Functions
7.9 Technological functions
Inverter with CU240B-2 and CU240E-2 Control Units
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
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7.9
Technological functions
The inverter offers a series of technology functions, e.g.:
● Braking functions
● Automatic restart and flying restart
● Basic process control functions
● Logical and arithmetic functions using function blocks that can be freely interconnected
Please refer to the following sections for detailed descriptions.
7.9.1
Braking functions of the 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-
free. Generally, a motor is switched off at standstill in order to save energy and so that
the motor temperature is not unnecessarily increased.
● Mechanical brakes are generally motor holding brakes that are closed when the motor is
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.
7.9.1.1
Comparison of electrical braking methods
Regenerative power
If an induction motor electrically brakes the connected load and the mechanical power
exceeds the electrical losses, then it operates as a generator. The motor converts
mechanical power into electrical power. Examples of 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, e.g.:
● Centrifuges
● Hoisting gear and cranes
● Conveyor belts with downward movement of load (vertical or inclined conveyors)