SIGMATEK 074.00660, Power Installation Manual

Page: 28 / 98

28
Sigmatek FDD Sizes 7 to 9 Power Installation Guide
Figure 3-12 Enclosure having front, sides and top panels free to dissipate heat
Insert the following values:
T
int
40

C
T
ext
30

C
k 5.5
P 392.4 W
The minimum required heat conducting area is then:
= 7.135 m
2
(77.8 ft
2
) (1 m
2
= 10.9 ft
2
)
Estimate two of the enclosure dimensions - the height (H) and depth (D), for instance. Calculate the
width (W) from:
Inserting H = 2 m and D = 0.6 m, obtain the minimum width :
=1.821 m (71.7 in)
If the enclosure is too large for the space available, it can be made smaller only by attending to one
or all of the following:
•
Using a lower PWM switching frequency to reduce the dissipation in the drives
• Reducing the ambient temperature outside the enclosure, and/or applying forced-air cooling to
the outside of the enclosure
• Reducing the number of drives in the enclosure
• Removing other heat-generating equipment
Calculating the air-flow in a ventilated enclosure
The dimensions of the enclosure are required only for accommodating the equipment. The
equipment is cooled by the forced air flow.
Calculate the minimum required volume of ventilating air from:
W
H
D
A
e
392.4
5.5 40 30
–
 
---------------------------------
=
W
A
e
2HD –
H D +
--------------------------
=
W
7.135 2 2

0.6
  
–
2 0.6 +
-----------------------------------------------------
=
V
3kP
T
int
T
ext
–
---------------------------
=