基于分形维数的PMSM局部退磁故障诊断

为了实现永磁同步电机(PMSM)永磁体局部退磁故障诊断,首先建立计及永磁体局部退磁故障的PMSM数学模型,实现永磁体局部退磁故障电气特性的定性与定量描述。在此基础上,提出了集成自适应基波提取和经验模态分解(EMD)于一体,基于分形维数的永磁体局部退磁故障诊断方法。最后,通过PMSM驱动系统稳态和动态运行工况对所提出的永磁体局部退磁故障诊断方法进行仿真测试和实验验证,综合系统仿真和实验验证结果证实了该方法的可行性和有效性。     

Thermodynamic performance of the 3-stage ADR for the Astro-H Soft-X-ray Spectrometer instrument

The Soft X-ray Spectrometer (SXS) instrument (Mitsuda et al., 2010) [1] on Astro-H (Takahashi et al., 2010) [2] will use a 3-stage ADR (Shirron et al., 2012) to cool the microcalorimeter array to 50 mK. In the primary operating mode, two stages of the ADR cool the detectors using superfluid helium at ⩽1.20 K as the heat sink (Fujimoto et al., 2010). In the secondary mode, which is activated when the liquid helium is depleted, the ADR uses a 4.5 K Joule–Thomson cooler as its heat sink. In this mode, all three stages operate together to continuously cool the (empty) helium tank and single-shot cool the detectors. The flight instrument – dewar, ADR, detectors and electronics – were integrated in 2014 and have since undergone extensive performance testing. This paper presents a thermodynamic analysis of the ADR’s operation, including cooling capacity, heat rejection to the heat sinks, and various measures of efficiency.     

基于特高压交流变电站检修典型问题分析

本文在对于特高压交流变电站检修典型问题演技中,主要对于轮停检修感应电压问题及测量误差等问题进行分析,希望能够为其他特高压交流变电站检修工作提供一定帮助.     

SAFARI engineering model 50 mK cooler

SAFARI is an infrared instrument developed by a European based consortium to be flown in SPICA, a Japanese led mission. The SAFARI detectors are transition edge sensors (TES) and require temperatures down to 50 mK for their operation. For that purpose we have developed a hybrid architecture based on the combination of a 300 mK sorption stage and a small adiabatic demagnetization stage. An engineering model has been designed to provide net heat lifts of 0.4 and 14 μW respectively at 50 and 300 mK, with an overall cycle duration of 48 h and a duty cycle objective of over 75%. The cooler is self-contained, fits in a volume of 156 × 312 × 182 mm and is expected to weigh 5.1 kg. It has been designed to withstand static loads of 120 g and a random vibration level of 21 g RMS.     

Operating modes and cooling capabilities of the 3-stage ADR developed for the Soft-X-ray Spectrometer instrument on Astro-H

A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule–Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes.     

钕铁硼磁体磁性的近似普适规律的研究

为了探讨钕铁硼磁体磁性的近似普适规律,把不同性能钕铁硼磁体在各温度下的退磁曲线加以归一化,这使退磁曲线显示出近似的普适性,而且其内禀矫顽力及剩磁随温度变化的规律也相似,据此导出钕铁硼磁体在各温度下退磁曲线的近似普适数学表达式,由该公式计算得到的各温度下的退磁曲线与实测曲线基本吻合.     

低温技术在太空监测领域的应用

随着低温技术的发展,制冷机的各方面工作性能显著改进,低温技术在航天领域得到了广泛应用。介绍了低温技术在国外太空监测卫星中的应用情况,分析其发展趋势。对太空监测所需要不同温度区间的制冷方法进行了总结,最后以国外执行监测任务卫星上的制冷系统为例说明制冷系统设计过程。     

一种具有抑制匝间短路失磁能力的永磁同步发电机

绕组匝间短路故障是永磁同步发电机(PMSG)最为常见的故障之一,容易造成永磁体的不可逆失磁。为了解决失磁问题,提出了一种具有抑制匝间短路下不可逆失磁能力的特种PMSG。首先介绍了发电机的特殊结构,紧接着通过数学模型推导出抑制失磁的原理。利用Flux软件建立发电机的模型,对发电机在运行过程中突然发生的匝间短路故障进行仿真。以永磁体各点在短路过程中出现的最小磁密值是否低于相应温度下退磁曲线的膝点磁密值为判断依据,分析得到发电机在不同短路故障下永磁体的失磁情况,从而验证了抑制失磁的可行性。     

异步起动永磁同步电机非正常工况退磁分析

为了研究异步起动永磁同步电机非正常工况运行时的退磁磁场对永磁体的影响,通过建立有限元模型,计算分析了包括三相突然短路、缺相运行、过载运行、降电压运行、失步运行和堵转运行6种常见非正常工况运行时定子电流、转速和永磁体工作点磁密的变化。结果表明,起动过程电流均大于非正常工况运行时的冲击电流,直接影响了作用在永磁体上的去磁磁动势,定、转子合成磁动势作用在永磁体上,将使得永磁体工作点磁密最小,退磁风险最大。当电机在同步状态运行时,永磁体工作点磁密为恒定的值;当电机在失步状态运行时,转子导条产生感应电流,定子电流和转子导条电流产生的合成磁场使永磁体工作点磁密做周期性波动。     

变频空调用无稀土磁阻电机的退磁仿真及验证

在以往的变频空调中,压缩机电机常采用高效节能的稀土永磁同步电机,但稀土价格的上涨使其在空调中的继续应用受到限制。无稀土磁材的永磁辅助式同步磁阻电机（无稀土磁阻电机）成本低廉,性能可与稀土永磁同步电机相媲美,在空调上具有很好的应用前景,但因无稀土磁材磁性能较弱,电机抗退磁能力较差而难以系列化生产。本文借助Ansoft软件对无稀土磁阻电机的退磁情况进行仿真,并与等效磁路法计算结果及实测结果进行对比。结果表明,采用三维瞬态场的动态退磁仿真结果与实测值很接近,该仿真方法能够很好地反映电机实际的抗退磁能力,在缩短开发周期、降低开发成本方面效果显著。