Understand System Planning - Allen-Bradley FLEX Ex 1797-PS2E2 Installation Instructions Manual

4 FLEX Ex Power Supply
The 1797-PS2E2 is a 24V dc in/quad-Ex dc out power supply in an
flame-proof enclosure with increased safety input and output terminations.
The 24V dc gland is an M20 x 1,5 and can accept a cable from 6...12 mm
(0.267...0.472 in.) in diameter. The Ex outputs are M16 x 1,5 and can accept a
cable from 4...8 mm (0.157...0.315 in.) in diameter.
Features include the following:
• 24V dc supply source
• Four channels, 8.5 W output each channel
• Dual power feeds for source input redundancy
• Outputs are IS galvanically isolated from the source
• All channels are independently IS limited

Understand System Planning

Part of system planning is determining what modules are needed for the
application, how many power supplies are needed, how to best partition the
system, and where to locate the system cabinets.
A key task in the development cycle is determining the number of power
supply outputs (thus power supplies) you will need. In the following example,
you will need 11 power outputs if you are using the fiber hub, which requires
8.5 W.
Modules
Fiber hub
a
Two ControlNet dapters
Two analog inputs
Two analog outputs
Each power supply has four independent IS-power outputs capable of 8.5 W
each. In the above example, we required 11 IS-power outputs so 3 power
supplies were sufficient.
Publication
1797-IN535F-EN-P - August 2017
Requires Modules
8.5 W Two thermocouple inputs
8.5 W each Two digital outputs
7.5 W each Three NAMUR digital inputs
6.3 W each Two counter inputs
Requires
1.6 W each
7.5 W each
2.8 W each
4.25 W each