Modular Redundant Power Supply Systems
AC-DC single output
Extremely high overall reliability results from connecting two power sources
so that one will continue to provide power to their load even if the other
becomes inoperative. Redundancy may be restored by replacing or repairing
the inoperative source while the system remains in operation. A redundant
power system should be used whenever the highest attainable reliability
is essential, as in communications, computer systems (data storage in particular),
process controls, utility and municipal systems, and security/safety systems.
System Description: Each Modular Redundant DC Power System consists
of three units: two identical power supplies connected to an Integration
Module by 24 long cables. The Integration Module includes the diodes
for isolating the power supply outputs, AC input switches, input fuses,
LED output present indicators, failure alarm circuits, and the
umbilical cables which plug into the power supplies. Connections for the
AC inputs, redundant DC output and failure alarm relays are on a screw terminal
Operation: The diodes isolate a faulted supply output from the system
output and pass only the output of the other power supply, without interruption
of system output power during the transition.
The output voltage of the Primary supply is set approximately 0.2 volt
higher than that of the Backup supply. Under this condition, the Backup
supplys series diode is not forward biased, and only the Primary supply
delivers current to the load. However, if the Primary supplys output
decreases by more than 0.2 volt, the situation is reversed, and only the
Backup supply delivers current. Each power supply includes an overvoltage
protection circuit, to assure that neither power supplys output will
significantly exceed the nominal output voltage rating under any condition,
including incorrect connection and adjustment.
Serviceability: Either power supply can be easily, safely and rapidly
changed while the other supply continues to provide uninterrupted power
to the load.
Alarm Circuits: The failure alarm circuits in the Integration Module
operate relays, the contacts of which are available to control external
failure alarms or other circuitry. The contact wiring of the two relays
is connected in cascade, to simulate a single set of Form C contacts which
switch if the output of either power supply decreases by more than 2.0 volts
(3.0 volts for outputs over 48 volts) from the nominal rating.
Input Redundancy: Two isolated sets of AC input connections are
provided, so that two independent sources of AC input power may be used,
to obtain the additional benefit of input power redundancy. By feeding one
input through a battery-backup power source (UPS), DC output power will
be maintained even if both AC power sources should fail.
Overvoltage Protection: Automatic recovery. Each power
supply contains an overvoltage protection circuit, to assure that neither
power supply output will significantly exceed the nominal output voltage
rating under any condition, including incorrect application and misadjustment.