Siemens Sirius 3RW44 System Manual page 76

Device functions
Typical applications for voltage ramps
6-4
Voltage in %
U 100 %
Motor
1
2
Parameterizable
start voltage
1 Short starting time
Longer starting time
2
Fig. 6-1: Function principle of voltage ramp
Motor
torque (M)
Nm
M
Direct on-line starting
(maximum torque
that can be generated)
M
Nom
Parameterizable
start voltage
M
1
Soft start
Short ramp time
M
2
Soft start
Longer ramp time
3 M
Load (e. g. Fan)
Fig. 6-2: Function principle of voltage ramp/ torque curve
The voltage ramp function principle is suitable for any type of application.
If test runs are carried out using motors that are smaller than those used in
actual applications, we recommend you use the voltage ramp starting mode.
For machines requiring a breakaway pulse (inverse load response, e.g. in mills or
crushers), the breakaway pulse must be set as described in Section 6.2.3. The
voltage ramp+current limiting (U+current limiting) starting mode is
recommended for heavy starting.
Parameterizable
starting time
1
Acceleration
2
torque
3
Parameterizable
torque starting time
Time (t)
s
100 %
Voltage at
the motor
Speed (n)
min-1
Motor has run up and is
in nominal operation (n ).
Nom
The runup is detected and the
bypass contacts close.
SIRIUS 3RW44 manual
GWA 4NEB 535 2195-02 DS 01