THERMAL DEMAGNETIZATION AND RANDOMNESS OF DOMAIN NUCLEATION OF SINGLE PHASE Nd_2 Fe_(14) B

Based on the observation of temperature variation of both domain structure and magnetic con-trast.the thermal demagnetization and randomness of domain nucleation was discussed.     

基于解析法的永磁游标电机退磁分析

本文研究了三种不同退磁方式对永磁游标电机的电磁性能的影响,建立了永磁游标电机的退磁解析模型。该解析模型建立在精确保角映射的基础上,能准确地反映永磁游标电机的有槽气隙与无槽气隙之间的关系,从而准确计算磁场分布。针对永磁游标电机的退磁分析中存在的问题,提出了退磁电流与退磁永磁体之间的等效变换,在此基础上通过完全保角映射后得到准确的退磁磁场分布。最后采用有限元分析验证了永磁游标电机退磁解析模型。     

大负载惯量下无刷直流电机快速退磁制动研究

为在大负载惯量条件下获得更优的无刷直流电机制动效果,提出一种新颖的快速退磁制动方法。基于在浮相绕组上施加最大反向电压可以实现快速退磁的原理,设计出快速退磁制动时上下桥臂功率管的导通时序和PWM信号的施加位置。直接和间接实验结果皆验证了快速退磁制动方法的有效性,并将其与电机自由停止、能耗制动的制动效果进行了对比研究,对比实验结果表明所提出的快速退磁制动方法的优越性。     

一种轴向风冷结构对高速永磁电机转子温升的抑制研究

在变频器驱动方式下,高速永磁电机具有较大的转子涡流损耗,由于其转子的散热能力较差,易使永磁体温升较高,而发生不可逆失磁现象。采用机壳水冷结构可以有效地带走电机定子侧的热量,但是对于高速永磁电机的转子部位,水冷结构的冷却效果有限。以一台15 kW、30 000 r/min的高速永磁电机为例,设计了一种风、水混合冷却结构,基于流固耦合的计算方法分析了水速、风向以及不同风道截面积对电机永磁体部位温升的影响,并得出了相对的最优值。与仅采用水冷结构相比,增加该风冷结构可使永磁体温升降低了18.1 K,该结构可对大功率高速永磁电机的冷却系统设计提供一定的参考。     

永磁材料磁性参数的测量

主要介绍永磁材料磁性参数测试装置及测量方法。     

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.     

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.     

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.     

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.     

玻璃包覆钴基非晶丝巨磁阻抗的长度效应

通过测量长度不同的玻璃包覆钴基非晶丝在频率为100kHz时的GMI值,近似计算出玻璃包覆钴基非晶丝的圆周磁导率.玻璃包覆钴基非晶丝圆周磁导率下降随着长度增加而变得剧烈,导致GMI变化更剧烈.利用玻璃包覆钴基非晶丝的磁畴模型,分析不同长度时玻璃包覆钴基非晶丝的磁化过程,合理解释了GMI效应随玻璃包覆钴基非晶丝长度增加而明显的现象.