Calculating Heat Generation By Motion Controller - Mitsubishi Electric Melsec-Q172DCPU User Manual

3 DESIGN

3.3.2 Calculating heat generation by Motion controller

The ambient temperature inside the panel storing the Motion controller must be
suppressed to an ambient temperature of 55°C(131°F) or less, which is specified for
the Motion controller.
For the design of a heat releasing panel, it is necessary to know the average power
consumption (heating value) of the devices and instruments stored inside.
Here the method of obtaining the average power consumption of system is described.
From the power consumption, calculate a rise in ambient temperature inside the
control panel.
How to calculate average power consumption
The power consuming parts of the Motion controller are roughly classified into six
blocks as shown below.
(1) 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 consumption.
Therefore the calculation formula is as follows.
3
W = (I
PW 5V
7
I : Current consumption of 5VDC logic circuit of each module
5V
(2) Total power consumption for 5VDC logic circuits of all modules
(including CPU module)
The power consumption of the 5VDC output circuit section of the power supply
module is the power consumption of each module (including the current
consumption of the base unit).
W = I 5 [W]
5V 5V
(3) A total of 24VDC average power consumption of the output module
The average power of the external 24VDC power is the total power consumption
of each module.
W = I 24
24V 24V
I
: Average current consumption of 24VDC power supply for internal
24V
consumption of the output module [A]
(Power consumption for simultaneous ON points)
(4) Average power consumption due to voltage drop in the output
section of the output module
(Power consumption for simultaneous ON points)
W = I Vdrop
OUT OUT
I : Output current (Current in actual use) [A]
OUT
Vdrop : Voltage drop in each output module [V]
5) [W]
Simultaneous ON rate [W]
Number of outputs
3 - 12
Simultaneous ON rate [W]