Product description 3.3 Functional principle of the SIRIUS 3RW30 and 3RW40 soft starters Example SIEMENS 1LG4253AA motor (55 kW) Rated data at 400 V P e : 55 kW I e : 100 A I direct starting : Approx. 700 A M e : 355 Nm ; e.g.: M e = 9.55 x 55 kW x PLQ n e : 1480 rpm M direct starting : Approx. 700 Nm Set starting voltage: 50 % (Ѕ of mains voltage) => I starting Ѕ of direct starting current (approx. 350 A) => M starting ј of direct starting torque (approx. 175 Nm) The diagrams below show the starting current and torque characteristics for a three-phase induction motor in combination with a soft starter:
0RWRUFXUUHQW , , 'LUHFW RQOLQH VWDUWLQJ , 6RIWVWDUWHU , 1RP 1RP 0RWRUVSHHG Q Figure 3-3 Reduced current characteristic of a three-phase induction motor during starting with a SIRIUS 3RW30 or 3RW40 soft starter SIRIUS 3RW30 / 3RW40 18 Manual, 01/2010, 535 1995-02 DS01