Mitsubishi Q170MCPU, User Manual

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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) Total power consumption for logic 5VDC circuits of all modules
(including Motion controller)
This is a power to which each module consumes the current supplied by the
5VDC output circuit of the internal power supply.
(including the current consumption of the base unit.)
W
5V
= I
5V
5 [W]
I
5V
: Current consumption of logic 5VDC circuit of each module
(2) Power consumption of internal power supply
The power conversion efficiency of the internal power supply is approx. 80[%],
while 20 [%] of the output power is consumed as heat. As a result, 1/4 of the
output power is the power consumption.
Therefore the calculation formula is as follows.
W
PW
=
1
4 W
5V
[W]
I
5V
: Current consumption of logic 5VDC circuit of each module
(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 output module.
W
24V
= I
24V
24 Simultaneous ON rate [W]
I
24V
: Average current consumption of external 24VDC power supply [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
OUT
= I
OUT
Vdrop Number of outputs Simultaneous ON rate [W]
I
OUT
: Output current (Current in actual use) [A]
Vdrop : Voltage drop in each output module [V]