Examining Power Supply Connection Positions - Hitachi HIDIC EH-150 Applications Manual

12.4 Examining Power Supply Connection Positions

This section provides some suggestions for what can be done if the power consumption exceeds the maximum
allowable current value, using the following configuration as an example.
(Example 1) If the communication power supply is connected at the end of the network
Termination
resistor
Communication
power supply
Total power consumption value = 0.3 A + 0.1 A + 0.3 A + 0.1 A + 0.3 A + 0.2 A = 1.3 A
Maximum allowable current value = 1.03 A (from Figure 12.1)
From the summation above, it seems that the total power consumption value (1.3 A) is greater than the
maximum allowable current (1.03 A); i.e., the total power consumption value exceeds the maximum
allowable current.
(Action 1) Connect the communication power supply at the center of the network
Trunk line (thick cable)
Termination
resistor
Device
0.3A
Total power consumption value of section 1 = 0.3 A + 0.1 A + 0.3 A = 0.7 A
Total power consumption value of section 2 = 0.1 A + 0.3 A + 0.2 A = 0.6 A
Maximum allowable current value of section 1 = 2.01 A (from Figure 12.1)
Maximum allowable current value of section 2 = 2.01 A (from Figure 12.1)
In this configuration, the total power consumption is within the maximum allowable current value in
each section. Furthermore, it can be determined that power can be supplied to all the devices on the
network.
Trunk line (thick cable)
Device Device Device
0.3A 0.1A 0.3A
300m
Device Device
0.1A 0.3A
Communication
power supply
150 m (section 1)
12-4
Chapter 12 Communication Power Supply
Device Device Device
0.1A 0.3A 0.2A
Trunk line (thick cable)
Device Device Device
0.1A 0.3A 0.2A
150 m (section 2)
Termination
resistor
Termination
resistor