ВЛИЯНИЕ ПЕРЕХОДНОГО СОПРОТИВЛЕНИЯ НА ЭФФЕКТИВНОСТЬ ЭКРАНИРОВАНИЯ БОРТОВОЙ КАБЕЛЬНОЙ СЕТИ ЛЕТАТЕЛЬНЫХ АТМОСФЕРНЫХ И КОСМИЧЕСКИХ АППАРАТОВ

摘要

Рассмотрено влияние внешних факторов на эффективность экранирования бортовых кабелей летательных атмосферных и космических аппаратов. Приведены результаты исследований температурных и климатических воздействий на переходные сопротивления кабельных электрических соединителей. Представлены результаты испытаний эффективности экранирования при изменении переходных сопротивлений. Показана необходимость учета на этапе проектирования экранов бортовых кабелей влияния на их эффективность экранирования температурных и климатических факторов в течение жизненного цикла кабеля.%To ensure the specified shielding efficiency electromagnetic screen should be homogenous to the maximum. The uniformity of the shield depends on the resistance between the cable shield, the electrical connector and the onboard device case, i. e. transition resistances. High shielding efficiency can be ensured with small values of transition resistances. The transition resistance is not a constant and can variable significantly during the life cycle of a product. These variations are caused by the effect of various factors: shields and cases bonding and connecting techniques; temperature and environmental conditions; operating conditions. The results of the experiment that simulating a stay in a tropical climate revealed, that the magnitude of the transition resistance has increased up to 8 mOm, and in some cases it increased from 1 to 26 mOm, which significantly exceeds the standard value. While temperature fluctuations effect testing, cable connectors subjected to thermal shock by immersion in liquid nitrogen with subsequent heating to 290℃ by the stream of hot air. The results of this experiment demonstrate, that the transition resistance of the heated connector increases from 1 to 6 mOm. In all these experiments, significant changes of transition resistances values in the direction to increase without returning to the initial values were observed. The reason for this consists in the thermal deformation of the parts' shape and contact failure due to the emergence of the oxidized layer. The results of the shielding effectiveness study show that the magnitude of the transition resistance affects significantly the levels of induced interference voltage at the load, connected to the onboard instrument simulator cable. Transient resistance value increasing reduces the onboard cables shielding efficiency. Thus, while electromagnetic shields designing, it is necessary to account for in shielding efficiency decrease on exposure to thermal and climatic factors during the life cycle of the product.