Calculation Of Heat Generated By The Plc - Mitsubishi Q2ACPU User Manual

19. LOADING AND INSTALLATION

19.3 Calculation of Heat Generated by the PLC

The operating ambient temperature in the panel where the PLC is stored must be kept
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power consumption (heat generation) of the devices and machinery stored inside.In this
section, a method to obtain the average power consumption of the PLC system is
explained.
Calculate the temperature rise inside the panel from the power consumption.
Average Power Consumption
The power consuming parts of the PLC may be roughly classified into the following blocks:
(1)
(2)
or less.For heat dissipation design of the panel, it is necessary to know the average
Power consumption by power supply module
The power conversion efficiency of the power supply module is about 70%, and 30%
is consumed as heat generated, thus, 3/7 of the output power is the power
consumption.Therefore, the calculation formula is:
3
Wpw= {(I 5)+(I
5V 15V
7
I : Current consumption of 5VDC logic ladder circuit of each module
5V
I : Current consumption of 15VDC external power supply part of special function
15V
module
I : Average current consumption of 24VDC power supply for output module's
24V
internal consumption
(Current consumption equivalent to the points simultaneously ON)
...... Not applicable to a system where 24VDC is supplied externally and a
power supply module with no 24VDC output is used.
Total power consumption of 5VDC logic circuits of modules
The 5VDC output circuit power of the power supply module is regarded as the power
consumption of each module.
W =I 5 (W)
5V 5V
15)+(I 24)} (W)
24V
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