Toshiba GR-200-5 Instruction Manual

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6F2T0207 (0.01)GRE200 (5,6)- 328 -wheret time to operate for a constant overload current of I (minutes)I motor current (amperes)IAOL allowable overload current (amperes) of the stator, defined by the setting[Mot-THM]Ip the pre-motor current (amperes)τs thermal time constant (minutes), defined by the setting [T-Mot-THM]Ln natural logarithmIn Equation (2.28-5), cold curves are special versions of the hot curves where Ip is zero, cateringfor the situation where a cold system is switched onto an immediate overload.Figure 2.28-8.a shows the cold state where an overload has been switched onto a previouslyun-loaded system. Figure 2.28-8.b shows the hot state where an overload is switched onto asystem that has previously been loaded to 90% of its capacity. The figures are in conformitywith the IEC 60255-149 curves, and these curves are drawn in a range of settings of the timeconstant (s).a.Thermal Curves (Cold Curve - no prior load) b. Thermal Curves (Hot Curve - 90% prior load))10050201051Figure 2.28-8 Thermal curvesWhen the motor status is stop status, the stator thermal state can be shown by Equation(2.28-7):