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Functions
8.2 Run-down
Parameters
Stopping time
DC braking torque
Dynamic braking torque
DC braking delay
8.2.6.3
Reversing DC braking with a reversing contactor assembly
Operating principle
In the stopping mode "Reversing DC braking", the motor is strongly braked with an external
reversing contactor assembly. To avoid the motor turning in the opposite direction after braking,
braking is divided into 2 braking phases. In the first braking phase, the 3RW55 soft starter brakes
with reversing operation (external reversing contactor assembly), up to approx. 80% (factory
setting) of the energy has been reduced. This energy is determined by the 3RW55 soft starter
and corresponds to the starting energy. In the second braking phase, the 3RW55 soft starter
brakes by DC braking (without the DC braking contactor) and reduces the remaining 20% of the
energy. DC braking is brought to an end by standstill detection. Standstill detection requires use
of the function "External motor standstill detection (Page 162)" or "Sensorless motor standstill
detection (Page 162)".
160
Description
The stopping time specifies the period during which the DC braking torque is to be generated
on the motor. The chosen braking time should be long enough to bring the load to a standstill.
To achieve an adequate braking effect down to standstill, the centrifugal mass of the load
should not exceed that of the motor. The length of the stopping time should be chosen such
that the motor comes to a standstill.
The actual stopping time may vary with this braking process.
•
Factory setting: 10 s
•
Setting range: 0 ... 360 s
•
In steps of: 0.1 s
With the DC braking torque, the braking force of the motor in the second phase of braking can
be set. The dynamic braking torque must be increased if the motor is to accelerate again during
DC braking.
•
Factory setting: 50%
•
Setting range: 20 ... 100%
•
In steps of: 5%
The dynamic braking torque determines the braking effect in the first phase of braking to
reduce the speed of the motor. After that, braking by DC braking is continued automatically.
•
Factory setting: 50%
•
Setting range: 20 ... 100%
•
In steps of: 5%
The DC brake delay starts when the motor OFF command ("Motor CW" and "Motor CCW" = 0)
is detected. The motor coasts freely while the DC brake deceleration time elapses. The dynamic
DC braking is not started until the DC braking delay has elapsed.
The motor brakes by free coasting, which means less energy is required for subsequent dy‐
namic DC braking. This reduces the risk that the 3RW55 soft starter may overheat during
dynamic DC braking.
This parameter is used for "Stopping mode" and ignored for "Alternative stopping mode".
•
Factory setting: 0 s
•
Setting range: 0 ... 360 s
•
In steps of: 0.1 s
SIRIUS 3RW55 and 3RW55 Failsafe Soft Starters
Equipment Manual, 02/2022, A5E35630887002A/RS-AF/006
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