User`s manual

Calculating heat generation of programmable controller Installation
MELSEC System Q, Hardware 9 – 7
9.3 Calculating heat generation of programmable controller
The ambient temperature inside the panel storing the programmable controller must be sup-
pressed to an ambient temperature of 55 °C. The heat generated by the system should be lead
off by ventilation devices.
Following figure shows the power consuming parts of the programmable controller:
Power consumption of power supply module
The power conversion efficiency of the power supply module is approx. 70 %, while 30 % of the
output power is consumed as heat. As a result, 3/7 of the output power is the power consump-
tion.
The calculation formula is as follows:
W
PW
= 3/7 (I
5V
x 5 V) [W]
W
PW
: Heat capacity of the power supply
I
5V
: Current consumption of logic 5 V DC circuit of each module [A]
Total power consumption for 5 V DC logic circuits of all modules
The power consumption of the 5 V DC output circuit section of the power supply module is the
power consumption of each module (including the current consumption of the base unit) mul-
tiplied by the 5 V power supply.
W
5V
= I
5V
x 5 V [W]
A total of 24 V DC average power consumption of the output modules
The sum of all currents, flowing into the output moduls with all outputs switched on, multiplied by
the voltage of the external power supply results in the total power consumption at 24 V DC .
W
24V
= I
24V
x 24 V x Simultaneous ON rate [W]
E000305C
Fig. 9-4: Calculation of the power consumption
AC power supply
Power
supply
module
CPU
I
5V
External
power
supply
24 V DC
I
24V
Power supply
24 V DC
Power supply 5 V DC
Link
module
Relay/
Transistor
Output current
I
OUT
x V
drop
Input
module
Input current
I
IN
x V
IN
Output
current
I
OUT
Load
Input
current
I
IN
AC
DC
AC
DC
Intelligent
function
module
AC
DC
Output
module
Power supply
module