Mitsubishi Electric M70V Series, Connection Manual

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3 Installation
MITSUBISHI CNC
88
Calculation example of panel internal heating value
(1) Calculation of unit heating value
Heating value (W)
Total heating value of units (W):
28W (= control unit + display unit + keyboard unit + operation panel I/O unit)
Total heating value (W) by machine input (D1):
5.6W (=24V (total heating value when the 32 points are simultaneously turned ON) × 7.3mA × 32)
... 24V (current consumption per point of the operation panel I/O unit DI) divided by 3.3k
Ω
≈
7.3mA
Total heating value W = 33.6W (28 + 5.6)
(2) Calculation of operation panel cooling capacity
Tolerance value for temperature rise (
⊿
t)
Panel internal temperature (according to each unit's specification) T
≤
55C°
Panel peripheral temperature (according to machine's specification) Ta
≤
45C°
Tolerance value for internal temperature rise
⊿
T = 10C° (T - Ta)
Heat radiation area (A)
The surface of the molded unit, which has lower radiation capacity than the base plate surface, should be
excluded for the heat radiation area in principle. The bottom of the operation panel, which has difficulty in
radiating due to the temperature distribution, should also be excluded for the heat radiation area in
principle.
Heat radiation area A = 0.71mm
2
(
≈
0.6 × 0.12 + 0.6 × 0.5 × 2 - (0.26 + 0.14) × 0.2 + 0.12 × 0.5 × 2)
(Top surface) (Front, rear surface) (Unit surface) (Both sides surface)
Operation panel cooling capacity (W1)
Calculate the cooling capacity to keep the temperature rise in the operation panel less than 10°C.
Cooling capacity W1 = 42.6W (6 × A ×
⊿
T)
(3) Comparison of heating value and operation panel cooling capacity
The operation panel cooling capacity is over the heating value, which presumed no need to install the heat
exchanger.
(4) Confirmation with the actual machine
The result of the calculation above is only a rough indication. The actual temperature rise may differ according
to the structure of the operation panel. Be sure to confirm the temperature rise value in the operation panel
when the machine is running.