Peak Voltage On Motor - Danfoss VLT 8000 AQUA series Operating Instructions Manual

Peak voltage on motor

When a transistor in the inverter is opened,
the voltage across the motor increases by a
dU/dt ratio that depends on:
- the motor cable (type, cross-section, length
screened or unscreened)
- inductance
The natural induction causes an overshot U
motor voltage before it stabilises itself at a level which
depends on the voltage in the intermediate circuit. The
rise time and the peak voltage U
life of the motor. If the peak voltage is too high, motors
without phase coil insulation are the ones that will
primarily be 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 will increase.
If very small motors are used without phase coil
insulation, it is recommended to fit a LC filter
after the frequency converter.
Typical values for the rise time and peak voltage
U are measured on the motor terminals
PEAK
between two phases.
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).
3.
Data are measured according to IEC 60034-17.
Cable lengths are in metres/feet.
VLT 8006-8011 / 380-480 V
Mains
Cable volt-
length age Rise time
0.5 µsec.
50m/164ft 500 V
1 µsec.
150m/492ft 500 V
0.6 µsec.
50m/164ft 380 V
150m/492ft 380 V 1.33
µsec.
MG.83.A2.02 - VLT is a registered Danfoss trademark
in the
PEAK
affect the service
PEAK
Peak
voltage dU/dt
1230 V 1968 V/µsec.
1270 V 1270 V/µsec.
1000 V 1333 V/µsec.
1000 V 602 V/µsec.
®
VLT 8000 AQUA
VLT 8016-8122 / 380-480 V
Mains
Cable volt-
length age Rise time
0.27 µsec.
32m/105ft 380 V
0.60 µsec.
70m/230ft 380 V
1.11 µsec.
132m/433ft 380 V
VLT 8152-8352 / 380-480 V
Mains
Cable volt-
length age Rise time
70m/230ft 400 V 0.34
µsec.
VLT 8452-8652 / 380-480 V
Mains
Cable volt-
length age Rise time
29m/95ft 500 V 0.71
µsec.
29m/95ft 400 V 0.61
µsec.
VLT 8002-8011 / 525-600 V
Mains
Cable volt-
length age Rise time
0.36 µsec.
35m/115ft 600 V
VLT 8016-8072 / 525-600 V
Mains
Cable volt-
length age Rise time
0.38 µsec.
35m/115ft 575 V
VLT 8052-8402 / 525-690 V
Cable Mains
length voltage Rise time
0.59 µsec.
25m/82ft 690 V
0.66 µsec.
25m/82ft 575 V
1.72 µsec.
1)
25m/82ft 690 V
VLT 8502-8652 / 525-690 V
Cable Mains
length voltage Rise time
0.57 µsec.
25m/82ft 690 V
0.25 µsec.
25m/82ft 575 V
1.13 µsec.
1)
25m/82ft 690 V
1) With Danfoss dU/dt filter.
Peak
voltage dU/dt
950 V 2794 V/µsec.
950 V 1267 V/µsec.
950 V 685 V/µsec.
Peak
voltage dU/dt
1040 V 2447 V/µsec.
Peak
voltage dU/dt
1165 V 1389 V/µsec.
942 V 1233 V/µsec.
Peak
voltage dU/dt
1360 V 3022 V/µsec.
Peak
voltage dU/dt
1430 V 3011 V/µsec.
Peak
voltage dU/dt
1425 1983 V/µsec.
1159 1428 V/µsec.
1329 640 V/µsec.
Peak
voltage dU/dt
1540 2230 V/µsec.
2510 V/µsec.
1629 1149 V/µsec.
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