GE AF-600 FP Design Manual page 151

7.4 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:
Unit size
12
13
15
21
22
23
24
31
32
33
34
41/43
7 42/44
51/52*
51/52**
61/62/63/64
* 315 kW, 380-480 VAC and 450-500 kW, 525-690 VAC only!
** Remaining 51/52 unit sizes.
*** For 4x, 5x and 6x sizes, reduced fan speed is at 87%, measured at 200 V.
7.5 Peak Voltage on Motor
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
rise time and the peak voltage U
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 increases.
In motors without phase insulation paper or other insulation reinforcement suitable for operation with voltage supply (such as a frequency converter), fit a sine-
wave filter on the output of the frequency converter.
To obtain approximate values for cable lengths and voltages not mentioned below, use the following rules of thumb:
1. Rise time increases/decreases proportionally with cable length.
2. U = DC link voltage x 1.9
PEAK
(DC link voltage = Mains voltage x 1.35).
/
0.8 ×
3.
dU dt
=
Risetime
Data are measured according to IEC 60034-17.
Cable lengths are in metres.
150
At reduced fan speed (50%) [dBA] ***
in the motor voltage before it stabilizes itself at a level depending on the voltage in the intermediate circuit. The
PEAK
affect the service life of the motor. If the peak voltage is too high, especially motors without phase coil insulation are affected.
PEAK
U PEAK
51
51
54
61
58
59.4
53
52
55
56.4
-
74
73
73
82
78
AF-600 FP Design Guide
Full fan speed [dBA]
60
60
63
67
70
70.5
62.8
62
65
67.3
-
76
74
74
83
80