Soft start of several large squirrel cage motors with one frequency convertor

In the LD plant number 2 of Hoogovens IJmuiden, Netherlands, iron is transformed into steel by means of 3 convertors. During this process large quantities of gas and dust are being produced, which have to be exhausted by using fans. The authors discuss the problems of switching of squirrel cage motor driven exhaust fans. The solution is to use a frequency converter for each motor, however this requires an unacceptably high investment. To solve this problem one converter can be used with soft-start equipment. The authors discuss the construction and components of such an installation