Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 104)

100%
Motor
Speed
7 or 15%
Slow
Speed Start Run Stop
Braking
Coast-to-rest
Time (seconds)
Fig. 3.9-11
Soft starters with positioning speed in one direction and controlled braking
100%
Motor
Speed
7% or 15%
Slow
Speed Start Run
Time (seconds)
Brake
Slow Speed
Braking
Slow Speed Braking
Coast-to-rest
Fig. 3.9-12
The Accu-Stop™ function enables precise (accurate) positioning in one direction and precise stopping. In
the braking phase, the motor is in a first phase broken until the positioning speed is reached. Complete
braking happens as soon as a stop command is issued.
3.9.9 Linear acceleration and deceleration by speed feedback
Feedback of the motor speed can be used for linear acceleration and stoppage of a drive. The
motor voltage is adjusted – largely independently of the torque requirement of the drive – in
accordance with the speed feedback so that starting and braking follow the selected character-
istic. The resulting motor current is a function of the required voltage.
100%
Percent
Speed
Start Run Stop
Time (seconds)
Fig. 3.9-13
Linear acceleration and deceleration of a drive by speed feedback via tachometer.
3.9.10 Direct start with full voltage
Just as with solid state (semiconductor) contactors, a start with full voltage and hence with full
motor torque can be performed with soft starters.
LVSAM-WP001A-EN-P - April 2009 3-28