Nidec Commander C300 - Calculating the Air-Flow in a Ventilated Enclosure

Unidrive M / HS Frame 7 to 10 Power Installation Guide 37
Safety information Product information
Mechanical installation
Electrical installation Technical data UL listing information
Where:
V Air-flow in m
3
per hour (1 m
3
/hr = 0.59 ft
3
/min)
T
ext
Maximum expected temperature in C outside the enclosure
T
int
Maximum permissible temperature in C inside the enclosure
P Power in Watts dissipated by all heat sources in the enclosure
k Ratio of
Where:
P
0
is the air pressure at sea level
P
I
is the air pressure at the installation
Typically use a factor of 1.2 to 1.3, to allow also for pressure-drops in dirty air-filters.
Example
To calculate the size of an enclosure for the following:
• Three drives operating at the Normal Duty rating
• External EMC filter for each drive
• Braking resistors are to be mounted outside the enclosure
• Maximum ambient temperature inside the enclosure: 40 C
• Maximum ambient temperature outside the enclosure: 30 C
For example, dissipation of each drive: 101 W and dissipation of each external EMC filter: 6.9 W
(max).
Total dissipation: 3 x (101 + 6.9) = 323.7 W
Insert the following values:
T
int
40 C
T
ext
30 C
k 1.3
P 323.7 W
Then:
= 126.2 m
3
/hr (74.5 ft
3
/min) (1 m
3
/ hr = 0.59 ft
3
/min)
P
o
P
l
-------
V
31.3 323.7
40 30–
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=