Configuration
5.4 Braking resistor (armature short-circuit braking)
1FK2 synchronous motors for SINAMICS S120
60 Configuration Manual, 06/2019, A5E46927724B AB
Dimensioning of the construction of braking resistors
Rating
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
2
Angular velocity
ω =
(2
• π
/ 60
) •
n
ω
/ 1/s = angular velocity
Coordinate the braking resistor ratings to the I
2
t load capability.
Calculating the braking time
The values for calculation are provided in Chapter "Data sheets and characteristics
(Page 72)".
B
=
J
Tot
• n
/ 9.55 •
M
Br
B
/ s = braking time
/ rpm = operating speed
Br
/ Nm = average braking torque
rtia
Tot
=
J
Mot
+
J
Ext
Tot
/ kgm
2
= moment of inertia
Mot
/ kgm
2
= motor moment of inertia
Ext
/ kgm
2
= external moment of inertia
Note
In determining the r
un-on distance, consider the friction of the mechanical transmission
elements (included in the calculation as an allowance in M
B
) and the switching delay times of
the contactors.
To avoid mechanical damage to the drive, mount mechanical stops at the end of
the
absolute traversing range of the machine axes.
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