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Publication SAFETY-AT017B-EN-P – July 2011
Introduction
In September 2006, NFPA 79 added an exception to the requirement for
disconnection of an actuator any time an E-stop is invoked. Safety PLCs
and other programmable devices such as drives are now allowed to be
the final switching element, provided they are designed to relevant safety
standards. This change is also in effect in IEC 60204-1. With this
modification, manufacturers will see a significant cost savings in terms
of equipment, wiring, and cabinet space.
DriveGuard safety solutions for Allen-Bradley PowerFlex AC drives
prevent a drive from delivering rotational energy to motors by integrating
an optional safety board in series with the power switching signals.
Along with a separate dedicated enable input on the base drive, this
option provides a certified solution that meets EN954-1, Category 3
(safe-off and protection against restart).
Features and Benefits
This application setup offers the following features and benefits:
•
This configuration increases the life of the drive because of the use
of soft stopping, such as removal of power to the gate firing circuits
of the drive’s output power devices.
•
This configuration requires a smaller panel size by using a control
contactor included within the PowerFlex DriveGuard drives to
replace external power contactors.
•
A drive with safe-off capabilities can offer increased productivity
through reduced downtime.
Important User Information
Solid state equipment has operational characteristics differing from those
of electromechanical equipment. Safety Guidelines for the Application,
Installation and Maintenance of Solid State Controls (publication
available from your local Rockwell Automation sales office or
http://literature.rockwellautomation.com
) describes some
important differences between solid state equipment and hard-wired
electromechanical devices. Because of this difference, and also because
of the wide variety of uses for solid state equipment, all persons
responsible for applying this equipment must satisfy themselves that
each intended application of this equipment is acceptable.
In no event will Rockwell Automation, Inc. be responsible or liable for
indirect or consequential damages resulting from the use or application
of this equipment.
The examples and diagrams in this manual are included solely for
illustrative purposes. Because of the many variables and requirements
associated with any particular installation, Rockwell Automation, Inc.
cannot assume responsibility or liability for actual use based on the
examples and diagrams.
No patent liability is assumed by Rockwell Automation, Inc. with respect
to use of information, circuits, equipment, or software described in this
manual.
