Contact amplification for safety-related semiconductor outputs with testing (OSSD)
If control systems with integrated switching outputs reach their limits in the application, coupling relays and contact extension modules are used. Their task is contact amplification, contact multiplication and, due to the galvanic isolation between input and output, decoupling of the control and power levels.
The centrepiece of the extension module RK 6929 of the SAFEMASTER series, which is only 17.5 mm narrow, is the safety relay OA 5642 from Dold, which also opens up fields of application in the area of functional safety due to its forcibly guided contacts in accordance with IEC 61810-3, for example in mechanical and plant engineering as well as in applications for firing systems in accordance with EN 50156-1. For use within the scope of EN 61010-1, the clearances and creepage distances of the extension module RK 6929 between mains circuits and touchable voltages as well as between mains circuits are dimensioned according to double insulation.
If the current consumption of downstream actuators exceeds the power of the output of a safety controller or light grid, the extension module switches these actuators reliably and potential-free via its relay contacts. The input of the extension module RK 6929 corresponds to the interface type C class 1 in accordance with the ZVEI position paper CB24I and can therefore also be controlled by safety-related semiconductor outputs with testing (OSSD). Single and dual-channel versions of the extension module are available.
In conjunction with a suitable higher-level safety device, which diagnoses the switching status via the forcibly guided NC contacts, the extension module RK 6929 can therefore be used in applications up to Cat. 4 / PL e or SIL 3. Removable terminals, in screw and cage clamp technology, complete the advantages of the extension module by enabling convenient installation and simple device replacement.
