Parallel use for redundancy
Devices of the same type can be paralleled for redundancy to gain higher system availability. Redundant systems require a certain amount of extra power to support the load in case one power supply unit fails. The simplest way is to put two power supplies in parallel. This is called a 1+1 redundancy. In case one power supply unit fails, the other one is automatically able to support the load current without any interruption.
Please note: This simple way to build a redundant system does not cover failures such as an internal short circuit in the secondary side of the power supply. In such a case, the defective unit becomes a load for the other power supplies and the output voltage cannot be maintained any more. This can be avoided by utilizing redundancy modules, which have decoupling devices (diodes or MOSFETs) included.
Recommendations for building redundant power systems:
- Use separate input fuses for each power supply. A separate source for each supply when possible, increases the reliability of the redundant system.
- Set the power supply into “Parallel Use” mode.
- Monitor the individual power supply units. Therefore, use the DC-OK relay contact of the power supply.
- It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.
Wiring example
