Specifications

Enclosure type
At reduced fan speed
(50%) [dBA]
Full fan speed [dBA]
A2 51 60
A3 51 60
A4 50 55
A5 54 63
B1 61 67
B2 58 70
B3 59.4 70.5
B4 53 62.8
C1 52 62
C2 55 65
C3 56.4 67.3
C4 - -
Table 9.10 Measured Values
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
screened or unscreened)
•
inductance
The natural induction causes an overshoot U
PEAK
in the
motor voltage before it stabilises itself at a level
depending on the voltage in the intermediate circuit. The
rise time and the peak voltage U
PEAK
affect the service life
of the motor. If the peak voltage is too high, especially
motors without 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 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
PEAK
= DC link voltage x 1.9
(DC link voltage = Mains voltage x 1.35).
3.
dU / dt =
0.8 × U
PEAK
Risetime
Data are measured according to IEC 60034-17.
Cable lengths are in metres.
Cable
length [m]
Mains
voltage [V]
Rise time
[μsec]
Vpeak
[kV]
dU/dt
[kV/μsec]
36 240 0.226 0.616 2.142
50 240 0.262 0.626 1.908
100 240 0.650 0.614 0.757
150 240 0.745 0.612 0.655
Table 9.11 Frequency converter, P5K5, T2
Cable
length [m]
Mains
voltage [V]
Rise time
[μsec]
Vpeak
[kV]
dU/dt
[kV/μsec]
5 230 0.13 0.510 3.090
50 230 0.23 0.590 2.034
100 230 0.54 0.580 0.865
150 230 0.66 0.560 0.674
Table 9.12 Frequency converter, P7K5, T2
Cable
length [m]
Rise time
[μsec]
Vpeak
[kV]
dU/dt
[kV/μsec]
36 240 0.264 0.624 1.894
136 240 0.536 0.596 0.896
150 240 0.568 0.568 0.806
Table 9.13 Frequency converter, P11K, T2
General Specifications and ... Design Guide
MG11BC02 Danfoss A/S © Rev. 06/2014 All rights reserved. 161
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