Motor And Converter Protection By Limiting The Voltage - Siemens SINAMICS G110M Operating Instructions Manual

Advanced commissioning

8.26 Motor and converter protection by limiting the voltage

8.26 Motor and converter protection by limiting the voltage
Overview
An electric motor converts electrical energy into mechanical energy to drive the load. If the
motor is driven by its load, e.g. by the inertia of the load during braking, the energy flow
reverses: The motor operates temporarily as a generator, and converts mechanical energy into
electrical energy. The electrical energy flows from the motor to the converter. If the converter
cannot output the electrical energy supplied by the motor, e.g. to a braking resistor, then the
converter stores the energy in its DC link capacitance. As a consequence, the DC link voltage Vdc
in the converter is higher.
An excessively high DC link voltage damages both the converter and the motor. The converter
therefore monitors its DC link voltage and switches off the connected motor and outputs fault
"DC link overvoltage".
Function description
Protecting the motor and converter against overvoltage
Figure 8-73
The Vdc_max control lengthens the motor ramp-down time when braking. Consequently, the
motor feeds only so much energy back into the converter to cover the losses in the converter. The
DC link voltage remains within the permissible range.
The Vdc_max control is not suitable for applications where the motor is in continuous
regenerative operation, e.g. as is the case for cranes and centrifuges.
328
Simplified representation of the Vdc_max control
Electrical braking (Page 311)
Distributed converter for SIMOGEAR geared motors
Operating Instructions, 10/2020, FW V4.7 SP13, A5E31298649B AL