Calculation of the total current consumption

In the following example, the AC500 control system consists of

• the CPU PM581-ETH
• the 4 communication modules CM572-DP (1x), CM575-DN (1x), CM577-ETH (1x), CM578-CN (1x)
• the 7 expansion modules DC522 (1x), DC523 (1x), DC532 (1x), AX521 (1x), AX522 (1x), AI523 (1x), AO523 (1x)
• as well as the required Terminal Bases and Terminal Units

Remark: Because of the high total current consumption of the digital I/O modules (from UP = 24 DC), the supply is divided up into several electric circuits fused separately. The maximum permitted total current over the supply terminals of the I/O Terminal Units is 8 A.

The total current can be calculated as follows:

ITotal = ICLUSTER + IUP

with the following assumptions

ICLUSTER = ICPU + II/O-Bus + IC1 + IC2 + IC3 + IC4 (CPU + communication modules + I/O-Bus)

II/O-Bus = Number of expansion modules x Current consumption through the I/O-Bus per module

and

IUP = IUP1 + ILOAD1 + IUP2 + ILOAD2 + IUP3 + ILOAD3 + IUP4 + ILOAD4 + IUP5 + ILOAD5 + IUP6 + ILOAD6 + IUP7 + ILOAD7

If one assumes that all outputs are switched on and are operated with their maximum permitted load currents (under compliance with the maximum permitted currents at the supply terminals), then the following values are the result for the example shown above:

	ICPU	ICx	II/O-Bus	IUPx	ILOADx
CPU part
PM581-ETH	0.110 A	-	-	-	-
CM572-DP	-	0.050 A	-	-	-
CM575-DN	-	0.050 A	-	-	-
CM577-ETH	-	0.085 A	-	-	-
CM578-CN	-	0.050 A	-	-	-
I/O part
AI523	-	-	0.002 A	0.150 A	-
AO523	-	-	0.002 A	0.150 A	0.160 A
AX521	-	-	0.002 A	0.100 A	0.080 A
AX522	-	-	0.002 A	0.100 A	0.080 A
DC522	-	-	0.002 A	0.050 A	8.000 A *)
DC523	-	-	0.002 A	0.050 A	8.000 A *)
DC532	-	-	0.002 A	0.050 A	8.000 A *)
Sums	0.110 A	0.235 A	0.014 A	0.650 A	24.320 A
	-—————————-V——————————/			-————–V—————-/
	ICLUSTER = 0.359 A			IUP = 24.970 A
	-—————————————V—————————————/
	ITotal = 25.329 A
*) The maximum permitted total current over the supply terminals of the I/O Terminal Units is 8 A.