Functions
7.7 Protection functions
Inverter with CU240B-2 and CU240E-2 Control Units
178
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
7.7.3
Protecting the motor by calculating the motor temperature
The temperature calculation is only possible in the vector control mode (P1300 ≥ 20) and
functions by calculating a thermal motor model.
Table 7- 18 Parameter to sense the temperature without using a temperature sensor
Parameters Description
P0621 = 1
Motor temperature measurement after restarting
0: No temperature measurement (factory setting)
1: Temperature measurement after the motor is switched on for the first time
2: Temperature measurement each time that the motor is switched on
P0622
Magnetization time of the motor for temperature measurement after starting
(set
automatically as the result of motor data identification)
P0625 = 20
Ambient motor temperature
Enter the ambient motor temperature in°C at the instant that the motor data is
acquired (factory setting: 20°C).
The difference between the motor temperature and motor environment (P0625) must
lie within a tolerance range of approx. ± 5 °C.
7.7.4
Overcurrent protection
During vector control, the motor current remains within the torque limits set there.
During V/f control, the maximum current controller (I
max
controller) protects the motor and
inverter against overload by limiting the output current.
Method of operation of I
max
controller
If an overload situation occurs, the speed and stator voltage of the motor are reduced until
the current is within the permissible range. If the motor is in regenerative mode, i.e. it is
being driven by the connected machine, the I
max
controller increases the speed and stator
voltage of the motor to reduce the current.
Note
The inverter load is only reduced if the motor torque decreases at lower speeds (e.g. for
fans).
In the regenerative mode, the current only decreases if the torque decreases at a higher
speed.