Limiting The Maximum Dc Link Voltage - Siemens SINAMICS G120 Operating Instructions Manual

Functions
8.7 Protection functions
8.7.4

Limiting the maximum DC link voltage

How does the motor generate overvoltage?
An induction motor operates as a generator if it is driven by the connected load. A generator
converts mechanical power into electrical power. The electric power flows back into the
inverter and causes V
Above a critical DC link voltage both the inverter as well as the motor will be damaged.
Before the voltage can reach critical levels, however, the inverter switches the motor off with
the fault message "DC link overvoltage".
Protecting the motor and inverter against overvoltage
The V
reaching critical levels.
The V
regenerative mode, e.g. in hoisting gear or when large flywheel masses are braked. Further
information on inverter braking methods can be found in Section Braking functions of the
inverter (Page 202).
There are two different groups of parameters for the V
the motor is being operated with U/f control or vector control.
Table 8- 26
Parameter for
U/f control
p1280 = 1
r1282
p1283
p1294
p0210
For more information about this function, see the List Manual (function diagrams 6320 and
6220).
194
in the inverter to increase.
DC
controller prevents – as far as the application permits – the DC link voltage from
DCmax
controller is not suitable for applications in which the motor is permanently in the
DCmax
V controller parameters
DCmax
Parameter for
vector control
p1240 = 1
r1242
p1243
p1254
p0210
DCmax
Description
V controller or V monitoring configuration(factory setting:
DC DC
1)1: Enable V controller
DCmax
V controller switch-on level
DCmax
Shows the value of the DC-link voltage above which the V
controller is active
V controller dynamic factor (factory setting: 100 %) scaling
DCmax
of the control parameters P1290, P1291 and P1292
V controller automatic recording ON-signal level(factory
-
DCmax
setting p1294: 0, factory setting p1254: 1)Activates or
deactivates automatic detection of the switch-on levels of the
V controller.
DCmax
0: Automatic detection disabled
1: Automatic detection enabled
Unit supply voltage
If p1254 or p1294 = 0, the inverter uses this parameter to
calculate the intervention thresholds of the V
Set this parameter to the actual value of the input voltage.
Operating Instructions, 01/2011, FW 4.4, A5E02999804A AB
controller, depending on whether
controller.
DCmax
SINAMICS G120C Inverter
DCmax