
B-63404EN/03 CONNECTION 1.CONNECTING DeviceNet FUNCTIONS
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When current consumption is uneven on either side of the power supply unit (example 3)
The following shows an example where thick cable having a total
length of 240 m is used for the power supply, and the communications
power supply is located by moving it slightly away from the center of
the network.
If the total current consumption is uneven on either side of the power
supply unit and is insufficient even if the communications power
supply is located in the center of the network, the current
consumption conditions are sometimes satisfied by moving the power
supply unit slightly.
In this example, the current consumptions of each node are assumed
to be as shown in the following figure.
When the power supply unit is located in the center:
Total length of power supply line (left side) = Total length of power
supply line (right side) = 120 m
Total current consumption (left side) = 1.1A + 1.25A + 0.5A = 2.85A
Total current consumption (right side) = 0.25A+0.25A+0.85A=1.35A
Maximum current (left side) calculated from the table for thick cable
= Approx. 2.5 A
Maximum current (right side) calculated from the table for thick cable
= Approx. 2.5 A
(The above values are calculated by linear approximation between
100 and 150 m.)
The relationship becomes "total current consumption (left side) is
greater than the maximum current (left side)," so it can be seen that
the current consumption is insufficient on the left side.
To remedy this, move the position of the power supply unit to the left
as shown in the figure below.
Total length of power supply line (left side) = 100 m
Total length of power supply line (right side) = 140 m
Terminator
Node Node
Terminator
Power supply tap
NodeNode
120m
Trunk line (5-lead cable)
0.85A0.25A
1.25A1.1A
120m
Within
3 m
Node
0.5A
Node
0.25A
Communications
power supply
Terminator
Node Node
Terminator
Power supply tap
NodeNode
120m
Trunk line (5-lead cable)
0.85A0.25A
1.25A1.1A
100m
Within
Node
0.5A
Node
0.25A
Communications
power supply