z
6.
LOADING
AND
INSTALLATION
/MELSEC-A
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
(hv
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
n
ci
1
li
3
I
3
I
-,
1
J
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