FWS AND AWR
FAIL-SAFE STANDSTILL MONITORS

Series AZR 31 S1 and FWS fail-safe standstill monitors are used to capture machinery standstill and to control connected solenoid interlocks. With series AZR 31 S1, it is possible to build protective devices that achieve category 4, PL e in accordance with ISO 13849-1, depending on the external wiring in connection with a safety relay module.

STRUCTURE AND MODE OF OPERATION OF THE SAFE STANDSTILL MONITORS

The standstill monitors have an internally redundant design and are equipped with two safety relays with monitored forcibly guided contacts. The series-connected interfaces of the relays act as output contacts. The solenoid interlocks can only be activated and the safety guards opened when the respective machine has come to a standstill. This is done via the output contacts of the standstill monitors.

AZR 31 S1 AND FWS SIDE BY SIDE

The AZR 31 S1 standstill monitor is sensorless and is connected directly to a three-phase AC motor. In this way, it measures the frequency of the induced voltage. The enable fields close when the motor is at a standstill. LEDs are used to display the various operating states. The standstill monitors of the FWS series evaluate pulses generated by rotary movements. These can come from incremental encoders or inductive proximity switches, for example. The enable paths close as soon as the detected pulse sequence falls below the limit frequency. Fail-safe standstill monitors are equipped with integrated system diagnosis for rapid and simple fault detection. Users receive information about the switching status of the standstill monitor and the connected pulse generators via the multifunction LED. The Schmersal Group provides detailed product descriptions of the safe standstill monitors in its comprehensive online catalogue under the category ‘Safe signal processing’.