The System Power Supply (Dual DC/DC) provides 12 VDC LocalBus power to the I/O subsystem when it is operated on either 12 VDC or 24 VDC input power. In addition, it converts some input power to supply the requirements of the controller if it is mounted directly to the left of the controller or on the right slot of a second 2-wide power/controller carrier.
Supplying System Power to the I/O
You can add a second system power supply to provide I/O power redundancy. The second supply mounts in the right slot of the second 2-wide power/controller carrier, as shown in the following figure. Power this supply from a separate bulk power supply to provide power if the primary bulk supply fails.
Supplying Redundant Power to the Controller
To provide redundant power to the controller, install a secondary system power supply in the right slot of the second power/controller carrier as shown in the preceding image. You must mount the secondary supply in the right slot to provide power to the controller.
The power conversion from 12 VDC is done inside of the system supply. Because of this, you could decide that it is acceptable to supply power to both system supplies from a single bulk supply if your application can support that single point of failure.