Stopping Modes; Coasting Down - Siemens SIRIUS 3RW44 System Manual

6.3

Stopping Modes

6.3.1 Coasting Down

Typical applications for coasting down
SIRIUS 3RW44 System Manual
GWA 4NEB 535 2195-02 DS 04
Different stopping functions can be selected thanks to the large numbers of
applications for which the SIRIUS 3RW44 soft starter can be used. The motor
stop can be set optimally according to application and deployment.
If a start command is output while the motor is being stopped, this process is
aborted and the motor is started up again using the specified starting mode.
Note
If guided stopping is selected as stopping mode (soft stop, pump stop or
braking), it may be necessary to select a larger dimensioned branch (soft starter,
wiring, branch protection elements and motor), since the current exceeds the
motor rated current while the motor is being stopped.
Motor
speed
n
n
e
n
1
Coasting down
n
Torque-controlled
2
stopping mode
n
3
DC braking
Figure 6-6:Stopping modes in general
Coasting down means that when the on command to the soft starter is removed,
the energy feed to the motor via the soft starter is interrupted. The motor will
coast down freely, only driven by the mass reactance (centrifugal mass) of the
rotor and the load. This is designated as a natural run-down. A larger centrifugal
mass means a longer coasting-down.
Coasting down is used for loads with no special requirements in terms of
stopping behavior, e.g. large fans.
3
1 2
Stop command
at soft starter
Device Functions
Time (t)
s
6-11