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Drives offer built-in safety

01 February, 2006

Drives offer built-in safety

Rockwell Automation is offering drives-users a simpler and more convenient alternative to the wiring, complexity and cost of traditional two-contactor safety systems. A new option on the company`s PowerFlex 700S AC drives disables the drive in the event of a potential hazard, stopping the controlled machine from moving until it is safe to do so.

The system, called DriveGuard, is aimed at medium-to-high risk applications, and complies with EN954-1 Category 3. Using a hardwired "enable" signal and a positive-guided relay, it removes power from the drive`s IGBT output power transistors. The relay also provides feedback to the safety system on the status of the drive. The controlled motor cannot be restarted until the safe-off condition is satisfied.

Although Rockwell has previously offered DriveGuard as an option on its general-purpose PowerFlex 60 drive, the facility is now available on the more powerful PowerFlex 700S model, which spans ratings from 0.75-800kW, at 400-690V.

The development is part of a Rockwell effort to make it easier for users to build functional safety features into their machines by "zoning" - creating a safe area that allows part of a production line to slow down or stop while the rest of the line remains active. The hazard can be removed or corrected without stopping the entire line, eliminating lengthy shutdowns. Once the hazard has been cleared, the line resumes normal operation rapidly.

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