Distributed frequency inverters with Safe Stop functionality

On the other hand, high availability of machines is vital. Economic efficiency requires quick restarts after safety-related shutdowns. SK 200E distributed frequency inverters from NORD DRIVESYSTEMS, though optimized for cost-efficient drive solutions, feature several safety functions which, depending on the switching device, enable safe shutdown procedures in high risk applications that comply with Category 4 or Performance Level e according to EN 13849-1.

Conventional frequency inverters in this performance class prevent motors from restarting by disconnecting the voltage supply or the 24 V control supply. By contrast, SK 21xE and SK 23xE models feature a certified safe pulse blocking device as well as digital inputs for the “Disable Voltage” and “Quick Stop” functions. These enable Stop Category 1 (controlled motor braking in line with SIL1), followed by Safe Torque Off (SIL3-compliant) or Stop Category 0 (SIL3-compliant) according to EN 60204-1.

Since the voltage supply is blocked without switching off the control or power electronics, the units remain on standby and are ready to be switched on without re-initialization after the safety circuit is closed. In addition to high availability, the inverters’ safety technology provides more economic benefits: contactor components are not required, and since the safety functions are activated electronically, there is no need for regular maintenance or exchange of electromechanical contacts.