HUST H2N Connecting Manual
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3.3 Thermal Design in the Cabinet
The cabinet for the control unit must be a closed structure, and the temperature rise
within the cabinet must be 10
o
C or less than the ambient temperature. When
designing a metal cabinet for a CNC unit, two factors must be considered, which are
the heat source and the radiation area. For a CNC unit, the user cannot do too much
to change the heat source. Therefore, the one thing that the user can do in controlling
the temperature rise is the radiation area. The allowable temperature rise inside a
metal cabinet can be estimated as follows:
1. With a cooling fan, the allowable temperature rise is 1
o
C/6 W/1 m
2
.
2. Without a cooling fan, the allowable temperature rise is 1
o
C/4 W/1 m
2
.
This means that a cabinet with a radiation area of 1 m
2
and a cooling fan will have an
internal temperature rise of 1
o
C when a heating unit of 6 W (4W without a cooling)
is inside the cabinet. The radiation area of a cabinet is the entire surface area of the
cabinet minus the area contacting the floor.
Example 1 (with a cooling fan):
A cabinet has a 2 m
2
radiation area with a temperature rise of 10
o
C. The maximum
allowable heat value inside the cabinet is 6 W x 2 x 10 = 120 W. Therefore, the heat
generated inside the cabinet must be kept less than 120 W. If the heat generated is
120 W or more in the cabinet, some other cooling devices, such as cooling fins, must
be incorporated in the unit.
Example 2 (without a cooling fan):
A cabinet has a 2 m
2
radiation area with a temperature rise of 10
o
C. The maximum
allowable heat value inside the cabinet is 4 W x 2 x 10 = 80 W. Therefore, the heat
generated inside the cabinet must be kept less than 80 W. If the heat generated is 80
W or more in the cabinet, some other cooling devices, such as fan, or cooling fins,
must be incorporated in the unit.
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