Peak Voltage On Motor - Danfoss FC 102 Design Manual

General Specifications and ...
At reduced fan speed
Enclosure type
(50%) [dBA]
A2 51
A3 51
A4 50
A5 54
B1 61
B2 58
B3 59.4
B4 53
C1 52
C2 55
C3 56.4
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
motor voltage before it stabilises itself at a level
Cable Mains
length [m] voltage [V]
36 240
50 240
100 240
150 240
Table 9.11 Frequency converter, P5K5, T2
Cable Mains
length [m] voltage [V]
5 230
50 230
100 230
150 230
Table 9.12 Frequency converter, P7K5, T2
Cable
length [m]
36 240
136 240
150 240
Table 9.13 Frequency converter, P11K, T2
MG11BC02
Design Guide
depending on the voltage in the intermediate circuit. The
Full fan speed [dBA]
rise time and the peak voltage U
of the motor. If the peak voltage is too high, especially
60
motors without phase coil insulation are affected. If the
60
motor cable is short (a few metres), the rise time and peak
55
voltage are lower.
63
If the motor cable is long (100 m), the rise time and peak
67
voltage increases.
70
70.5
In motors without phase insulation paper or other
62.8
insulation reinforcement suitable for operation with
62
voltage supply (such as a frequency converter), fit a sine-
65
wave filter on the output of the frequency converter.
67.3
-
To obtain approximate values for cable lengths and
voltages not mentioned below, use the following rules of
thumb:
Data are measured according to IEC 60034-17.
in the Cable lengths are in metres.
PEAK
Rise time
[μsec]
0.226
0.262
0.650
0.745
Rise time
[μsec]
0.13
0.23
0.54
0.66
Rise time
[μsec]
0.264
0.536
0.568
Danfoss A/S © Rev. 06/2014 All rights reserved.
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 × UPEAK
3.
dU / dt =
Risetime
Vpeak dU/dt
[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
dU/dt
Vpeak
[kV] [kV/μsec]
0.624 1.894
0.596 0.896
0.568 0.806
affect the service life
PEAK
161
9 9