Basic Mechanisms Of Si Functions; Safe Standstill - Disconnecting The Energy Feed - Siemens SINUMERIK 840D Description Of Functions

11.03

3.1 Basic mechanisms of SI functions

The safety functions are available in all modes and can communicate with the
process using safety-related input/output signals. They fulfill the requirements
of safety category 3 (to EN 954-1) and SIL 2 (acc. to IEC 61508).
3.1.1 Safe standstill – disconnecting the energy feed
Fig. 3-1
Fig. 3-1 illustrates 4 basic possibilities of switching a motor into a no-torque
condition. The mode of operation of these methods differ.
¨ Main breaker:
Each machine must be equipped with at least one breaker. This allows the
machine to be completely electrically isolated from the line supply. This is
usually implemented using the main breaker. This measure provides protection
against electric shock when working with live components. When powered-
down, the breaker must be locked-out to prevent accidental re-closure.
≠ Integrated line contactor:
The entire converter can be electrically isolated using the line contactor. As far
as the converter is concerned, this measure also corresponds to a STOP A. In
the past, for an EMERGENCY STOP, the converter/motor was brought into a
no-torque condition using the integrated line contactor corresponding to a
STOP B/C. However, electrical isolation is not absolutely necessary for an
EMERGENCY STOP.
Æ Pulse cancellation in the gating unit
The fastest way of switching a drive, axis-by-axis, into a no-torque condition is
by canceling the pulses in the gating unit. However, this measure is still not a
safety-related measure. This means that it is still not possible to electrically
isolate the drive converter DC link (600V) from the motor.
© Siemens AG 2003 All Rights Reserved
SINUMERIK 840D/SIMODRIVE 611 digital SINUMERIK Safety Integrated (FBSI) - Edition 11.03
Input to network Drive 1
4
2
3
1
Safe standstill – disconnecting the energy feed
3 Safety-Related Functions
3.1 Basic mechanisms of SI functions
Drive 2
Centrally
1. Main switch
2. Line contactor
Axis-specifically
3. Control pulses
4. Control voltage
M M
Effect -> central
Effect -> central
Effect -> axis-specific
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