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王功胜 《机械工人(冷加工)》2004,(8):74-77
电阻器的替代 电阻器可分为固定电阻器和可变电阻器。在习惯上,将固定电阻器称作电阻,将可变电阻器称作电位器。电阻器的标志应包括型号、额定功率、标称阻值、允许偏差、温度系数、噪声电动势及制造日期等内容。在数字电路中,除振荡、定时、分压等电路外,对阻值的要求 相似文献
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通过热变电阻器起动,达到降低起动压降,满足电机起动要求。对高压水泵起动及运行方式进行了研究,应用7SJ62综保装置,设置适合的联锁逻辑和控制方案,并在综保装置中组态应用,实现起动柜和运行柜的正常切换及保护配合。 相似文献
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《仪表技术与传感器》1975,(4)
在毛主席革命路线指引下,在批林批孔运动的推动下,武汉市无线电线材厂广大革命职工,发扬“独立自主,自力更生”的精神,试制成功VYJ型金属氧化物压敏电阻器(亦称非线性电阻器)。 相似文献
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本文对变电站10kV线路中性点接地做了分析与比较,指出了当前的几种常用接地方式存在的问题,结合现有的中性点灵活接地方式提出了中性点新型灵活接地方式的研究方向,该方式下中性点接地设备由消弧线圈和灵活投切的接地电阻器及选线电阻并联而成,充分发挥消弧线圈补偿电容电流、提高单相接地故障自恢复概率的作用,以及电阻抑制弧光接地过电压和谐振过电压的作用,并通过投入电阻器产生足够的电流使在单相永久接地故障下实现可靠的变电所选线。经过对Matlab仿真结果的理论分析,验证新型中性点灵活接地方式的优势。 相似文献
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以压敏电阻器为核心,可设计出简单可靠的多种相序测量(指示、显示)、报警和保护装置,本文介绍压敏电阻器用做相序传感器的原理,以及各类实验电路. 相似文献
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为研究大功率固态功率管的传热问题,文中以某风冷固态功率管为例,介绍了其结构形式,分析了从功率管管壳到空气热沉之间的主要热阻,通过热设计软件进行了仿真计算。计算结果表明,造成功率管温升较大的热阻有对流换热热阻、导热热阻和接触热阻。为了降低功率管的结温,对每个热阻分别进行了优化设计和计算,通过试验对优化后的模型进行了验证,测试结果与仿真结果一致。最后还对大功率固态功率管的热设计优化方法进行了介绍。 相似文献
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Kralik T Hanzelka P Musilova V Srnka A Zobac M 《The Review of scientific instruments》2011,82(5):055106
For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10(0) to 10(3) μm. The heat transferred from the hot (10 - 100 K) to the cold sample (~5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within ~2 nW∕cm(2) and ~30 μW∕cm(2) is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer. 相似文献
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A new high-level noise source was developed specifically for the calibration of Johnson noise power thermometers (JNPT), but it is useful in other applications requiring a stable, wideband, well-defined noise power spectral density. The design concept for the noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of an inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise of a 100-Omega resistor at a temperature of about 64 000 K. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 dB) in the frequency range 1-150 kHz which brackets typical passbands of the signal-processing channels of JNPTs. The noise source was evaluated by comparing its output noise power with the thermal noise power generated by a platinum resistor of known ohmic value at the temperature of the aluminum freezing point (933.52 K). The measured noise power was within 0.06% of the value computed from the fundamental thermal noise equation of Nyquist. The power spectral density varies less than 0.03% for ambient temperature fluctuations in the range 15 degrees -35 degrees C. 相似文献
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