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 manual
GWA 4NEB 535 2195-02 DS 01
Different stopping functions can be selected thanks of 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.
Notice
If guided stopping is selected as stopping mode (soft or 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
2 n
Torque-controlled
stopping mode
3
n
DC braking
Fig. 6-6: Stopping modes in general
Coasting down means that when the on command on 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 a natural run-down. A larger
centrifugal mass means a longer coasting-down.
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
s
6-11