Posted to News on 9th Apr 2008, 22:10
Non-contact safety switches need no separate relay
Schneider Electric is introducing its new Telemecanique Preventa XCSDM3 and XCSDM4 Hall Effect non-contact safety switches, which have been designed to eliminate the need for an external safety relay to monitor safety circuit input and output integrity.
Compact, easy to install and highly tolerant of misalignment, magnetic safety switches are used as safety interlocks on movable machine guards and/or where frequent wash down takes place. Standard safety switches are wired back to a panel with a safety relay for failsafe operation.
The new XCSDM3 and XCSDM4 models incorporate a safety relay, enabling the devices to self-check and detect their own failure without the use of an additional external safety relays. They can directly drive two external 24V DC contactor coils (via two internally OSSD safety PNP outputs) and, in the case of the XCSDM4, monitor those external contactors' normally-closed auxiliaries (known as EDM) to directly and safely control electric motor-driven loads.
Save money and panel space
Certified for use in SIL2/Cat3 and SIL3/Cat4 safety circuits (as per EN 61508/62061 and EN ISO 13849-1) the devices offer a wide range of benefits for OEMs and end users, the main advantages being the convenience of buying a single device - which reduces cabling complexity and panel space - and a lower price compared with buying an individual switch and safety relay.
Features include robust construction and IP69K resistance to jet washing, as well as IP67 for washdown; simple diagnostics via a tri-colour LED on the switch body plus a PNP output for remote I/O or PLC connection; a wide operating temperature range (-25 to +75degC), and the ability to connect up to 32 devices in series.
The devices permit up to nine approach directions and are magnetically coded to prevent tampering. Pre-wired versions (2m, 5m and 10m) are available, as well as M12 connector versions for ease of maintenance.
David Collier, Schneider Product Manager for Safety, comments: "This does not spell the end for the safety relay, but it does offer machine builders and end users the opportunity to simplify their safety wiring especially on machines with distributed safety loops. At the same time they reduce costs and panel space."
The XCSDM3 and XCSDM4 are the latest editions to Schneider Electric's Preventa range of XCS safety switches, which includes metal and plastic mechanical safety interlocks, solenoid safety interlocks and safety limit switches.
