Technological Functions; Braking Functions Of The Frequency Inverter - Siemens SINAMICS G120 Operating Instructions Manual

Functions

5.10 Technological functions

5.10 Technological functions
The inverter offers the following technological functions:
● Braking functions
● Automatic restart and flying restart
● Basic process control functions
● Positioning down ramp
● Logical and arithmetic functions using function blocks that can be freely interconnected
Please refer to the following sections for detailed descriptions.
5.10.1

Braking functions of the frequency inverter

A differentiation is made between electrically braking and mechanically braking a motor:
● The motor is electrically braked by the inverter. An electrical braking is completely wear-
● Mechanical brakes are generally motor holding brakes that are closed when the motor is
Electrical braking and regenerative energy
If an induction motor electrically brakes the connected load and the kinetic energy that is
released exceeds the mechanical and electrical losses, then it operates as a generator. In
this case, the motor converts kinetic energy into electrical energy. Examples of typical
applications, in which regenerative operation briefly occurs, include:
● Grinding disk drives
● Fans
For certain drive applications, the motor can operate in the regenerative mode for longer
periods of time. Examples include:
● Centrifuges
● Cranes
● Conveyor belts with downward movement of load
Inverter braking methods
Depending on the particular application and the inverter type, there are different technologies
to handle regenerative energy.
● The regenerative energy is converted into heat in the motor (DC and compound braking)
● The inverter converts the regenerative energy to heat using a braking resistor (dynamic
● The inverter feeds the regenerative energy back into the line supply (regenerative
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free. Generally, a motor is switched off at standstill in order to save energy and so that
the motor temperature is not unnecessarily increased.
at a standstill. Mechanical operating brakes, that are closed while the motor is rotating
are subject to a high wear and are therefore often only used as an emergency brake.
braking)
braking)
CU240S and CU240E Control Units, FW 3.2
Operating Instructions, 03/2009, A5E02440075B AA