Thermal Motor Model - Siemens SINAMICS G120 Operating Instructions Manual

Functions
8.22 Thermal motor protection and overload responses
Temperature rise classes
In motor technology, temperature rise issues play a decisive role when dimensioning
electrical machinery. Different temperature limits apply for the various materials used in
electric motors. Depending on the insulating material being used, a differentiation is made
according to thermal classes (refer to the motor rating plate) with defined limit temperatures.
An excerpt from IEC85 is provided in the table below
Table 8-32
Thermal Class
Y
A
E
B
F
H
For the temperature model or the KTY84 sensor, the appropriate value ϑ
calculated and entered into parameter P0604 (temperature warning threshold, default:
130ｰC). The following applies:
8.22.1

Thermal motor model

Description
The data, required for the thermal motor model, is estimated from the rating plate data
entered during the quick commissioning. This data permits reliable, stable operation for
standard Siemens motors. If required, parameter changes must be made for motors from
third-party manufacturers. We always recommend that an automatic motor data identification
run is made after quick commissioning so that the electrical equivalent circuit diagram data
can be determined. This allows a more precise calculation of the losses which occur in the
motor which has an impact on the accuracy of the thermal motor model.
Example
A stator resistance, which is parameterized to be too high, would result, in the model, higher
losses than in a real motor and an excessively high calculated motor 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 motor weight is taken from
the Catalog data of the motor manufacturer. The thermal model can be further optimized by
adapting the standard overtemperatures for the stator iron P0626, the stator winding P0627
and the rotor P0628. The standard overtemperatures represent the steady-state
temperatures to be expected in rated operation with respect to the environment and are used
to estimate the thermal resistances. Generally, these overtemperatures are not listed in the
Catalog.
8-152
Extract from IEC85 thermal classes
Max. permissible temperature
90 ｺC
105 ｺC
120 ｺC
130 ｺC
155 ｺC
180 ｺC
Operating Instructions, 11/2006, A5E00766042B AA
must be
warn
Control Units CU240S