Siemens SIRIUS 3RW44 User Manual page 96

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
Figure 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
2 M
Soft start
Longer ramp time
3 M
Load (e. g. Fan)
Figure 6-2: Function principle of voltage ramp / torque curve
The voltage ramp function principle is suitable for all types of application.
If test runs with the application are carried out using motors that are smaller than
those to be used in the actual system, we recommend using 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 Chapter 6.2.3
"Breakaway Pulse in Combination with the Voltage Ramp or Torque Control
Starting Mode". 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 06