Functions
8.22 Thermal motor protection and overload responses
Control Units CU240S
8-152 Operating Instructions, 11/2006, A5E00766042B AA
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 Extract from IEC85 thermal classes
Thermal Class Max. permissible temperature
Y 90 ｺC
A 105 ｺC
E 120 ｺC
B 130 ｺC
F 155 ｺC
H 180 ｺC
For the temperature model or the KTY84 sensor, the appropriate value Ï‘
warn
must be
calculated and entered into parameter P0604 (temperature warning threshold, default:
130ï½°C). The following applies:

WULS

ZDUQ
3
˽
˽
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.
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