S5 Thermal Model469Motor Management RelaySetpointshttp://www.GEindustrial.com/multilin5–36 GE MultilinIf the motor starting current begins to infringe on the thermal damage curves, itmay become necessary to use a custom curve to tailor the motor protection so thatsuccessful starting may occur without compromising protection. Furthermore, thecharacteristics of the starting thermal damage curve (locked rotor and acceleration)and the running thermal damage curves may not fit together very smoothly. In thisinstance, a custom curve may be necessary to tailor motor protection to the motorthermal limits so it may be started successfully and be utilized to its full potentialwithout compromising protection. The distinct parts of the thermal limit curves nowbecome more critical. For these conditions, it is recommended that the 469 customcurve thermal model be used. The custom overload curve feature allows the user toprogram their own curve by entering trip times for 30 pre-determined currentlevels.As seen in the figure below, if the running overload thermal limit curve weresmoothed into one curve with the locked rotor overload curve, the motor could notstart at 80% line voltage. A custom curve is required.MESSAGE TIME TO TRIP AT6.50 x FLA: 8.5 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT7.00 x FLA: 7.3 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT7.50 x FLA: 6.3 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT8.00 x FLA: 5.6 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT10.0 x FLA: 5.6 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT15.0 x FLA: 5.6 sRange: 0.5 to 99999.9 s in steps of 0.1MESSAGE TIME TO TRIP AT20.0 x FLA: 5.6 sRange: 0.5 to 99999.9 s in steps of 0.1
