Acoustic Noise; Du/Dt Conditions - Danfoss VLT Midi Drive FC 280 Design Manual

Specifications

7.10 Acoustic Noise

The acoustic noise from the frequency converter comes
from 3 sources:
•
DC intermediate circuit coils.
•
Integral fan.
•
RFI filter choke.
The typical values measured at a distance of 1 m (3.3 ft)
from the unit:
Enclosure size 80% fan
[kW (hp)] speed [dBA]
K1
0.37–2.2 41.4
(0.5–3.0)
K2
50.3
3.0–5.5 (4.0–7.5)
K3
51
7.5 (10)
K4
59
11–15 (15–20)
K5
64.6
18.5–22 (25–30)
Table 7.5 Typical Measured Values

7.11 dU/dt Conditions

When a transistor in the frequency converter bridge
switches, the voltage across the motor increases by a
dU/dt ratio depending on the following factors:
•
The motor cable type.
•
The cross-section of the motor cable.
•
The length of the motor cable.
•
Whether the motor cable is shielded or not.
•
Inductance.
The natural induction causes an overshoot U
motor voltage before it stabilizes itself at a level
depending on the voltage in the DC link. The rise time and
the peak voltage U affect the service life of the motor.
PEAK
If the peak voltage is too high, motors without phase coil
insulation are affected. The longer the motor cable, the
higher the rise time and peak voltage.
Switching of the IGBTs cause peak voltage on the motor
terminals. The FC 280 complies with IEC 60034-25
regarding motors designed to be controlled by frequency
converters. The FC 280 also complies with IEC 60034-17
regarding Norm motors controlled by frequency converters.
The following dU/dt data are measured at the motor
terminal side:
MG07B102
Design Guide
Full fan speed Background
[dBA] noise
42.7 33
54.3 32.9
54.2 33
61.1 32.9
65.6 32.9
in the
PEAK
Danfoss A/S © 03/2016 All rights reserved.
Cable Mains
Rise time
length voltage
[m (ft)] [V] [μsec]
5 (16.4) 400 0.0904
50 (164) 400 0.292
5 (16.4) 480 0.108
50 (164) 480 0.32
Table 7.6 dU/dt Data for FC 280, 2.2 kW (3.0 hp), 3x380–480 V
Cable Mains
length voltage Rise time
[m (ft)] [V] [μsec]
5 (16.4) 400 0.096
50 (164) 400 0.306
5 (16.4) 480 0.118
50 (164) 480 0.308
Table 7.7 dU/dt Data for FC 280, 5.5 kW (7.5 hp), 3x380–480 V
Cable Mains
length voltage Rise time
[m (ft)] [V] [μsec]
5 (16.4) 400 0.128
50 (164) 400 0.354
5 (16.4) 480 0.134
50 (164) 480 0.36
Table 7.8 dU/dt Data for FC 280, 7.5 kW (10 hp), 3x380–480 V
Cable Mains
Rise time
length voltage
[m (ft)] [V] [μsec]
5 (16.4) 400 0.26
50 (164) 400 0.738
5 (16.4) 480 0.334
50 (164) 480 0.692
Table 7.9 dU/dt Data for FC 280, 15 kW (20 hp), 3x380–480 V
Cable Mains
length voltage Rise time
[m (ft)] [V] [μsec]
5 (16.4) 400 0.258
50 (164) 400 0.38
5 (16.4) 480 0.258
50 (164) 480 0.4
Table 7.10 dU/dt Data for FC 280, 22 kW (30 hp), 3x380–480 V
Cable Mains
length voltage Rise time
[m (ft)] [V] [μsec]
5 (16.4) 240 0.0712
50 (164) 240 0.224
Table 7.11 dU/dt Data for FC 280, 1.5 kW (2.0 hp), 3x200–240 V
dU/dt
U
PEAK
[kV] [kV/μsec]
0.718 6.41
1.05 2.84
0.835 6.20
1.25 3.09
U dU/dt
PEAK
[kV] [kV/μsec]
0.632 5.31
0.99 2.58
0.694 4.67
1.18 3.05
U dU/dt
PEAK
[kV] [kV/μsec]
0.732 4.54
1.01 2.27
0.835 5.03
1.21 2.69
dU/dt
U
PEAK
[kV] [kV/μsec]
0.84 2.57
1.07 1.15
0.99 2.36
1.25 1.44
U dU/dt
PEAK
[kV] [kV/μsec]
0.652 2.01
1.03 2.15
0.752 2.34
1.23 2.42
U dU/dt
PEAK
[kV] [kV/μsec]
0.484 5.44
0.594 2.11
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