6. Redundancy with NX3030 CPU
269
Interconnections between Half-Clusters and the Redundancy Control Panel PX2612
Figure 6-6 shows how the connections between PLCA, PLCB and PX2612 have to be made,
including the possibility to allow a CPU to switch off the other, which is necessary in exceptional
situations.
Two AL-2319 cables must be used for the synchronism and redundancy channels NETA and NETB.
One of these two cables interconnects the NX4010 NET 1 connector from each CPU (NETA
channel). The other cable interconnects the NX4010 NET 2 connector from each CPU (NETB
channel).
An AL-2317/A cable interconnects the NX4010 CONTROL connector from the PLCA to the
PX2612 CONTROL PLC A.
An AL-2317/B cable interconnects the NX4010 CONTROL connector from the PLCB to the
PX2612 CONTROL PLC B.
Besides this, it’s necessary to build a special power supply circuit in order to allow a CPU to switch
off the other in extreme cases.
For higher reliability, two separate 24V power supplies must be used, one for PLCA supply and other
for PLCB supply.
It can be observed that is necessary to use two external relays from the normally closed type (NC),
with current capacity to feed the NX8000. These relays must be dimensioned for a nominal current
around 2 A, however, a current inrush of around 10 A must be taken into account. Shunt diodes
connected to the NC relays solenoids must be used to protect the PX2612 NO relay contacts
Figure 6-6. Interconnections between PLCA, PLCB and PX2612
NET 1 NET 2
NX4010
CONTROL
NET 1 NET 2
NX4010
CONTROL
CONTROL CP A CONTROL CP B
PX2612
RLA GND RLB
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General