碳滑板电滑动温升及其对滑板磨损影响的试验研究

使用高速载流摩擦磨损试验机,研究了碳滑板与接触线电滑动摩擦时接触压力、相对滑动速度、电流和电弧放电能量变化对碳滑板温升的影响,比较了不同温升时碳滑板的磨损形貌.结果表明:滑板的温升随滑动速度、电流、电弧放电能量的增加而增加,随接触压力的增加而减小.碳滑板的磨损形貌观察显示:碳滑板的温升会显著影响滑板的磨损形貌,随着温升的增加,碳滑板的磨损就越严重.碳滑板的不同温升对应着不同的磨损机制:温升50℃左右时,碳滑板表面以片状剥离的机械磨损为主;温升90℃左右时,碳滑板表面以机械磨损为主,并出现少量的烧蚀区域;温升在180~200℃左右时,碳滑板表面出现大量的烧蚀区域,以电弧烧蚀磨损为主;温升在300℃左右时,碳滑板易出现疲劳裂纹,以电弧烧蚀磨损为主.     

数字化温湿度采集仪的研制

在日常生产活动中,很多场合需要进行温度、湿度测量。为了达到对温湿度的精确测量,设计并实现了一种数字化温湿度采集仪。该采集仪以89S52单片机为核心,具有温湿度采集范围广、精度高、抗干扰能力强、接口丰富、使用灵活等优点。采集仪既可以作为单机仪器,也可以通过RS485组成网络化测试系统。作为单机仪器时,有大屏幕的LCD(128*64)显示实时的温、湿度和露点温度。通过对现场试验测试并对结果进行分析,表明该采集仪完全满足测量要求,有较高的使用价值。     

Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage

Polyimide （PI） film is an important type of insulating material used in inverter-fed motors. Partial discharge （PD） under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage （BCSIV） is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage （PDIV）. The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy （FTIR） and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy （SEM）. The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond （C-O-C） and imide ring （C-N-C） on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant e to increase and dielectric loss tan ~ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI oolvmer bulk.