Siemens SIMOTICS 1FT2104-4AF - Dimensioning of the Construction of Braking Resistors

Configuration
5.4 Braking resistor (armature short-circuit braking)
1FT2 synchronous motors for SINAMICS S120
Configuration Manual, 03/2021, A5E50645584B AA
67
Figure 5-6 Circuit (schematic) with braking resistors
5.4.2 Dimensioning of the construction of braking resistors
Rating
NOTICE
Destruction of the braking resistors
Braking from the rated speed is not permitted any more frequently than every 2 minutes;
otherwise the resistors will be destroyed.
• Maintain a time interval of at least 2 minutes or longer between braking operations.
•
When required, specify other braking cycles when ordering.
You can dimension the braking resistor so that a surface temperature of 300 °C can occur
briefly (max. 500 ms).
The external moment of inertia and the intrinsic motor moment of inertia are decisive when
dimensioning the braking resistors.
When ordering the braking resistors, determine the kinetic energy involved.
Kinetic energy
W = (ω
2
• J ) / 2
W / Ws = kinetic energy
J / kgm
2
= moment of inertia
Angular velocity
ω = (2 • π / 60
) • n
ω / 1/s = angular velocity
n / r/min = speed
Coordinate the braking resistor ratings to the I
2
t load capability.