When operating systems, after activating a safety circuit, it must be ensured by opening a protective hood or door that no rotating system components lead to work accidents. Despite their design for cost-optimized drive solutions, the decentralized Frequency inverters of the SK 200E series from Nord Drivesystems on various safety functions with which safe shutdown paths with high risk classification according to category 4 or performance level e according to EN 13849-1 can be realized.
While conventional inverters of this performance class prevented restarting of the motor by completely disabling the 24-V control voltage or supply voltage, the SK 21xE and SK 23xE types are equipped with a certified safe pulse inhibit and have digital inputs for the voltage lock functions "And" quick stop ". In this way, the frequency inverter can be used to implement stop category 1 (targeted braking of the drive according to SIL1) with subsequent torque switch-off (according to SIL3) or stop category 0 (according to SIL3) in accordance with EN 60204-1.
Since activation of the pulse locks does not switch off the control and power electronics, the devices remain online and are immediately available again immediately after closing the safety circuit without reinitialization. In addition to the high availability, the safety technology of the inverter offers additional economic advantages: The use of contactor components is unnecessary, the electronic circuit of the locking functions saves the regular maintenance and replacement of wearing electromechanical contacts.