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11. CHARACTERISTICS
(2) Heat dissipation area for enclosed drive unit
The enclosed control box (hereafter called the control box) which will contain the drive unit should be
designed to ensure that its temperature rise is within
10
(50 )
at the ambient temperature of
40
. (With a 5 (41 ) safety margin, the system should operate within a maximum 55 (131 )
limit.) The necessary enclosure heat dissipation area can be calculated by Equation 11.1:
P
A
KT
.............................................................................................................................................(11.1)
where, A : Heat dissipation area [m
2
]
P : Loss generated in the control box [W]
T : Difference between internal and ambient temperatures [ ]
K : Heat dissipation coefficient [5 to 6]
When calculating the heat dissipation area with Equation 11.1, assume that P is the sum of all losses
generated in the enclosure. Refer to Table 11.1 for heat generated by the drive unit. "A" indicates the
effective area for heat dissipation, but if the enclosure is directly installed on an insulated wall, that
extra amount must be added to the enclosure's surface area.
The required heat dissipation area will vary wit the conditions in the enclosure. If convection in the
enclosure is poor and heat builds up, effective heat dissipation will not be possible. Therefore,
arrangement of the equipment in the enclosure and the use of a fan should be considered.
Table 11.1 lists the enclosure dissipation area for each drive unit when the drive unit is operated at
the ambient temperature of 40
(104 ) under rated load.
(Outside)
(Inside)
Air flow
Fig. 11.2 Temperature distribution in enclosure
When air flows along the outer wall of the enclosure, effective heat exchange will be possible, because
the temperature slope inside and outside the enclosure will be steeper.