Calculation Of Airflow Required For Cooling The Sab; Acoustic Noise; Vibration And Shock; Operating Environment: General - Danfoss VLT ISD 510 Design Manual

System Integration
4.2.3.2 Calculation of Airflow Required for
Cooling the SAB
The airflow required to cool the SAB (or multiple SABs in 1
cabinet) can be calculated as follows:
1. Determine the power loss at maximum output for
all SABs.
2. Add the power loss values of all SABs that can
operate at same time. The resulting sum is the
heat Q to be transferred. Multiply the result with
the factor f, read from Table 4.2.
For example, f = 3.1 m
3. Determine the highest temperature of the air
entering the enclosure. Subtract this temperature
from the required temperature inside the
enclosure, for example 45 °C (113 °F).
4. Divide the total from step 2 by the total from
step 3.
The calculation is expressed by the following formula:
f x Q
V =
T – T
i A
V
3
Airflow in m /h
f
Factor in m 3 x K/Wh (calculated as: cp x ρ (specific
heat of air x density of air))
Q Heat to be transferred in W
Temperature inside the enclosure in °C
T
i
Ambient temperature in °C
T
A
Table 4.1 Formula Abbreviations
NOTICE
Specific heat of air (cp) and density of air (ρ) are not
constants, but depend on temperature, humidity, and
atmospheric pressure. Therefore, they depend on the
altitude above sea level.
Table 4.2 shows typical values of the factor f, calculated
for different altitudes.
Altitude Specific heat of air (cp)
[m] [kJ/kgK]
0 0.9480
500 0.9348
1000 0.9250
1500 0.8954
2000 0.8728
2500 0.8551
3000 0.8302
3500 0.8065
Table 4.2 Factor f, Calculated for Various Altitudes
MG36C102
Design Guide
3
x K/Wh at sea level.
Density of air (p) Factor (f)
[kg/m 3 ] [m 3 K/Wh]
1.225 3.1
1.167 3.3
1.112 3.5
1.058 3.8
1.006 4.1
0.9568 4.4
0.9091 4.8
0.8633 5.2
Danfoss A/S © 08/2017 All rights reserved.
Example
How to calculate the airflow required to cool 2 SABs (with
heat losses of 295 W and 1430 W) running simultaneously,
mounted in an enclosure with an ambient temperature
peak of 37 °C, and an installation altitude of 500 m:
1. The sum of the heat losses of both frequency
converters (295 + 150 W) = 445 W.
2.
Multiply 445 W by 3.3 m
K/h.
Subtract 37 °C from 45 °C = 8 °C (=8 K).
3.
4.
3
Divide 1468.5 m x K/h by 8 K = 183.56 m
If the airflow is required in CFM (cubic feet per minute),
3
use the conversion 1 m /h = 0.589 CFM. For this example,
183.56 m 3 /h = 108.1 CFM.

4.2.4 Acoustic Noise

Acoustic noise from the SAB comes from 3 sources:
•
DC-link (intermediate circuit) coils
•
RFI filter choke
•
Internal fans
The acoustic noise ratings shown in Table 4.3 were
measured 1 m from the unit.
50% fan speed [dBA]
SAB 51
Table 4.3 Acoustic Noise Ratings

4.2.5 Vibration and Shock

The SAB is tested according to a procedure based on the
IEC 60068-2-6. The SAB complies with requirements that
correspond to these conditions when the unit is wall or
floor-mounted, as well as when mounted within panels, or
bolted to walls or floors.

4.3 Operating Environment: General

4.3.1 Aggressive Atmospheres

4.3.1.1 Gases

Aggressive gases, such as hydrogen sulphide, chlorine, or
ammonia can damage SAB electrical and mechanical
components. Contamination of the cooling air can also
cause the gradual decomposition of PCB tracks and door
seals. Aggressive contaminants are often present in sewage
treatment plants or swimming pools. A clear sign of an
aggressive atmosphere is corroded copper.
In aggressive atmospheres, restricted IP enclosures of
cabinet are recommended.
3 x K/Wh = 1468.5 m 3 x
3
/h.
Full fan speed [dBA]
60
35
4 4