For applications requiring a high level of availability, the consequences of a power supply failure can be very serious: loss of production in industry, safety problems in infrastructure (e.g. lighting in tunnels).

Connecting power supplies in parallel (redundancy) is one way of ensuring continuity of service, as the probability of a failure affecting two power supplies simultaneously is very low.

The part number of the redundancy module is ABL8RED24400.
This redundancy needs to be provided by a module which is itself very rugged and which improves operation:

Correct operation is not guaranteed if a power supply other than an ABL8RPx24xx0 or ABL8WPS24x00 is used.

The choice of power supply depends on the nominal current to be supplied.
Direct connection of power supplies in parallel (without a redundancy module) has the following disadvantages:

• If one of the outputs on the two power supplies short-circuits, no voltage is delivered to the control system.
• No signal is given if one of the two power supplies shuts down, meaning that no voltage is delivered if the second power supply fails.

The redundancy module offers the following advantages:

• Electrical isolation of the two power supplies
• Local and remote indication (via LED and output contact respectively) as soon as a fault occurs, allowing maintenance work to be carried out while maintaining supply of the 24V
• Reliability is 5 times higher than for power supplies (MTBF)

See attached catalogue excerpt for further information.

Note:
The power supply primaries can be connected in parallel to the same network or connected to two separate networks (such as an emergency supply, for example).

Note:
The redundancy module can be used to connect two power supplies with a maximum rating of 20 A in parallel. To connect two 40 A ABL8WPS24400 power supplies, two ABL8RED24400 redundancy modules must be used.

Released for:Schneider Electric UK