Rtu I/O Expansion - Power Considerations - Motorola V186 - Cell Phone - GSM System Planner Manual

RTU I/O Expansion - Power Considerations

When planning a co-located multi-I/O expansion frame configuration (where all frames
are located in the same enclosure or 19" rack), it is possible to cascade the power supplies
of the expansion frames to the power supply in the main frame. In the system design
stage (before ordering), it is critical to calculate the maximal accumulated power
consumption from the main frame power supply (or from a power supply located on an
expansion frame which is not an expansion power supply) to make sure it is not
overloaded. It is also critical to consider the voltage drop due to the cascading of power
supplies.
Power Consumption
The first step in the design is to calculate the number of expansion frames that can be
cascaded per the power supply specifications.
The following power consumption information should be accumulated for the RTU:
Maximal accumulated power consumption of the main frame (CPU, I/O modules,
24 V floating power supplies on modules, radio, etc.)
Maximal accumulated power consumption of the each expansion frame (expansion
module, I/O modules, floating power supplies on modules)
Note: The power consumption information is described in the ACE3600 Owner's Manual
and in this document in Appendix C: ACE3600 Maximum Power Ratings.
The accumulated power consumption from the main power supply (located in the main
frame) should not exceed its maximum current output specifications. Consider the
following example:
An expanded RTU requires five expansion frames.
The accumulated power consumption of all frames exceeds the main power supply
specifications.
The accumulated power consumption of the main frame and the four first frames
exceeds the main power supply specifications.
The accumulated power consumption of the main frame and the three first frames
does not exceed the main power supply specifications.
This means that from the power consumption perspective the first three expansion
frames can be cascaded to the power supply in the main frame, the expansion power
supply on the fourth expansion frame should be replaced with AC or DC power
supply option and the fifth expansion power supply can be cascaded to this added
power supply.
Voltage Drop
The second step is to calculate the number of expansion power supplies that can be
cascaded per the allowable input voltage to the expansion power supply.
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