Siemens SINUMERIK 840D sl Manual page 228

Typical circuit diagrams
7.7 Circuit Manual Group =5
A corresponding feedback from the Control Unit (=4.-K11-X122:8, DI/DO 9) and the interface
relay (=5.-K28) is linked with the safety relay (=5.-K21) in the On circuit. The On circuit is
enabled only when the feedback from the safe standstill functions properly.
The "Safe Standstill" function is monitored actively after each stop action.
Holding brake
A braking current > 2 A DC means that the power cannot come directly from the Motor
Module, but will be supplied from a separate infeed.
The holding brake is controlled time-coordinated by the PLC logic using PLCA527. When the
drive is stopped, an off-delayed contact is used for the contactor (=5.-K24) to also safely
shutdown the brake using hardware. This means a fault in the PLC cannot cause an
incorrect control of the brake when the drive is stationary.
7-40
Guide for the SINUMERIK 840D sl machine configuring
Manual, 07/2006 Edition, 6FC5397-6CP10-0BA0