Product description 3.3 Functional principle of the SIRIUS 3RW30 and 3RW40 soft starters Note If wye-delta starters are exchanged for soft starters in an existing system, you should check the fuse ratings in the feeder in order to avoid false tripping. This is particularly important in connection with heavy-duty starting or if the fuse that is installed has already been operated close to the thermal tripping limit with the wye-delta assembly. All elements of the main circuit (such as fuses, motor starter protectors, and switching devices) must be dimensioned for direct starting and according to the on-site short-circuit conditions, and ordered separately.
For recommended fuse and motor starter protector ratings for the feeder with soft starter, refer to chapter Technical data [Page 121]. 3.3.3 Applications and use Applications and selection criteria The SIRIUS 3RW30 and 3RW40 soft starters represent a good alternative to direct or wye- delta starters. The most important advantages are: • Soft start • Soft stop (3RW40 only) • Simple installation and commissioning • Uninterrupted switching without current peaks that place a heavy load on the system • Compact, space-saving design Applications The typical applications include:
• Conveyor belts • Roller conveyors • Compressors • Fans • Pumps • Hydraulic pumps • Agitators • Circular saws / band saws SIRIUS 3RW30 / 3RW40 22 Manual, 01/2010, 535 1995-02 DS01