Bonfiglioli innovation for Functional Safety with a digital approach

Reducing risks for operators and machines while simplifying the safety concept.

One of the latest innovations developed in Bonfiglioli Electronics R&D Department is about the extension of the range of safety functions available on frequency converters and servo drives, to open new opportunities at the application level and to avoid the need of external components, which generate additional costs and complexity in the electrical installation.

The project has focused on both open loop and closed loop safety functions, with the possibility to control them not only via safe digital I/Os, but also via safety fieldbuses (FSoE, Profisafe), extending in this way the level of flexibility and digital integration of the system.

One main activity has been the development of SLS (safely limited speed) safety function, both sensorless and in closed loop, with the possibility to dynamically set several different safe speed thresholds directly via safety fieldbus.

Such a a function is particularly appreciated in material working machinery, where it is often required to set different safe speed limits according to the tool in use and avoiding unnecessary downtimes.

The possibility to flexibly do this with integrated safety, and avoiding the use of encoders thanks to sensorless safety technologies, ensures the protection of the user and of the machine itself in a robust, cost effective and easily certifiable way.

The innovation has been accomplished through the development of a single control unit, which is able to execute both the SLS function, according to the standard EN61800-5-2, and the process-dependent speed limitation. The superimposition of both functions needs the independent parameterization of two limits. A first parameter defines the limit of the safety function SLS and a second parameter determines the threshold value for the SLS function with sliding process-dependent speed limitation. This second value is not fixed and can vary during the manufacturing process. In order to avoid unnecessary interruptions of the manufacturing process, a real-time adjustment of the sliding speed limit is required. This requirement has been implemented by a parameter transmission via safety fieldbus (FSoE, ProfiSafe), giving maximum flexibility at the system level.

The execution of both functions, SLS according the standard EN61800-5-2 and SLS function with sliding limits, is possible with safety encoders and also sensorless.

Bonfiglioli’s innovation is aimed, more in general, at offering frequency converters with advanced integrated safety functions for a reduction of wiring, maintenance and servicing effort together with a simplification of the safety concept.

These safety functions will be available on the next generation of Bonfiglioli frequency converters, planned to be launched in 2020.