Siemens SINAMICS PERFECT HARMONY GH180 Function Manual page 197

For these options, the overload pending and overload settings represent the motor temperature
limits, in percent of rated motor temperature, at which the overload warning and trip are
generated.
Note
Use proper values for motors outside of NEMA table
To work properly for motors outside of the NEMA table, the "Maimum Motor Inertia" (ID 1159)
parameter must contain the proper value. Otherwise use the legacy thermal overload function.
Description of the Motor Thermal Model
The motor thermal model estimates motor temperature based on the net heat generated in the
motor and its thermal mass as depicted in figure Motor Thermal Model .
Note
Possible consequences of adjusting parameters
Since this is a thermal model, the parameters for establishing the overload pending alarm
(1139) and Overload (1140) levels are in PU temperature and as such do not increase rapidly.
Therefore these parameters should not be adjusted from default unless absolutely necessary,
and only with a full understanding of the impact. Raising them could result in defeating motor
protection.
Figure 7-10
The motor thermal model estimates the heat generated in the motor from the following values:
• stator voltages
• stator currents
• motor parameters.
The motor thermal model makes an estimate of the heat transferred from the motor, due to
motor cooling, from the allowable motor current.
The motor loss calculation also includes the losses generated with dual-frequency braking
(DFB). The thermal mass of the motor, or its heat capacity, shown as M
NXGPro+ Control Manual
Operating Manual, A5E50491925A
Motor Thermal Model
Operating the Control
7.7 Motor Thermal Overload Protection
is determined from the
TH,
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