Temperature Sensors - Siemens SINAMICS G120 Operating Instructions Manual

Functions
8.22 Thermal motor protection and overload responses
Procedure when measuring the temperature
After the power supply is switched-in and an ON command is issued, the motor is first
magnetized. If the "Determine the motor temperature after motor start" function has still not
been activated, the motor immediately starts to rotate after the ON command has been
issued. If this function is activated, the system waits until magnetization has been completed
and until the motor current is constant. The measuring intervals for this procedure are
specified using parameter P0622. The measurement itself is made if the current remains
constant over one measuring period within a certain tolerance bandwidth. Generally, several
measuring intervals are required. If the current is constant, then the actual current is
measured and the actual winding resistance is determined. This is then entered into
parameter R0623.
For a cold motor, this must approximately corresponds to the value of parameter P0350 of
the motor data identification; it must be appropriately higher for a motor in the warm
condition (at 130 ｰC approximately 150 %).
Note
In the following cases, the motor temperature is not measured:
• V/f operation
• Fault when measuring the current, e.g. the current isn't sufficiently constant
• For a flying restart the speed is too high
In these cases - when first accelerating after the power supply has been powered-up - an
average temperature value is used (approx. 47 °C). When the motor starts without powering-
down the power supply, the temperature does not change.
8.22.3

Temperature sensors

Data
Parameter range:
Warnings:
Faults:
Function chart number:
Description
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
8-154
P0601
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Operating Instructions, 11/2006, A5E00766042B AA
Control Units CU240S