Rockwell Automation Allen-Bradley PowerFlex SCR, User Manual

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Installation/Wiring 1-17
PowerFlex SCR Bus Supply User Manual
Publication 20S-UM001G-EN-P
1000A SCR Bus Supply
Redundancy
It is not recommended to install parallel master SCR Bus Supplies. The
reason is that there is nothing to synchronize the SCR gate firing between
the precharge printed circuit boards in separate SCR Bus Supplies. Each
precharge board has circuitry designed to energize the DC bus, which has
little to no impedance to limit the inrush current. This DC bus charging
synchronization could lead to power device failure.
If redundancy of the SCR Bus Supply master is required by the application,
there are two options.
•
A microcontroller or other electronically or manually-controlled switch
or contact network can be used to reconfigure the wire harnesses
between the redundant master SCR Bus Supplies. Basically, one SCR
Bus Supply becomes the master and the other becomes the slave by the
logic selection of the controlling or steering network. One example of
numerous possible configurations is shown in
Figure 1.11 .
Figure 1.11 Basic Master/Slave Redundancy System Configuration
•
Although not recommended, synchronization differences might be
minimized by using the slower ramp time available in precharge printed
circuit boards with firmware version 1.22 (or later). The standard ramp
time is for the rise of DC bus to phase full on in approximately 0.2
seconds, while the slower ramp time will take approximately 1.3
seconds. This will help to limit the inrush current in the system.
For additional recommendations about SCR Bus Supply redundancy,
contact Rockwell Automation Technical Support.
Slave
Enable
Control Logic
* Only one Master enabled.
Slave Slave
Precharge
PCB
Master
Gate
PCB
Gate
PCB
Gate
PCB
Gate
PCB
Gate
PCB
Precharge
PCB
Master