Special Conditions; Purpose Of Derating - Danfoss VLT Aqua Drive FC 202 Operating Instructions Manual

9. Specifications
The acoustic noise from the frequency converter comes from three sources:
1.
2.
3.
The typical values measured at a distance of 1 m from the unit:
A2
A3
A5
B1
B2
C1
C2
When a transistor in the inverter bridge switches, the voltage across the motor in-
creases by a du/dt ratio depending on:
-
-
The natural induction causes an overshoot U
9
a level depending on the voltage in the intermediate circuit. The rise time and the peak voltage
U
PEAK
phase coil insulation are affected. If the motor cable is short (a few metres), the rise time and
peak voltage are lower.
If the motor cable is long (100 m), the rise time and peak voltage are higher.
In motors without phase insulation paper or other insulation reinforcement suitable for operation
with voltage supply (such as a frequency converter), fit a du/dt filter or a sine-wave filter on the
output of the frequency converter.

9.2. Special Conditions

9.2.1. Purpose of derating

Derating must be taken into account when using the frequency converter at low air pressure
(heights), at low speeds, with long motor cables, cables with a large cross section or at high
ambient temperature. The required action is described in this section.
9.2.2. Derating for Ambient Temperature
The average temperature (T
the maximum allowed ambient temperature (T
If the frequency converter is operated at high ambient temperatures, the continuous output cur-
rent should be decreased.
The derating depends on the switching pattern, which can be set to 60 PWM or SFAVM in pa-
rameter 14-00.
136
DC intermediate circuit coils.
Integral fan.
RFI filter choke.
Encapsulation
the motor cable (type, cross-section, length screened or unscreened)
inductance
affect the service life of the motor. If the peak voltage is too high, especially motors without
AMB, AVG
MG.20.M2.02 - VLT
At reduced fan speed
(50%) [dBA]
51
51
-
61
58
52
55
in the motor voltage before it stabilises itself at
PEAK
) measured over 24 hours must be at least 5 °C lower than
).
AMB,MAX
®
is a registered Danfoss trademark
®
VLT
Operating Instructions
Full fan speed [dBA]
60
60
54
67
70
62
65
AQUA Drive