Example: Current Consumed by a Remote Configuration

Introduction

This example is for a remote configuration (TM5 System Transmitter module and TM7 System expansion I/O blocks). From this example, you should be able to make the calculations necessary for your TM7 System.

All current consumption values are documented in the chapter TM7 Safety-Related System Power Consumption Tables.

Planning Example

This configuration example includes:

oThe TM5SBET7 transmitter module.

oSome expansion blocks:

oTM7BDI8B

oTM7BDI16B

oTM7SDM12DTFS

oTM7BDM16B

oTM7BDO8TAB

oTM7SDI8DFS

oTM7BAI4CLA

oTM7BAO4CLA

oAssumptions used for the purposes of calculating the consumption of this example:

TM7BDI8B: This block is connected to the power supply to distribute 8000 mA to the 24 Vdc I/O power segment.

The current to supply the electronic sensors of this example has been estimated at 25 mA per sensor, or 200 mA total for the block.

TM7BDI16B: The current to supply the electronic sensors of this example has been estimated at 37.5 mA per sensor, or 500 mA total for the block.

TM7SDM12DTFS: The sum of the current draw for all outputs connected to the block is not more than 2500 mA at any given time.

The current to supply the electronic sensors of this example has been estimated at 50 mA per sensor, or 400 mA total for the block.

TM7BDM16B: The sum of the current draw for all outputs connected to the block is not more than 2000 mA at any given time.

The current to supply the electronic sensors of this example has been estimated at 25 mA per sensor, or 200 mA total for the block.

TM7BDO8TAB: This block is connected to the power supply to distribute 8000 mA to the 24 Vdc I/O power segment.

Only 6 of the outputs are active at any given time, and that the maximum current draw of any given output is 1000 mA, or 6000 mA total for the block.

TM7SDI8DFS: The consumption of the block is 150 mA (from main power supply). The consumption of the electronics of the block is 168 mA (from I/O power supply).

TM7BAI4CLA: The consumption of the block is 38 mA (from main power supply).

The consumption of the electronics of the block is 125 mA (from I/O power supply).

TM7BAO4CLA: The consumption of the block is 38 mA (from main power supply).

The consumption of the electronics of the block is 188 mA (from I/O power supply).

The following graphic shows the example configuration connected to the power supplies PS1 and PS2:

 

PS1   External isolated main power supply, 24 Vdc

PS2   External isolated I/O power supply, 24 Vdc

The following table shows the current supplied and consumed in mA on the TM7 power bus and the 24 Vdc I/O power segment:

Current Consumed on the TM7 Power Bus

The TM5SBET7 generates 304 mA on the TM7 power bus to supply expansion blocks. The TM7 power bus begins with the TM7BDI8B block and terminates with the TM7BAO4CLA expansion block.

The total current consumed on the TM7 power bus is 538 mA and exceeds the 304 mA capacity of the segment.

Supplement the TM7 power bus by adding a TM7SPS1A between the TM7BDM16B and TM7BDO8TAB blocks.

The following table shows the current supplied and consumed in mA on the TM7 power bus:

The total current consumed on the TM7 power bus is 538 mA, and does not exceed the 1054 mA capacity of the TM7 power bus.

The following graphic shows the example configuration (with the PDB) connected to the power supplies PS1 and PS2:

 

PS1   External isolated main power supply, 24 Vdc

PS2   External isolated I/O power supply, 24 Vdc

For important information concerning power supply connections, TM5SBET7, PDB, I/O Block, refer to Wiring the Power Supply.

The next step is to calculate the current consumed on the 24 Vdc I/O power segment to validate the configuration of this example.

Current Consumed on the 24 Vdc I/O Power Segment

In this example,

oThe first 24 Vdc I/O power segment begins with the TM7BDI8B and finishes with the TM7BDM16B. The capacity of this segment is limited to 8000 mA.

oThe second 24 Vdc I/O power segment begins with the TM7BDO8TAB and finishes with the TM7BAO4CLA. The capacity of this segment is limited to 8000 mA.

The following table shows the current supplied and consumed in mA on the 24 Vdc I/O power segment:

The total current consumed on the first 24 Vdc I/O power segment is 6063 mA and does not exceed the 8000 mA capacity of this segment.

The total current consumed on the second 24 Vdc I/O power segment is 6564 mA and does not exceed the 8000 mA capacity of that segment.

NOTE: To create a new segment, connect a separate external isolated power supply to 24 Vdc Power In connector of the block that would otherwise cause the current limitation to be exceeded.