Loading And Installation; Power Supply Module - Mitsubishi A2CCPU User Manual

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6. LOADING AND INSTALLATION
/MELSE
6.3 Calculation of Heat Generated by the
A2C
System
The operating temperature inside the panel to where the A2C
system is installed must be kept below 55' C . It is necessary to
include heat dissipation in the design of the installing panel
employing heat calculation of the system modules to be installed.
In this section, the calculation procedure of average power
consumption of the A2C system is explained. Perform heat
calculation using the result of power consumption calculation.
I
Average power consumption
I
Power is consumed by the following areas.
I
t -
1
module
current
(1) Power supply module
Approximately 70% of the power supply module current is
converted into power with the remaining 30% dissipated as
heat, i.e., 3/7 of the output power is used.
WpW
=
-
x
( h v
x
24)
(w)
3
7
hrv: Average current consumption of 24 VDC power supply for output
module internal consumption (current consumption of simultaneous
ON points)
...
Not applicable when 24 VDC is supplied from outside and the
power supply module does not have 24 VDC output.
(2) Total 24 VDC output module power consumption (with an
average number of points switched on)
24V is supplied to drive output devices.
Wzrv
=
1zrv
x
24
(w)
(3) Power consumption of output circuits (with an average
Wout = lout X Vdrop X average number of outputs on at one time (W)
where, lout = output current (actual operating current) (A)
number of points switched on)
Vdrop = voltage dropped across each output load (VI