Emotron MSF 2.0 Softstarter

Current limitCurrent limit at start can be used together with all startmethods to limit the current to a defined max level whenstarting (150-500% of In). However, only a properly configuredtorque-controlled start will lead to linear acceleration.For this reason it is not recommended to set a current limitfor pump applications. Moreover, as the motor torque isproportional to the square of the current, setting a low currentlimit will limit the motor torque considerably. If thecurrent limit is set too low in relation to the application’srequirements, the motor will not be able to accelerate theload.The combination DOL start and current limit at start givesa start ramp with constant current. The softstarter will controlthe current up to the set current limit immediately atstart, and keep it there until the start is completed or the setstart-up time expires.Current limitFig. 41 Direct on-line start in combination with current limitat start.Current limit at start [314]In this menu the current limit at start is set.3 1 4CurrentFLCoF FStarting timeCurrent limit at startDefault: oFFRange: oFF, 150-500% of I noFFCurrent limit disabled.150-500 Current limit at start.TimeSettingNOTE: Even though the current limit can be set as low as150% of the nominal motor current value, this minimumvalue cannot be used generally. If the current limit is settoo low in relation to the application’s requirements, themotor will not be able to accelerate the load.If the starting time is exceeded and the softstarter is stilloperating at current limit, an alarm will be activated accordingto “Current limit start time expired” settings for motorprotection, menu [231]. Operation may be stopped or continuedwith a pre-defined voltage ramp. Note that the currentwill rise unchecked if the operation continues.Start time [315]In this menu the desired start time is set. This menu is notavailable if DOL is chosen as a start method and no currentlimit is configured.3 1 5Default: 10 sRange: 1-60 s1-60 Start time.Start timeTorque boostIn specific applications torque boost is required for the start.The torque boost parameter enables a high torque to beobtained by providing a high current for 0.1-2 seconds atstart. This enables a soft start of the motor even if the breakaway torque is high at start. For example in crushing millsapplications etc.When the torque boost function has finished, starting continuesaccording to the selected start method.Torque boostCurrent limitFLC10Torque boost active timeSettingFig. 42 The principle of the torque boost when starting themotor.TimeNOTE: Check that the nominal motor current isconfigured properly in menu [211] if the current limitfunctionality is used.Emotron AB 01-4135-01r2 Functional description 59