... size, light weight, featured series, good components interchangeability, perfect protection system, high technical economy standard, convenient maintenance and usage. The technical ... W4; W1,W2,W3,W4 is just used for frame level 1,2 and 3. and short circuit release is ... Altitude of installating site not exceeding 2000 meters above sea level.2.3 Atmospheric condition:Relative humidity not higher than ...