Acoustic Noise; Du/Dt Conditions - Danfoss FC 300 Design Manual

4 AutomationDrive FC 300 Selection

4.7.1 Acoustic Noise

The acoustic noise from the frequency converter comes from three sources:
1. DC intermediate circuit coils.
2. Integral fan.
3. RFI filter choke.
The typical values measured at a distance of 1 m from the unit:
Frame size
A1
4
A2
A3
A5
B1
B2
C1
C2
D1+D3
D2+D4
E1/E2 *
E1/E2 **
F1/F2/F3/F4
* 250 kW, 380-500 VAC and 355-400 kW, 525-690 VAC only
** Remaining E1+E2 power sizes.
*** For D and E sizes, reduced fan speed is at 87%.

4.8.1 du/dt Conditions

NB!
380-690V
To avoid premature ageing of motors (without phase insulation paper or other insulation reinforcement) not designed for frequency
converter operation, Danfoss strongly recommend to fit a du/dt filter or a Sine-Wave filter on the output of the frequency converter.
For further information about du/dt and Sine-Wave filters see the Output Filters Design Guide - MG90NYXX.
When a transistor in the inverter bridge switches, the voltage across the motor increases by a du/dt ratio depending on:
- the motor cable (type, cross-section, length screened or unscreened)
- inductance
The natural induction causes an overshoot U
circuit. The rise time and the peak voltage U
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.
Peak voltage on the motor terminals is caused by the switching of the IGBTs. The AutomationDrive FC 300 complies with the demands of IEC 60034-25
regarding motors designed to be controlled by frequency converters. The AutomationDrive FC 300 also complies with IEC 60034-17 regarding Norm
motors controlled by frequency converters
Measured values from lab tests:
AutomationDrive FC 300, P5K5T2
Cable
length [m]
5
50
100
150
84
At reduced fan speed (50%) [dBA] ***
in the motor voltage before it stabilises itself at a level depending on the voltage in the intermediate
PEAK
affect the service life of the motor. If the peak voltage is too high, especially motors without phase coil
PEAK
Mains Rise time
voltage [V] [μsec]
240 0.13
240 0.23
240 0.54
240 0.66
MG.33.BC.02 - VLT
51
51
51
54
61
58
52
55
74
73
73
82
78
Upeak du/dt
[kV] [kV/μsec]
0.510 3.090
2.034
0.580 0.865
0.560 0.674
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FC 300 Design Guide
Full fan speed [dBA]
60
60
60
63
67
70
62
65
76
74
74
83
80