ABB ACS880-07 Series - Calculating the Required Static Pressure Difference

Calculating the required static pressure difference
The required static pressure difference between the exit air duct and the drive installation
room can be calculated as follows:
Δp
s
= (1.5…2) · p
d
where
p
d
= 0.5 · ρ · v
m
2
v
m
= q / A
c
Dynamic pressurep
d
Air density (kg/m
3
)ρ
Average air velocity in the exit duct(s) (m/s)v
m
Rated air flow of the drive (m
3
/s)q
Cross-sectional area of the exit duct(s) (m
2
)A
c
Example
The cabinet has 3 exit openings of 315 mm diameter. The rated air flow of the cabinet is
4650 m
3
/h =1.3 m
3
/s.
A
c
= 3 · 0.315
2
· π / 4 = 0.234 m
2
v
m
= 1.3 / 0.234 = 5.5 m/s
p
d
= 0.5 · ρ · v
m
2
= 0.5 · 1.1 · 5.5
2
= 17 Pa
The required pressure in the exit air duct is then, 1.5…2 · 17 Pa = 26…34 Pa, below the
pressure in the room.
84 Mechanical installation
4