| There are numerous electric contacts in electronics, electric-power and automatic control system. Their capability affects the reliability of electric and electronic devices directly. Therefore studying the effects of environmental factors on electric contact capability, including dust, air, electric field, temperature and humidity and so on, will improve the reliability of electric and electronic system.The deposition of dust particles on electric contact surfaces closely relates to the electric field which exists around the area. In order to evaluate the ability of electric circuit which attracts dust particles, a new criterion and method were introduced. A simulation using this criterion and method was carried out. The result indicates that electric connectors' ability to attract dust particles closely relates to the voltage and the distance between its two terminals. These relationships can be described by a quadratic polynomial independently. Otherwise, by studying the motion of dust particles placed in certain alternating electric field, it can be detected that their motion trend has no relationship with the polarity of charges which carried by them, but relates with when they appear in this electric field. All the conclusions above have been proved by preliminary experiment.Temperature and humidity are also very important factors which affect the electric contact reliability. The experiment box of dust deposition (EBDD) must possess the ability to control them. The EBDD system has the characteristics of large time delay and multi-variable coupling. Through establishing the mathematical model of EBDD can help analyzing its characteristics, and guide the design of the controller. An effective control of the EBDD will be carried out through designing an appropriate control strategy and fuzzy controller. Simulations indicate that the fuzzy controller is adaptable to the large-scale varying of system parameters. |
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