Thermal motor model
Function description 75
Version: 1.5
17 Thermal motor model
Note
Reference values for the thermal motor model:
S-0-0012; S-0-0111, S-0-0135; S-0-0196, P-0-0052; P-0-0061; P-0-0062, P-0-0066 and
P-0-0063.
The thermal motor model calculates the current thermal utilization (P-0-0063 in %) of the motor. This
utilization display serves to determine the application-specific utilization reserves. Furthermore, the thermal
motor model offers motor protection by means of the dynamic detection of overloads. The motor data for
Beckhoff servo motors from the series AM8000 originate from the electronic name plate (offline from the
motor data files *.xeds). The motor data generator can be used to create motor data files for third-party
motors.
If a temperature sensor (e.g. KTY83-110, KTY84-130, PT1000) is installed in the motor that allows a
temperature evaluation over the entire operating temperature range (see motor technical data), the motor is
initialized in accordance with the current temperature.
The operating temperature cannot be measured if PTC thermistors are used that exhibit a fast increase in
the resistance value in the region of the nominal response temperature (motor cut-off temperature). In this
case the motor is initialized in accordance with the max. permissible ambient temperature (40 °C). It should
be noted here that after switching off the 24 V system supply a waiting time (5 times the motor time constant
P-0-0062, time constant 1) is required before switching on again. This ensures the thermal motor protection
with the motor model. The value of the load display is incorrect if the waiting time is not adhered to.
17.1 Functionality from firmware v2.10
A more precise thermal motor model is used from firmware v2.10. This second order model calculates the
winding temperature with the help of the winding time constant (P-0-0062, time constant 2). Furthermore, a
speed-dependent calculation of the iron losses is carried out. This ensures a considerably improved
utilization of the motors.
Note
Calculation of the copper and iron losses!
For the calculation of the copper and iron losses must be the IDNs S-0-0111, S-0-0196 and
P-0-0066 filled with reliable and engine-specific data!
17.2 Functionality up to firmware v2.06
Up to and including firmware v2.06, the copper losses are used in connection with the thermal time
constants of the stator and the housing (P-0-0062, time constant 1) for a utilization display.
Motor windings with a small thermal mass are protected by means of a time limitation of the peak current
(P-0-0052, default: 3 s).
The model is initialized independently of the temperature sensor on the basis of the max. permissible
ambient temperature (40 °C).
Note
Calculation of the copper losses!
For the calculation of the copper losses must be the IDNs S-0-0111 and P-0-0066 filled
with reliable and engine-specific data!
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