6. LOADING AND INSTALLATION
MELSEC·A
6.3
Calculation
of
Heat
Generated
by
the
A2C System
The operating temperature inside the panel where the A2C system is in-
I
stalled 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.
IAverage power consumption I
Power is consumed by the following areas.
•
[DC
I
L--ir-
....
[DC
[
L_-i
r-
....
[DC
I
L_-i
r-
....
124v
24VDCline
$AC
Power
! ! !
.............
power
supply
Output Input
Special
supply
module
module
module
function
module
.
Reley
Input
current
Power
Transistors
(liN)
x E supply
L-
Outputcurrent
IInput
(Ioln) x Vdrop
cpu
Output
power
module
;eJ
current
~(IIN)
(Ioln)
AC E
~
LOAD
(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
41
output
power is used.
3
Wpm =
-;
x
(I24V
x 24) 0N)
124v
: 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.
W24V
=
124V
x 24 (W)
6-2
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