Safe controls for safety brakes minimise risks

The “ROBA-SBCplus” brake control, developed together with Pilz, is technically superior in every respect in terms of safety contactor circuits. It offers, among other things, wear-free, electronic switching, it foregoes programming, saves wiring and reduces the construction space requirements. The module prototype-inspected by the TÜV (Technical Inspectorate) can be deployed up to the highest Performance Level PLe and SIL 3.

In order to enable safety brakes to contribute towards risk reduction in machines and systems, they require a reliable control. Vertical axes or stage equipment, for example, rank among the particularly hazardous machine parts. In order to protect people from all hazards in such situations, the remaining functional risks in accordance with safety standard DIN EN ISO 13849-1 must first be assessed, and subsequently suitable measures for the reduction of risks must be taken. As a mechanical component, the brake falls under the category of functional safety in accordance with this standard.

The safety brakes from Mayr power transmission function according to the “fail-safe” principle and are closed in a de-energised state. The brake control has the task of reliably interrupting the current in the magnetic coil when switching the brake off. The brake control module works using wear-free electronic semi-conductors, and therefore achieves practically unlimited switching frequency and switching reliability.

The fail-safe internal construction of the control includes, among other things, the internal diagnostic checks for short circuit, earth short-circuit and line interruptions, as well as reliable overexcitation for releasing the brake and switching to a reduced holding voltage with an open brake. Numerous other safety functions permit a comprehensive error diagnosis: as a result, the output voltage and the switching times for the brake are monitored. The signal evaluation of the release monitoring with plausibility check enables switching condition monitoring of the brake.

Thanks to electronic, wear-free semi-conductor contacts, the ROBA-SBCplus is substantially more reliable and safer than the contactor circuits; and it foregoes complex hardware. The module replaces numerous functional components. Their reduction saves a significant amount of space in the control cabinet due to the reduced wiring and constructional space requirements.

The greatest savings potential is achieved if the performance capability of the module is fully utilised and two brakes are simultaneously reliably controlled. Brakes with a 5 A nominal current can be connected, and the two brakes do not have to be identical in construction. Easy parameterability and the elimination of programming and validation round up the features of superiority.

Contact:
Chr. Mayr GmbH + Co. KG, Eichenstraße 1, 87665 Mauerstetten, Dipl.-Ing. (FH) Hermann Bestle
Tel.: 08341/804-232, Fax: 08341/804-49232
E-Mail: hermann.bestle@mayr.de, Web: http://www.mayr.com