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Using 1606 Power Supplies in N+1 and 1+1 Redundancy Applications
Summary
Using 1606 Power Supplies in N+1 and 1+1 Redundancy Applications
Answer
Two or more Power Supplies can be paralleled together in order to obtain a boost in system availability or output power. It is important to make a difference between these two as both have different wiring requirements and output different results.
- Parallel Use to Increase Output Power: two or more power supplies can be wired in parallel to increase the output power. For example: two 10A power supplies can be wired in parallel to obtain a combined 20A output. All power supplies must be adjusted to have the same output voltage, and is generally recommended to protect each power supply output (e.g. fuse, circuit breaker, redundancy modules, etc.) when more than 2 power supplies are used.
- Parallel use for Redundancy: two or more power supplies can be wired in parallel to increase system availability. For example: two 10A power supplies can be wired in parallel to obtain a 10A output, in the case one power supply fails the other can automatically sustain the load as a back-up.
The power supplies can be used in parallel for redundancy in two ways, 1+1 and N+1:
- 1+1 Redundancy: in this type of redundancy only two power supplies are used. One power supply is able to carry the entire load, a second power supply is used as the back-up device. Upon failure, the entire load is shifted to the second (or redundant) power supply.
- N+1 Redundancy: in this type of redundancy more than two power supplies are used. When both, system availability and increased output power are needed, this type of redundancy is used. “N” quantity of power supplies can be wired in parallel to increase output power, then one power supply would work as a back-up in case any of the “N” power supplies fails.
Please note, as shown in the picture above, it is essential to use a Redundancy Module to decouple power supplies from each other. This helps prevent the defective unit from becoming a load for the other power supplies, helping to maintain output voltage. Some 1606 power supplies include built-in redundancy and in such do not require an external redundancy module, refer to the section Power Supplies with Integrated Decoupling Function from the Switched Mode Power Supply Specifications Technical Data, publication 1606-TD002, for product selection.
For more details, refer to the Designing High-Availability 24VDC Systems, publication 1606-AT003.
Source: Rockwell Automation’s Technote database.
