Siemens MICROMASTER 440 Operating Instructions Manual

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3 Functions Issue 10/03MICROMASTER 440 Operating Instructions160 6SE6400-5AW00-0BP03.20.1 Thermal motor modelThe data, required for the thermal motor model, is estimated from the rating platedata (refer to Fig. 3-21) entered during the quick commissioning (refer to Section3.5.2). This data permits reliable, stable operation for standard Siemens motors. Ifrequired, parameter changes must be made for motors from third-partymanufacturers. We always recommend that an automatic motor data identificationrun is made after quick commissioning so that the electrical equivalent circuitdiagram data can be determined. This allows a more precise calculation of thelosses which occur in the motor which has a positive impact on the accuracy of thethermal motor model.Example:A stator resistance, which is parameterized to be too high, would result, in themodel, to higher losses than in a real motor and an excessively high calculatedmotor temperature would be displayed.If changes are required in order to optimize the thermal model, then as a first step,the motor weight (P0344) should be checked for plausibility. Generally, the motorweight is taken from the Catalog data of the motor manufacturer. The thermalmodel can be further optimized by adapting the standard overtemperatures for thestator iron P0626, the stator winding P0627 and the rotor P0628. The standardovertemperatures represent the steady-state temperatures to be expected in ratedoperation with respect to the environment and are used to estimate the thermalresistances. Generally, these overtemperatures are not listed in the Catalog.The ambient temperature P0625 is another important parameter which influencesthe precision of the thermal model.3.20.2 Temperature sensorWhen the motor is operated below therated speed the cooling effect of theshaft-mounted fan is reduced. As aresult, for most motors when continuallyoperated at lower frequencies, thepower has to be reduced. Under theseconditions, motor protection againstoverheating can only be guaranteed ifeither a temperature sensor (PTC orKTY84 sensor) is integrated in themotor and is connected to the controlterminals 14 and 15 of theMICROMASTER 440 (refer to Fig. 3-70)or the motor temperature model wasdetermined (refer to Section 3.20.1).NOTEIn order to avoid EMC noise from being coupled-in to the drive converterelectronics – and the associated disturbances – it is not permissible to use freeconductors in the motor cable to connect the temperature sensor to the driveconverter.The temperature sensor must be connected to the drive converter using a separatecable (if at all possible, this cable should be shielded).PTC/KTY5 VKl. 14Kl. 15AD574 ΩFig. 3-70 Connecting a temperaturesensor to MICROMASTER