Introduction
1.2 Preliminary remarks
Application document for functional safety STO, SS1 (ISO 13849-1)
12 Compact User Manual, 09/2016, A5E34871844AM
Safe Torque Off is a safety function to avoid unexpected starting in accordance with
EN 60204-1. STO prevents the supply of energy to the motor, which can generate a torque
and corresponds to Stop Category 0. The motor is stopped in an uncontrolled fashion.
When a large DC smoothing reactor is used in the armature circuit the current decay time
of 0.05s before switching the firing pulses off may possibly not be sufficient for STO / stop
category
0. If the armature current at this instant is not pulsating, inverter shoot-through
can occur. As a consequence, in this particular case we recommend that the output e
pansion of the safety relay is shut down with a short delay of 0.5 s. Setting the output e
pansion, see circuit example SS1.
option that does not contain any free-wheeling diode for the field cur-
rent is used, the use of SS1 / stop category
1 is recommended to protect the field contac-
tor. This is necessary because the braking voltage of the opening contacts of a field
contactor (
line side) does not suffice to activate the free-wheeling function of the 2Q thyri
Safe Stop 1 (SS1, time-controlled)
Safe Stop 1 is based on the "Safe Torque Off" function. This means that a Category 1 stop
according to EN 60204-1 can be implemented. The drive is actively braked to a standstill.
The energy feed is safely shut down after a time, which can be adjusted at the safety relay,
after the motor should safely remain stationary (STO).
To Next Page
Loading...
Need help?
General
