Panasonic S-LINK V, User Manual

Page: 24 / 182

24
Chapter 1
Power Supply Capacity of System
Necessity of Local Power Supply Unit
The 24V DC power supply unit that drives the system uses either the centralized power supply method (use of
only one power supply unit) or the decentralized power supply method (use of additional local power supply unit)
to supply power to each unit.
At first, calculate the total current consumption value (sum total of current consumption values of all units ‘+’ sum
total of load current values of I/O devices).
After that, from the obtained calculation result, cable length, and conductor resistance, calculate the voltage
drop value, and determine the voltage to be supplied to each unit.
If the voltage supplied to each unit is above the rated voltage (22.8V or more for the controller, 21.6V or more for
the I/O unit), you can design the system using the centralized power supply method.
If the voltage supplied to a unit is out of the rated voltage range, connect a local power supply unit, and use the
local power supply method.
Designing of system using local power supply method
To use a local power supply unit, turn on the local power supply unit first, and then turn on the main
power supply unit, or turn on these power supply units at the same time.
If the main power supply unit is turned on first, the system may not operate properly.
CAUTION
In the following cases, connect a local power supply unit:
● The communication distance is too long, and voltage drop is too large.
For this reason, it is not possible to supply the rated voltage to the I/O units.
● A 2-core cable is used for connection of the I/O unit (for the D-G line only).
● The main power supply unit and the local power supply unit should be the small capacity type.
● An I/O device that generates a large noise should be used.
<Reference value>
Conductor cross section (mm
2
) Conductor resistance (Ω/m)
0.3 Approx. 0.065
0.5 Approx. 0.040
0.75 Approx. 0.025
1.25 Approx. 0.015
2.0 Approx. 0.010
Notes: 1) The conductor resistance values shown in the above table are reference values.
To determine the conductor resistance values for the actual cables, contact the cable manufacturer.
2) The conductor cross section of the exclusive 4-core flat cable should be 0.5mm
2
.
To determine whether a local power supply unit is necessary, refer to the flowchart shown on the next page.