70 Mechanical installation
Calculating the required static pressure difference
The required static pressure difference between the exit air duct and the inverter
installation room can be calculated as follows:
where
p
d
dynamic pressure
air density (kg/m
3
)
v
m
average air velocity in the exit duct(s) (m/s)
q rated air flow of the inverter (m
3
/s)
A
c
cross-sectional area of the exit duct(s) (m
2
)
Example:
The cabinet has 3 exit openings of 315 mm diameter. The rated air flow of the cabinet is
3760 m
3
/h = 1.0 m
3
/s.
A
c
= 3 • 0.315
2
• / 4 = 0.234 m
2
v
m
= q / A
c
= 1.0 / 0.234 = 4.3 m/s
p
d
= 0.5 • • v
m
2
= 0.5 • 1.1 • 4.3
2
= 10 Pa
The required pressure in the exit air duct is then, 1.5…2 • 10 Pa = 15…20 Pa, below the
pressure in the room.
More information: Contact ABB.
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