variable frequency and speed

• 变频调速

variable frequency and speed的用法和样例：

例句

1. The paper introduces the method and effect of boiler fa.
   文章介绍了锅炉引风机采用变频调速实现炉膛负压自动调节的方法以及在工业运行中的效果。
2. The maturing of variable frequency technology becomes an assurance for the reliable operation of a trolley type scraper.
   变频调速技术的成熟是滑线式铲运机可靠工作的保证。