Siemens SIMOTICS S-1FT7 Configuration Manual page 123

Synchronous motors
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Figure 5-9
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.
W =
Kinetic energy
ω =
Angular velocity
Coordinate the braking resistor ratings to the I
S-1FT7 synchronous motors
Configuration Manual, 09/2018, A5E45099423B AA
Circuit (schematic) with brake resistors
ω
• J
W
(
) / 2
2
J
/ kgm
• π
n
ω
( 2
/ 60 ) •
/ 1/s = angular velocity
n
/ rpm = speed
5.4 Brake resistances (armature short-circuit braking)
/ Ws = kinetic energy
= moment of inertia
2
t load capability.
2
Configuration
121

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