PRS－80（160）保护装置工作原理
参考答案：
当电源分断时，感性负载L两端产生较大自感电动势。如不接任何保护装置，此时产生的自感电动势对接触器触头及线路造成较大影响。PRS保护装置并接于感性负载L两端，PRS正端并接在感性负载L电流流入端，负端并接在感性负载L电流流出端。当电源分断时，感性负载L两端产生自感电动势，通过PRS中二极管V及熔体FU加以释放，从而达到抑制大容量感性负载L自感电动势产生的目的，减少机车电路中高压电磁干扰，延长直流接触器触头的使用寿命。PRS保护装置中熔体FU具有延时熔断特性，它的特点是能短时承受很大电流，而当线路长时间通过大电流时，熔体FU熔断，熔体熔断后，熔断指示器引线熔断，熔断指示器弹出。阻容RC具有过压保护的作用。
Nowadays fashion speaks aloud.Then do you choose what you wear or does the ____ choose it for you？I am one of the million Americans who struggle with ____ the new trends.The newspapers and magazines work their hardest in trying to ___ us to buy new things for home，work，and family.Many large ___ spend millions of dollars for a oneminute commercial on one of the ___ stations such as FOX and CBS.Television and magazines ____ carefully not only what to wear and when to wear it but also what others are wearing such as movie stars，____ and music artists.Television，one of the ___ mediums of the media world，talks with us about who is wearing what and what is fashionable for the ____.Television shows give us information on new trends ____ all different types of people and in all different countries.Designers such as Calvin Klein，Levi’s and many others try to ____ us to their cool commercials.Indeed，they get ____ from the commercials after their designs are sold. Television influences the way we ____.It searches each and every one of our wardrobes(衣橱) with telling us what is ____ and what is not.Teenagers，____，give a lot of their attention to these television programs.They even wish they could ____ like the models immediately.The commercials try to ____ the younger generation because they will have them in the palm of their hands for the ____ of their lives.Also teenagers are ____ influenced by television with the billions of dollars spent on advertisements.These advertisements have them ____ widely—they really know what teenagers like.
|