In this paper We analysed the unloading performance feature of the multiple track combination tumbler switch which is always used in the engineering and introduced simply the designing method of the unloading valve which is widely used in the engineering .

分析了工程上常用的多路组合 换向 阀卸荷性能特点，并扼要地介绍了工程上广泛应用的卸荷阀设计方法。

Using Auto Tumbler Switch ( ATS ) controlled by PLC this system can operate in more different modes .

PLC自身 具备 可靠性、 灵活性、易操作性的特点，利用PLC控制 转换 开关（ ATS）可实现 交流所用 电系统的多种运行功能。