Allen-Bradley controllogix 1756-L55M12, User Manual

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111 Publication 1756-UM001G-EN-P - January 2007
Chapter
9
Configure Redundancy
Introduction This chapter explains how the ControlLogix redundancy system uses
an identical pair of ControlLogix chassis to keep your machine or
process running if a problem occurs with any equipment in a
redundant chassis.
Additional Resources
For additional information consult the ControlLogix Redundancy
System User Manua, publication 1756-UM523.
ControlLogix Redundancy
Overview
Redundancy provides for higher system availability by switching
control to a secondary controller chassis if anything in the primary
controller chassis fails. The redundant system switches from primary
to secondary due to:
•
power loss to primary chassis.
•
hardware or firmware failure of any module in the primary
chassis.
•
a major fault in the user program on the primary controller.
•
disconnection of a ControlNet tap or ControlNet cable to a
1756-CNB module in the primary chassis.
•
disconnection of an Ethernet patch cable from a 1756-ENBT or
1756-EWEB module in the primary chassis.
•
removal of any module in the primary chassis.
•
a user command that causes a switchover.
Topic Page
ControlLogix Redundancy Overview 111
Build a Redundant System 113
ControlNet Considerations in Redundant Systems 114
EtherNet/IP Considerations in Redundant Systems 115
Redundancy and Scan Time 116
Minimum System Requirements 116