Acoustic Noise; Peak Voltage On Motor - Danfoss VLT FC 102 Series Design Manual

General Specifications and ...

9.4 Acoustic noise

The acoustic noise from the adjustable frequency drive
originates from three sources:
•
DC intermediate circuit coils.
•
Integrated fan.
•
RFI filter choke.
Typical values are measured at a distance of 3.3 ft. [1 m]
from the unit:
Enclosure type
A2
A3
A4
A5
B1
B2
B3
B4
9 9
C1
C2
C3
C4
Table 9.11 Measured values
Cable length
(ft [m])
120 [36]
164 [50]
330 [100]
500 [150]
Table 9.12 Adjustable frequency drive, P5K5, T2
Cable length
(ft [m])
16.4 [5]
164 [50]
330 [100]
500 [150]
Table 9.13 Adjustable frequency drive, P7K5, T2
182
Design Guide
At reduced fan
Full fan speed
speed (50%)
[dBA]
[dBA]
51 60
51 60
50 55
54 63
61 67
58 70
59.4 70.5
53 62.8
52 62
55 65
56.4 67.3
- -
Rise time
AC linevoltage
[V] [μsec]
240 0.226
240 0.262
240 0.650
240 0.745
Rise time
AC linevoltage
[V] [μsec]
230 0.13
230 0.23
230 0.54
230 0.66
Danfoss A/S © Rev. 06/2014 All rights reserved.

9.5 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,
shielded or non-shielded)
•
inductance
The natural induction causes an overshoot U
motor voltage before it stabilizes itself at a level
depending on the voltage in the intermediate circuit. The
rise time and the peak voltage U
of the motor. If the peak voltage is too high, motors
without phase coil insulation are especially affected. If the
motor cable is short (by a few yards), the rise time and
peak voltage are lower. If the motor cable is long (330 ft
[100 m]), the rise time and peak voltage increase. In
motors without phase insulation paper or other insulation
reinforcement suitable for operation with the voltage
supply (such as an adjustable frequency drive), fit a sine-
wave filter on the output of the adjustable frequency drive.
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 = AC line voltage x 1.35).
UPEAK
0.8 ×
3.
dU / dt =
Rise time
Data are measured according to IEC 60034-17.
Cable lengths are in meters.
dU/dt
Vpeak
[kV] [kV/μsec]
0.616 2.142
0.626 1.908
0.614 0.757
0.612 0.655
dU/dt
Vpeak
[kV] [kV/μsec]
0.510 3.090
0.590 2.034
0.580 0.865
0.560 0.674
in the
PEAK
affect the service life
PEAK
MG11BC22