Ss1, Two Switching Devices Connected In Series; Description - Siemens SINAMICS DCM User Manual

SS1, two switching devices connected in series

6.1

Description

When selecting the safety function (actuating the mushroom pushbutton), the instantaneous
NO contacts are immediately opened in the 3SK1122-2CB4x
consequence, at the SINAMICS DCM, the OFF3 function (fast stop) is initiated via the
programmable digital input DIO4 (X177.15). The drive is braked along a ramp that can be
adjusted using p50269. The down ramp is not monitored.
As soon as the SINAMICS DCM identifies that the motor is at a standstill (speed of 0), the
firing pulses are inhibited and the power disconnected.
Independent of the down ramp that has been adjusted, after the time set at the safety relay,
the delayed contact of the safety relay is opened. These contacts initiate the E-Stop function
at the SINAMICS DCM.
The SINAMICS DCM reduces the armature current, inhibits the firing pulses and opens the
armature contactor. The "E-Stop active" signal must be integrated in the feedback circuit of
the safety relay via an interface relay at digital output DO3 (X177.22).
At the same time that the E-Stop function is selected, the NO contacts of the safety-related
output expansion 3SK1211-2BB40 open via the internal communication of the 3SK safety
relays; as a consequence, the safety-related coupling relays to control the armature and field
circuits are opened.
The motor current therefore goes to zero and in turn, the motor torque also goes to zero.
The motor coasts down if a speed of zero has still not been reached.
The drive system can only be considered to be in a torque-free state after the delay time has
expired and the power switching devices opened.
In the circuit examples, the energy feed to the field power units as well as to the armature
circuit is interrupted. Two power switching devices connected in series are used in the
armature circuit. Controlling the field contactor is optional. However, in this case, the motor
cannot be considered to be in a no-voltage condition.
Note
For setting p50269=0 (OFF3 ramp down time), the drive brakes at the current limit. The
actual ramp-down time is influenced by the driving forces of the mechanical system. The
safety relay delay should be set longer than the actual ramp-down time.
(x) order code for the time delay:
1
1 = 0.05 ... 3 s
2 = 0.5 ... 30 s
4 = 5 ... 300 s
Application document for functional safety STO, SS1 (ISO 13849-1)
Compact User Manual, 09/2016, A5E34871844AM
safety relay. As a
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