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MITSUBISHI CNC
3. Installation
3.3 Calculating Heat Generation by C70
The ambient temperature inside the control panel storing the C70 must be suppressed to a C70 operating ambient
temperature of 55°C(131°F).
For the design of radiation from the storing panel, it is necessary to know the average power consumption (heating value)
of the devices and instruments stored in the control panel. Here the method of obtaining the average power consumption of
C70 is described. From the power consumption, calculate a rise in ambient temperature inside the control panel.
The power consuming parts of C70 are roughly classified into six blocks as shown below.
The following shows how to calculate the average power consumption in each block.
(1) Power consumption of the power supply module
The power conversion efficiency of the power module is approx. 70 [%], i.e., 30 [%] of the output power is
consumed by heating. As a result, 3/7 of the output power becomes the power consumption.
Therefore the calculation formula is as follows.
3
=
× (I
W
pw
7
I
: Current consumption of logic 5 VDC circuit of each module
5V
(2) Power consumption of a total of 5 VDC logic section of each module (including CPU module)
The power consumption of the 5 VDC output circuit section of the power module is the power consumption of
each module (including the current consumption of the basic base).
= I
× 5 [W]
W
5V
5V
(3) A total of 24 VDC average power consumption of the output module (power consumption for simultaneous ON
points)
The average power of the external 24 VDC power is the total power consumption of each module.
= I
× 24 x ratio of simultaneous ON [W]
W
24V
24V
I
: Average current consumption of internal consumption power supply of the output module 24VDC [A]
24V
It is not applied for the power supply unit which supplies 24VDC from outside and has no 24VDC output.
(4) Average power consumption due to voltage drop in the output section of the output module
(Power consumption for simultaneous ON points)
= I
× Vdrop × Number of output points × Simultaneous ON rate [W]
W
OUT
OUT
I
: Output current (Current in actual use) [A]
OUT
Vdrop : Voltage drop in each output module [V]
(5) Average power consumption of the input section of the input module (Power consumption for simultaneous ON
points)
= I
× E × Number of input points × Simultaneous ON rate [W]
W
IN
IN
I
: Input current (Effective value for AC) [A]
IN
E : Input voltage (Voltage in actual use) [V]
64
× 5) [W]
5v
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