Siemens SIRIUS 3RW44 - Page 96

Device Functions
SIRIUS 3RW44 System Manual
6-4 GWA 4NEB 535 2195-02 DS 04
Figure 6-1:Function principle of voltage ramp
Figure 6-2:Function principle of voltage ramp/ torque curve
Typical applications for voltage ramps
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 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.
5_01_Funktionsprinzip Spannungsrampe .wmf
Voltage in %
Time (t)
s
U
Motor
100 %
100 %
Voltage at
the motor
Parameterizable
start voltage
Parameterizable
starting time
Longer starting time
1
Short starting time
2
1
2
5_02_Funktionsprinzip Spannungsrampe_Drehmomentverlauf.wmf
Motor
torque (M)
Nm
Speed (n)
min-1
M
Direct on-line starting
(maximum torque
that can be generated)
M
Nom
Motor has run up and is
in nominal operation (n
Nom
).
The runup is detected and the
bypass contacts close.
3
Parameterizable
start voltage
M
Soft start
Longer ramp time
M
Load (e.
g
. Fan)
1
Parameterizable
torque starting time
1
Acceleration
torque
2
Short ramp time
M
Soft start
2
3