3 Product description 3.1 Fields of application Soft starters are used to start three-phase induction motors with reduced torque and reduced starting current. SIRIUS soft starter family The SIEMENS SIRIUS soft starter family comprises three different versions with different functionalities and prices. 3RW30 and 3RW40 Simple or standard applications are covered by the SIRIUS 3RW30 and 3RW40 soft starters and are described in this manual. 3RW44 The SIRIUS 3RW44 soft starter is used if higher functionality is specified, e.g. communication over PROFIBUS or the availability of measuring and monitoring values, as well as for ultra- heavy-duty starting.
The SIRIUS 3RW44 soft starter is described in a separate system manual. Download from 3RW44 manual ( http://support.automation.siemens.com/WW/ llisapi.dll?func=cslib.csinfo&lang=de&objid=21772518&caller=view ). 3.2 Basic physical principles of a three-phase induction motor SIRIUS soft starters are used to reduce the current and torque of a three-phase induction motor during the startup process. 3.2.1 Three-phase induction motor Fields of application Three-phase induction motors are used in a wide range of applications in commerce, industry, and trade owing to their simple, robust design and their minimal maintenance.
Problem If a three-phase induction motor is started directly, its typical current and torque characteristics can cause disturbances in the supply system and the load machine. SIRIUS 3RW30 / 3RW40 Manual 01/2010, 535 1995-02 DS01 15