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becomes active. Redundancy switchover occurs within 10 msec of loss of active CPU
control (i.e. if the active CPU does not reset the watchdog for more than 5 msec, if the
active CPU resets, or if the active CPU is removed from its slot.)
The ACE3680 CPUs include an internal Ethernet 100 Mb/s port used for redundancy only.
This interconnection (via motherboard) between the active and standby CPUs enables the
active CPU to continuously synchronize the standby CPU's database and clock.
I/O expansion is supported by the redundant CPU configuration. For details, see the ACE3600
System Planner, but are limited to 12 expansion frames. The primary CPU and secondary CPU
must be connected to the I/O expansion LAN switch(es). The I/O expansion frames must be
connected to the LAN switch (note that with redundant CPUs even a single I/O expansion
frame requires an expansion LAN switch module.) I/O modules in the main rack are not
affected by redundancy switchover. I/O modules in expansion racks enter PDV/KLV mode
until connection is established with the new active CPU (between 5-15 seconds.)
For information on using the Redundant CPU feature, see the RTU Redundancy section of the
ACE3600 STS Advanced Features manual.
Redundant Power Supply
Redundant power supplies are used to ensure a continuous supply of the required RTU
voltages, in the event that one power supply fails. When one of the power supplies fails, the
user application program can sense it and send an alarm to the control center. Both the primary
and secondary power supplies must be of the same type. Only the primary power supply is
configured in the STS and the configuration is duplicated to the secondary power supply.
The primary CPU (leftmost CPU slot) communicates with the primary power supply, and the
secondary CPU (rightmost CPU slot) communicates with the secondary power supply.
Redundant Power Supply Behavior
•
The primary power supply always has priority. The secondary power supply takes over if
the primary is absent, or if the power level of the primary is lower than the secondary by
0.4V.
•
When power returns to the primary power supply, the secondary gives up the control.
Note: The power to the motherboard is initially provided by the primary power supply. In a
system with I/O expansion and redundant power supplies, the power distribution does not
support the redundancy. Therefore it is recommended that each expansion frame use its own
power supply (not an expansion power supply).
Redundant CPU and Power Supply RTU Configuration
By default, the Redundant CPU and Power Supply option includes a special frame/
motherboard designed for dual power supply, dual CPU, and four I/O slots. In addition, two
CPU3680 modules, one 12V power supply and one blank power supply module are provided.
It is possible to replace the default single 12V power supply with any of the power supply
options (AC, AC with charger, 18-72 VDC, etc.) except the low-tier power supply.
Appendix E: CPU and Power Supply Redundancy
E-3
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