Alpha Technologies CFR Redundant Control Unit - Manual (Page 3)

1
1 Introduction
1.1 The Alpha Redundant Control Unit (RCU)
Alpha’s Redundant Control Unit (RCU) provides a dual–redundant configuration, ensuring
power is always supplied to the critical load. Both input voltages are monitored, so if power is
lost at input 1, the RCU transfers to input 2. Input 1 is the primary source of power so the RCU
automatically returns to it when power is restored. Before transferring, it waits about 1 minute
to allow input voltage and frequency to stabilize.
The RCU has two contactors, one for each power source. They both cannot be on at the same
time. If there is a failure in either contactor or the control logic, the Type C alarm contact on the
rear panel is activated and the “Red Alert” LED turns on. Alarm conditions are: logic failure;
Contactor 1 or 2 fails to open; Contactor 1 or 2 fails to close or open internal fuses. The front
panel LEDs shows the RCU’s status.
Purpose: Describes the operation of Alpha’s Redundant Control Unit (Figure
1.1)
O utp ut In puts
C o n ta cto r 2
L og ic
C o n ta cto r 1
P rim ary
S econ d ary
Figure 1.1
RCU Operating Diagram