2 Engineering2.12 Loading conditions54 DS7 Soft starter 09/16 MN03901001Z-EN www.eaton.com2.12.3 Different overload currentIf load cycles or start frequencies are different, the following graphs can beused for reading the possible time current combination.The example shown here is a 30 kW motor (400 V, 55 A) with an assignedDS7-34xSX055… soft starter (55 A, rated operational current = motorcurrent). The maximum starting current of 165 A (I LRP) can be achieved for5 s at 10 starts per hour (overload factor X = 3).eThe prospective locked rotor current I LRP is the motor current that occurswhen the rated operating voltage is applied and the rotor is locked(I LRP = X x I e).Figure 35: Real (dashed) and normalized load current55A: AC-53a: 3 -5 : 75 - 10SF [%]Tx [s]XIe [A]F = 10/h, 1 h = 3600 s l T x + t B + t P = 360 sT x + t BF = x 100 % lT x + t B + t P5 s + 265 s x 100 % = 75 %5 s + 265 s + 90 sILRPX = l ILRP = X x Ie = 3 x 55 A = 165 AI eIeILRPITx t B t P1 htt P1 2 10TItI eI LRP
