Siemens SINAMICS G120 Instructions d'exploitation télécharger pdf (Page 180)

Functions

7.7 Protection functions

Inverter with CU240B-2 and CU240E-2 Control Units

178 Operating Instructions, 01/2011, FW 4.4, A5E02299792B AB

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- 29 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 U/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.

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Siemens SINAMICS G120 Instructions d'exploitation Page 180