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Bargteheide, Germany, 2007-12-12 Many machines and plants, e.g. machine tools such as milling machines, need to fulfill strict operator safety standards: when a safety circuit is activated, operators must be safe from rotating machine parts.

Many machines and plants, e.g. machine tools such as milling machines, need to fulfill strict operator safety standards: when a safety circuit is activated, operators must be safe from rotating machine parts. At the same time, high availability is essential since machine downtime costs both time and money. The compact NORDAC SK 530E frequency inverter from NORD Drivesystems, which features the safety function "Safe Stop" according to EN 954-1 category 3 (stop categories 0 and 1), is designed for such tasks. The unit ensures standard-compliant restart protection for asynchronous motors, replacing the contactor between motor and inverter with an integrated inverter function (safe torque off) which is based on a separate supply voltage for the electronic power modules (IGBT). This external 24 V voltage is supplied by a safety disconnecting device – depending on the build type, it can optionally enable compliance with safety category 4. Compared with the currently used contactor technology, the SK 530E minimizes material costs and maintenance efforts and increases availability. Since the "Safe Stop" function does not require a power shutdown, the inverter does not need to be initialized during restart. Moreover, the life span of the units is increased thanks to their purely electronic switching mechanisms.