Device functions
7.2 Startup modes
3RW44 soft starters
124 Manual, 03/2017, NEB535219502000/RS-AB/008
Breakaway pulse in combination with the voltage ramp or torque control startup
mode
This function is required for load machines with inverse torque behavior. Typical applications
are mills, crushers or drives with plain bearings. In such cases, it may be necessary to create
a breakaway pulse at the beginning of the machine's start process. The breakaway pulse is
set via the breakaway voltage and the breakaway time. Using the breakaway pulse, the high
limiting friction of the load can be overcome and the machine can be set into motion.
The breakaway pulse is used in conjunction with the start type of the voltage ramp, the
torque control, or the current limitation and overlays this during the set breakaway time.
The breakaway voltage is used to set the breakaway torque to be generated. The breakaway
torque can be up to 100% of the locked-rotor torque generated during direct-on-line starting.
The pulse must be high enough to ensure that the motor starts rotating as soon as the start
command is issued to the soft starter.
The breakaway time determines the period during which the breakaway voltage is to be
present. Once the breakaway time has expired, the soft starter ends its run-up procedure
with the selected startup mode, e.g. the voltage ramp or torque control. The selected
breakaway time should be at least long enough so that, after the set time has elapsed, the
motor does not remain stationary again but rather directly continues to accelerate in the
selected startup mode
If 0 ms is set as the breakaway time (default), the breakaway pulse function is deactivated.
Figure 7-4 Function principle of torque control breakaway pulse
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