Motor-Generated Overvoltage; Acoustic Noise; Vibration And Shock; Aggressive Atmospheres - Danfoss VLT AQUA Drive FC 202 Design Manual

System Integration
Table 3.1 shows typical values of the factor f, calculated for
different altitudes.
Altitude
3 3
[m]
0
500
1000
1500
2000
2500
3000
3500
Table 3.1 Factor f, Calculated for Different Altitudes
Example
What is the airflow required to cool two adjustable
frequency drives (heat losses 295 W and 1430 W) running
simultaneously, mounted in an enclosure with an ambient
temperature peak of 37 °C (98.6 °F)?
1. The sum of the heat losses of both adjustable
frequency drives is 1725 W.
2.
Multiplying 1725 W by 3.3 m
m x K/h.
Subtracting 37 °C from 45 °C gives 8 °C (=8 K).
3.
4.
Dividing 5693 m x K/h by 8 K gives: 711.6 m
If the airflow is required in CFM, use the conversion 1 m
= 0.589 CFM.
For the example above, 711.6 m

3.1.4 Motor-generated Overvoltage

The DC voltage in the intermediate circuit (DC bus)
increases when the motor acts as a generator. This can
occur in two ways:
•
The load drives the motor when the adjustable
frequency drive is operated at a constant output
frequency. This is generally referred to as an
overhauling load.
•
During deceleration, if the inertia of the load is
high and the deceleration time of the drive is set
to a short value.
The adjustable frequency drive cannot regenerate energy
back to the input. Therefore, it limits the energy accepted
from the motor when set to enable autoramping. The
adjustable frequency drive attempts to do this by automat-
ically lengthening the ramp-down time if the overvoltage
occurs during deceleration. If this is unsuccessful, or if the
40
Specific heat of air Density of air
cp ρ
[kJ/kgK]
[kg/m
0.9480 1.225
0.9348 1.167
0.9250 1.112
0.8954 1.058
0.8728 1.006
0.8551 0.9568
0.8302 0.9091
0.8065 0.8633
3
x K/Wh gives 5693
3
/h = 418.85 CFM.
Danfoss A/S © 09/2014 All rights reserved.
®
VLT AQUA Drive FC 202
load drives the motor when operating at a constant
frequency, the drive shuts down and displays a fault when
a critical DC bus voltage level is reached.
Factor
f

3.1.5 Acoustic Noise

⋅K/Wh]
3 3
] [m
3.1
Acoustic noise from the adjustable frequency drive comes
3.3
from three sources:
3.5
3.8
•
4.1
•
4.4
•
4.8
5.2
See Table 7.60 for acoustic noise ratings.

3.1.6 Vibration and Shock

The adjustable frequency drive is tested according to a
procedure based on the IEC 68-2-6/34/35 and 36. These
tests subject the unit to 0.7 g forces, over the range of 18
to 1000 Hz randomly, in three directions, for two hours. All
Danfoss adjustable frequency drives comply 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.

3.1.7 Aggressive Atmospheres

3 h.
3.1.7.1 Gases
3
/h
Aggressive gases, such as hydrogen sulfide, chlorine, or
ammonia can damage adjustable frequency drive 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 are
recommended along with conformal-coated circuit boards.
See Table 3.2 for conformal-coating values.
NOTICE!
The adjustable frequency drive comes standard with
class 3C2 coating of circuit boards. On request, class 3C3
coating is available.
DC link (intermediate circuit) coils
RFI filter choke
Internal fans
MG20N622