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

System Integration
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 2 ways:
•
The load drives the motor when the frequency
converter 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 converter is
set to a short value.
The frequency converter cannot regenerate energy back to
the input. Therefore, it limits the energy accepted from the
motor when set to enable autoramping. The frequency
converter attempts to do this by automatically lengthening
the ramp-down time, if the overvoltage occurs during
deceleration. If this is unsuccessful, or if the load drives the
motor when operating at a constant frequency, the
converter shuts down and displays a fault when a critical
DC bus voltage level is reached.

3.1.5 Acoustic Noise

Acoustic noise from the frequency converter comes from 3
sources:
•
DC-link (intermediate circuit) coils
•
RFI filter choke
•
Internal fans
See Table 7.60 for acoustic noise ratings.

3.1.6 Vibration and Shock

The frequency converter 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 3 directions, for 2 hours. All Danfoss
frequency converters 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.
MG20N602
Design Guide
3
/h
3
/h = 418.85 CFM.
Danfoss A/S © 09/2014 All rights reserved.

3.1.7 Aggressive Atmospheres

3.1.7.1 Gases
Aggressive gases, such as hydrogen sulphide, chlorine, or
ammonia can damage frequency converter 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 frequency converter comes standard with class 3C2
coating of circuit boards. On request, class 3C3 coating is
available.
3C1
Gas type Unit
Sea salt n/a None Salt mist
Sulphur oxides 3 0.1
mg/m
Hydrogen 3 0.01
mg/m
sulphide
Chlorine 0.01
mg/m 3
Hydrogen 3 0.01
mg/m
chloride
Hydrogen 0.003 0.01
mg/m 3
fluoride
Ammonia 3 0.3
mg/m
Ozone 3 0.01
mg/m
Nitrogen 0.1
mg/m 3
Table 3.2 Conformal-coating Class Ratings
1) Maximum values are transient peak values not to exceed 30
minutes per day.
3.1.7.2 Dust Exposure
Installation of frequency converters in environments with
high dust exposure is often unavoidable. Dust affects wall-
or frame-mounted units with IP55 or IP66 protection
ratings, and also cabinet-mounted devices with IP21 or
IP20 protection ratings. Consider the 3 aspects described in
this section when frequency converters are installed in
such environments.
Class
3C2 3C3
Average Max. Average Max.
value value value value
1) 1)
Salt mist
0.3 1.0 5.0 10
0.1 0.5 3.0 10
0.1 0.03 0.3 1.0
0.1 0.5 1.0 5.0
0.03 0.1 3.0
1.0 3.0 10 35
0.05 0.1 0.1 0.3
0.5 1.0 3.0 9.0
39
3 3