User`s guide

5-10
In the following example, there are only two branches to check. Assume wire type is JY
(St) Y 2x2x0.8 and average wire temperature is 25°C. Thus, α = 1.
LPI-10
50m
50m 50m
20m
80m 50m
20m
5 nodes
100mA
2 nodes
100mA
3 nodes
100mA
2 nodes
100mA
2 nodes
100mA
5 nodes
100mA
2 nodes
100mA
In the upper branch,
(2
*
0.1A)(50m) + (5
*
0.1A)(100m) + (2
*
0.1A)(150m)
= 90 Amp*meters
≤ K
*
α
*
β = (530 Amp*meters)(1)(81%) = 430 Amp*meters
In the lower branch,
(5
*
0.1A)(20m) + (2
*
0.1A)(100m) + (3
*
0.1A)(150m) + (2
*
0.1A)(170m)
= 109 Amp*meters
≤ K
*
α
*
β = (530 Amp*meters)(1)(81%) = 430 Amp*meters
This network meets all system, transmission, and power specifications.
In many instances, the lengths of sub-branches can be ignored for this calculation,
reducing the effective d and improving performance.
To determine when the lengths of stubs or sub-branches can be ignored for power
calculation, begin at the ends of the branches and move toward the LPI-10 module.
Upon arriving at a branching point, calculate the sum of products (I
1*
d
s1
+ I
2*
d
s2
+ .
. . )
for every sub-branch where I is the application current of a node and d
s
is the
distance of that node from the branching point. Then ignore the lengths of all the sub-
branches except for the sub-branch with the largest sum of products. Repeat this
procedure until the effective network looks like a bus (see Step Three of Example 1).
Note that this simplification may be used only for power considerations. For
transmission specifications, the actual total wire length and maximum distance node-
to-node must be used.