1 Publication 1762-UM001D-EN-P - March 2004
Appendix
F
System Loading and Heat Dissipation
System Loading Limitations
When you connect MicroLogix accessories and expansion I/O, an
electrical load is placed on the controller power supply. This section
shows how to calculate the load and validate that the system will not
exceed the capacity of the controller power supply.
The following example is provided to illustrate system loading
validation. The system validation procedure accounts for the amount
of 5V dc and 24V dc current consumed by controller, expansion I/O,
and user-supplied equipment. Use the System Loading Worksheet on
page F-3 to validate your specific 24-point controller configuration.
Use the System Loading Worksheet on page F-8 to validate your
specific 40-point controller.
Current consumed by the processor, memory modules, and the
real-time clock modules has already been factored into the
calculations. A system is valid if the current and power requirements
are satisfied.
System Loading Example Calculations (24-Point Controller)
Current Loading
Table F.1 Calculating the Current for MicroLogix Accessories
Catalog Number Device Current Requirements Calculated Current
at 5V dc (mA) at 24V dc (mA) at 5V dc (mA) at 24V dc (mA)
1761-NET-AIC
(1)
when powered by the base unit communications
port, selector switch in the up position
0 120 0 120
Subtotal 1: 0 120
(1) This is an optional accessory. Current is consumed only if the accessory is installed.
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