Nodes on one side of the power supply, Values to be calculated, Power supply calculation method – Yaskawa 260IF DeviceNet System User Manual

Page 76: Simple calculation from the graph, Calculation from the formula

7.1 Wiring Communications Power Supply

7-3

Nodes on One Side of the Power Supply

7.1.3 Methods for Deciding the Power Supply Positioning

Values to be Calculated

The power supply capacity required by each node and the voltage drop depending on the
length of the cable will determine whether or not the correct current can be supplied to each
node.

Calculate the following values.

• The current capacity required for each node.
• The distance from the power supply.

Power Supply Calculation Method

There are two methods for calculating the power supply for the trunk line.

Simple Calculation from the Graph

The simple calculation from the graph is based on the worst configuration, with maximum
voltage drop, as shown in the following diagram. The network will operate normally, there-
fore, if the conditions are met for a calculation from the graph.

Calculation from the Formula

The voltage drop is calculated from the transmission cable resistance and current consump-
tion.

The conditions may be met through the results of calculation from the fomula even if the
power supply specifications are not met through simple calculation from the graph. The net-
work will operate normally if conditions are met for either the calculation from the formula

Power Supply Tap

or T-branch Adapter

Communications

power supply

Node

Communications power

supply