-70

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Analysis and Comparison of Four Transposition Methods in the Stator Bar of Hydrogenerator     

GUO Ning  HAN Li  SHI Xiao-kun 《保鲜与加工》2007,(2):42-45

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Comparison of DC Pollution Flashover Performance of Various Types of Long String Insulators     

LUO Li-yun  JIANG Xing-liang  ZHANG Zhi-jin  HU Jian-lin  SUN Cai-xin 《保鲜与加工》2007,(7):42-45

With the development of EHV/UHV DC transmission projects, it is inevitable to study DC pollution flashover performance of long insulator strings. The DC artificial pollution tests of five types of porcelain and glass insulators have been carried out in the artificial climate chamber. The paper analyzes the relationship between 50% flashover voltage U50 and string length, the relationship between U50 and salt deposit density, flashover voltage gradients and valid creepage distances of DC polluted insulators. Based on the test results of insulator strings of 5 - 23 units, there are linear relationship between the 50% DC flashover voltages and string length. The experimental results show that the pollution flashover performances of various types of insulators are different, and that the pollution degree exponents of polluted insulators are affected ainsulator materials and shapes, whose values are 0.3 to 0.36. Under the same pollution degree, the pollution performances of glass insulators have advantage of those of porcelain insulators with the same configuration and the flashover voltage gradient along creepage distance and valid creepage distances of glass insulators are higher than those of porcelain insulators.  相似文献   

农村配电变压器反时限保护整定计算及调试     

李长捷  倪晶  王立舒 《农机化研究》2003,(2):223-224

农村配电变压器反时限保护的配合整定计算及速断、过流调试是保证保护装置具有选择性、速动性、灵敏性和可靠性必不可少的组成部分，每个过程都对保障电力安全运行起着举足轻重的作用。为此，就哈尔滨市郊区江洋轧钢厂变压器反时限保护与卫星变新农线出口定时限保护配合整定及调试进行简要分析。  相似文献   

旋风分离器在饲草干燥设备中的应用     

马文杰  刘德旺  王峰 《农机化研究》2006,(8):186-188

饲草干燥设备中的旋风分离器与普通旋风分离器从结构上有很多不同点,从而使其各部分参数以及饲草颗粒的运动轨迹有很大不同。为此,根据旋风分离器的工作原理,分析了饲草干燥设备中的旋风分离器各个部分的参数,并从理论上给出了饲草在旋风分离器中的运动轨迹,为旋风分离器在饲草干燥设备中的应用提供理论依据。  相似文献   

泵站微机数据采集系统接地问题的探讨     

陈虹  刘敏华 《中国农村水利水电》1997,(1):15-17

由于泵站内干扰源众多、设备复杂、干扰频率范围宽．为使泵站微机数据采集系统可靠运行，必须采取防干扰或抑制措施。系统地描述了泵站微机数据采集系统的接地要求．提出增强系统抗干扰能力和电磁兼容性的实施方案．归纳出具体施工过程中切实可行的接地措施。  相似文献