Emotron MSF 2.0 Softstarter

Some applications like conveyors or screws may need an initialtorque boost. However, for many applications it can beseen that the torque needed is much lower than the torquedelivered by the induction motor in a DOL start.A common method to reduce both starting torque and currentis to decrease the motor voltage during starting. Thefollowing figure shows how the motor’s torque and currentcharacteristics are changed when the supply voltage isreduced.This relationship is the base for any starting method usingreduced voltage. It can be seen that the possibility of reducingthe starting current depends on the correlation betweenthe motor’s and the load’s torque characteristic. For the combinationof an application with very low starting load and amotor with very high starting torque, the starting currentmay be reduced significantly by means of decreasing thevoltage during start. However, for applications with highstarting load it may – depending on the actual motor – notbe possible to reduce the starting current at all.T/T n 2,521,510,50TorqueU nU 2