Limiting The Maximum Dc Link Voltage; Advanced Commissioning - Siemens SINAMICS G110M Operating Instructions Manual

6.6.5

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 energy into electrical energy. The electrical energy flows back into the
inverter. If the inverter cannot dissipate the electrical energy, for example in a braking
resistor, then the DC-link voltage Vdc increases in the inverter.
Above a critical DC-link voltage both the inverter and 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 Vdc_max control avoids an excessively high DC-link voltage, assuming that the
application permits this. The Vdc_max control increases the ramp-down time of the motor
when braking, so that the motor feeds back only as little energy to the inverter as is covered
by the losses in the inverter.
The Vdc_max control is not suitable for applications where the motor is continuously in the
generator mode. This includes, for example, cranes or applications involving braking large
moments of inertia.
Parameter for Vdc_max control
The parameters differ depending on the motor control mode.
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).
Distributed converter for SIMOGEAR geared motors
Operating Instructions, 06/2016, FW V4.7.6, A5E31298649B AG
Braking functions of the inverter (Page 210)
Parameter for
vector control
p1240 = 1
r1242
p1243
p1254
p0210
Manuals for your converter (Page 335)
Description
VDC controller configuration(factory setting: 1)
1: VDC controller is enabled
Vdc_max control switch-on level
DC-link voltage value above which the Vdc_max control is acti-
vated
Vdc_max control dynamic factor (factory setting: 100 %) Scaling
closed-loop control parameters p1290, p1291 and p1292
Vdc_max control automatic ON level sensing(factory setting
depends on the Power Module)
0: Automatic detection disabled
1: Automatic detection enabled
Unit supply voltage
If p1254 or p1294 = 0, the inverter uses this parameter to calcu-
late the switch-in thresholds of the Vdc_max control.
Set this parameter to the actual value of the input voltage.

Advanced commissioning

6.6 Protection functions
205