Mitsubishi Electric MELSEC iQ-R Series User Manual page 388

Error in the redundant function module
• When an error has been detected on a redundant function module, a continuation error occurs on the CPU module, and the
control system and standby system continue operating without being switched. Check the error code, and perform online
module change if the redundant function module has failed. ( MELSEC iQ-R Online Module Change Manual)
• When the redundant function module was removed from the base unit or a failure has occurred in the base unit and a
communication error has been detected in the communication between the redundant function module and a CPU module,
a stop error occurs on the CPU module and the systems are switched. In this case, check the error code and eliminate the
error cause.
If the CC-Link IE Field Network module has not been mounted or no redundant extension base unit is
connected, the systems may not be switched when a communication error has been detected in the
communications between the redundant function module and the CPU module.
To switch the systems when the redundant function module has been removed from the base unit or a failure
has occurred in the main base unit, mount the CC-Link IE Field Network module or connect a redundant
extension base unit.
When both systems operate as standby systems
• If a communication error is generated due to a tracking cable error during system switching, both systems may operate as
standby systems. When an error occurs with the tracking cable, each L ERR LED of the redundant function modules turns
on. In this case, replace the tracking cable with a new one as soon as possible. If both systems operate standby systems,
connect a new tracking cable properly and turn off and on or reset the CPU module of one system so that the other system
will operate as the control system.
• If a WDT error or a hardware failure of the CPU module has occurred in the control system while a stop error exists in the
standby system, the control system is switched to the standby system and the both systems operate as standby systems.
In this case, eliminate error causes, and then power off and on or reset the CPU modules in the both systems.
The following table lists the operations of when both systems operate as standby systems.
Item
LED of the redundant function module
Special relay
System switching request
System switching disabled by online change
In a redundant system, the manual system switching is disabled during an online change. To disable the manual system
switching during an online change, the CPU module is set to the manual system switching disabled state before an online
change starts. After the online change is completed, it is set to the manual system switching enabled state.
If a communication with the engineering tool is interrupted due to communication cable disconnection or other causes during
an online change, the online change cannot be completed, and the CPU module remains in the manual system switching
disabled state. When the CPU module is in the manual system switching disabled state, the systems cannot be switched by
manual system switching or a system switching request from a network module.
If an online change has failed, refer to the following and take actions.
Page 199 Action for when an online change has failed
26 REDUNDANT FUNCTION
386
26.2 System Switching
BACKUP LED
SEPARATE LED
CTRL LED
SBY LED
SM1635 (Standby system judgment flag)
System switching request from a network module
System switching request by the SP.CONTSW instruction
System switching request from the engineering tool
Operation of both systems
Flashing (in backup mode)
Flashing (in separate mode)
Off
On
On
System switching disabled