Thermal Motor Model; Temperature Sensor - Siemens MICROMASTER 440 Operating Instructions Manual

3 Functions
3.20.1

Thermal motor model

The data, required for the thermal motor model, is estimated from the rating plate
data (refer to Fig. 3-21) entered during the quick commissioning (refer to Section
3.5.2). 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 a positive 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, to 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.
The ambient temperature P0625 is another important parameter which influences
the precision of the thermal model.
3.20.2

Temperature sensor

When the motor is operated below the
rated speed the cooling effect of the
shaft-mounted fan is reduced. As a
result, for most motors when continually
operated at lower frequencies, the
power has to be reduced. Under these
conditions, motor protection against
overheating can only be guaranteed if
either a temperature sensor (PTC or
KTY84 sensor) is integrated in the
motor and is connected to the control
terminals 14 and 15 of the
MICROMASTER 440 (refer to Fig. 3-70)
or the motor temperature model was
determined (refer to Section 3.20.1).
NOTE
In order to avoid EMC noise from being coupled-in to the drive converter
electronics – and the associated disturbances – it is not permissible to use free
conductors in the motor cable to connect the temperature sensor to the drive
converter.
The temperature sensor must be connected to the drive converter using a separate
cable (if at all possible, this cable should be shielded).
160
Kl. 14
PTC/
KTY
Kl. 15
Fig. 3-70 Connecting a temperature
sensor to MICROMASTER
MICROMASTER 440
6SE6400-5AW00-0BP0
Issue 10/03
5 V
574 Ω
A
D
Operating Instructions